_B_A_S_H(1)                     General Commands Manual                    _B_A_S_H(1)

NNAAMMEE
       bash - GNU Bourne-Again SHell

SSYYNNOOPPSSIISS
       bbaasshh [options] [command_string | file]

CCOOPPYYRRIIGGHHTT
       Bash is Copyright (C) 1989-2025 by the Free Software Foundation, Inc.

DDEESSCCRRIIPPTTIIOONN
       BBaasshh is a command language interpreter that executes commands read from
       the standard input, from a string, or from a file.  It is a reimplemen-
       tation  and  extension of the Bourne shell, the historical Unix command
       language interpreter.  BBaasshh also incorporates useful features from  the
       _K_o_r_n and _C shells (kksshh and ccsshh).

       POSIX  is  the  name for a family of computing standards based on Unix.
       BBaasshh is intended to be a conformant implementation  of  the  Shell  and
       Utilities  portion  of  the  IEEE  POSIX  specification  (IEEE Standard
       1003.1).  BBaasshh POSIX mode (hereafter referred to as _p_o_s_i_x _m_o_d_e) changes
       the shell's behavior where its default operation differs from the stan-
       dard to strictly conform to the standard.  See SSEEEE  AALLSSOO  below  for  a
       reference  to a document that details how posix mode affects bbaasshh's be-
       havior.  BBaasshh can be configured to be POSIX-conformant by default.

OOPPTTIIOONNSS
       All of the single-character shell options documented in the description
       of the sseett builtin command, including --oo, can be used as  options  when
       the  shell  is invoked.  In addition, bbaasshh interprets the following op-
       tions when it is invoked:

       --cc        If the --cc option is present, then commands are read from  the
                 first non-option argument _c_o_m_m_a_n_d___s_t_r_i_n_g.  If there are argu-
                 ments  after  the  _c_o_m_m_a_n_d___s_t_r_i_n_g,  the first argument is as-
                 signed to $$00 and any remaining arguments are assigned to  the
                 positional parameters.  The assignment to $$00 sets the name of
                 the shell, which is used in warning and error messages.

       --ii        If the --ii option is present, the shell is _i_n_t_e_r_a_c_t_i_v_e.

       --ll        Make bbaasshh act as if it had been invoked as a login shell (see
                 IINNVVOOCCAATTIIOONN below).

       --rr        If  the  --rr  option  is present, the shell becomes _r_e_s_t_r_i_c_t_e_d
                 (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).

       --ss        If the --ss option is present, or if no arguments remain  after
                 option processing, the shell reads commands from the standard
                 input.   This  option  allows the positional parameters to be
                 set when invoking an interactive shell or when reading  input
                 through a pipe.

       --DD        Print  a  list  of all double-quoted strings preceded by $$ on
                 the standard output.  These are the strings that are  subject
                 to  language  translation when the current locale is not CC or
                 PPOOSSIIXX.  This implies the --nn option; no commands will be  exe-
                 cuted.

       [[--++]]OO [[_s_h_o_p_t___o_p_t_i_o_n]]
                 _s_h_o_p_t___o_p_t_i_o_n  is  one  of  the  shell options accepted by the
                 sshhoopptt  builtin  (see  SSHHEELLLL  BBUUIILLTTIINN  CCOOMMMMAANNDDSS  below).    If
                 _s_h_o_p_t___o_p_t_i_o_n is present, --OO sets the value of that option; ++OO
                 unsets  it.  If _s_h_o_p_t___o_p_t_i_o_n is not supplied, bbaasshh prints the
                 names and values of the shell options accepted  by  sshhoopptt  on
                 the  standard  output.   If  the invocation option is ++OO, the
                 output is displayed in a format that may be reused as input.

       ----        A ---- signals the end of options and disables  further  option
                 processing.   Any  arguments  after  the  ---- are treated as a
                 shell script filename (see below)  and  arguments  passed  to
                 that script.  An argument of -- is equivalent to ----.

       BBaasshh  also  interprets  a number of multi-character options.  These op-
       tions must appear on the command line before the  single-character  op-
       tions to be recognized.

       ----ddeebbuuggggeerr
              Arrange for the debugger profile to be executed before the shell
              starts.   Turns  on extended debugging mode (see the description
              of the eexxttddeebbuugg option to the sshhoopptt builtin below).

       ----dduummpp--ppoo--ssttrriinnggss
              Equivalent to --DD, but the output is  in  the  GNU  _g_e_t_t_e_x_t  "po"
              (portable object) file format.

       ----dduummpp--ssttrriinnggss
              Equivalent to --DD.

       ----hheellpp Display  a  usage  message  on standard output and exit success-
              fully.

       ----iinniitt--ffiillee _f_i_l_e
       ----rrccffiillee _f_i_l_e
              Execute commands from _f_i_l_e instead of the standard personal ini-
              tialization file _~_/_._b_a_s_h_r_c if the shell is interactive (see  IINN--
              VVOOCCAATTIIOONN below).

       ----llooggiinn
              Equivalent to --ll.

       ----nnooeeddiittiinngg
              Do  not  use the GNU rreeaaddlliinnee library to read command lines when
              the shell is interactive.

       ----nnoopprrooffiillee
              Do not read either the system-wide startup file _/_e_t_c_/_p_r_o_f_i_l_e  or
              any   of  the  personal  initialization  files  _~_/_._b_a_s_h___p_r_o_f_i_l_e,
              _~_/_._b_a_s_h___l_o_g_i_n, or _~_/_._p_r_o_f_i_l_e.   By  default,  bbaasshh  reads  these
              files  when  it  is invoked as a login shell (see IINNVVOOCCAATTIIOONN be-
              low).

       ----nnoorrcc Do  not  read  and  execute  the  personal  initialization  file
              _~_/_._b_a_s_h_r_c if the shell is interactive.  This option is on by de-
              fault if the shell is invoked as sshh.

       ----ppoossiixx
              Enable posix mode; change the behavior of bbaasshh where the default
              operation differs from the POSIX standard to match the standard.

       ----rreessttrriicctteedd
              The shell becomes restricted (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).

       ----vveerrbboossee
              Equivalent to --vv.

       ----vveerrssiioonn
              Show  version information for this instance of bbaasshh on the stan-
              dard output and exit successfully.

AARRGGUUMMEENNTTSS
       If arguments remain after option processing, and neither the --cc nor the
       --ss option has been supplied, the first argument is treated as the  name
       of a file containing shell commands (a _s_h_e_l_l _s_c_r_i_p_t).  When bbaasshh is in-
       voked in this fashion, $$00 is set to the name of the file, and the posi-
       tional  parameters  are set to the remaining arguments.  BBaasshh reads and
       executes commands from this file, then exits.  BBaasshh's  exit  status  is
       the exit status of the last command executed in the script.  If no com-
       mands  are executed, the exit status is 0.  BBaasshh first attempts to open
       the file in the current directory, and, if no file is  found,  searches
       the directories in PPAATTHH for the script.

IINNVVOOCCAATTIIOONN
       A  _l_o_g_i_n _s_h_e_l_l is one whose first character of argument zero is a --, or
       one started with the ----llooggiinn option.

       An _i_n_t_e_r_a_c_t_i_v_e _s_h_e_l_l is one started without non-option  arguments  (un-
       less --ss is specified) and without the --cc option, and whose standard in-
       put  and  standard error are both connected to terminals (as determined
       by _i_s_a_t_t_y(3)), or one started with the --ii option.  BBaasshh sets PPSS11 and $$--
       includes ii if the shell is interactive, so a shell script or a  startup
       file can test this state.

       The  following paragraphs describe how bbaasshh executes its startup files.
       If any of the files exist but cannot be read, bbaasshh  reports  an  error.
       Tildes  are expanded in filenames as described below under TTiillddee EExxppaann--
       ssiioonn in the EEXXPPAANNSSIIOONN section.

       When bbaasshh is invoked as an interactive login shell, or as a  non-inter-
       active  shell with the ----llooggiinn option, it first reads and executes com-
       mands from the file _/_e_t_c_/_p_r_o_f_i_l_e, if that file exists.   After  reading
       that file, it looks for _~_/_._b_a_s_h___p_r_o_f_i_l_e, _~_/_._b_a_s_h___l_o_g_i_n, and _~_/_._p_r_o_f_i_l_e,
       in  that order, and reads and executes commands from the first one that
       exists and is readable.  The ----nnoopprrooffiillee option may be  used  when  the
       shell is started to inhibit this behavior.

       When an interactive login shell exits, or a non-interactive login shell
       executes  the  eexxiitt  builtin  command, bbaasshh reads and executes commands
       from the file _~_/_._b_a_s_h___l_o_g_o_u_t, if it exists.

       When an interactive shell that is not a login shell  is  started,  bbaasshh
       reads  and  executes commands from _~_/_._b_a_s_h_r_c, if that file exists.  The
       ----nnoorrcc option inhibits this behavior.  The ----rrccffiillee _f_i_l_e option  causes
       bbaasshh to use _f_i_l_e instead of _~_/_._b_a_s_h_r_c.

       When  bbaasshh is started non-interactively, to run a shell script, for ex-
       ample, it looks for the variable BBAASSHH__EENNVV in the  environment,  expands
       its  value if it appears there, and uses the expanded value as the name
       of a file to read and execute.  BBaasshh behaves as if the  following  com-
       mand were executed:

              if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi

       but does not use the value of the PPAATTHH variable to search for the file-
       name.

       If  bbaasshh is invoked with the name sshh, it tries to mimic the startup be-
       havior of historical versions of sshh as closely as possible, while  con-
       forming  to the POSIX standard as well.  When invoked as an interactive
       login shell, or a non-interactive shell with  the  ----llooggiinn  option,  it
       first  attempts  to  read  and  execute  commands from _/_e_t_c_/_p_r_o_f_i_l_e and
       _~_/_._p_r_o_f_i_l_e, in that order.  The ----nnoopprrooffiillee option inhibits this behav-
       ior.  When invoked as an interactive shell with the name sshh, bbaasshh looks
       for the variable EENNVV, expands its value if it is defined, and uses  the
       expanded  value  as  the  name  of a file to read and execute.  Since a
       shell invoked as sshh does not attempt to read and execute commands  from
       any  other startup files, the ----rrccffiillee option has no effect.  A non-in-
       teractive shell invoked with the name sshh does not attempt to  read  any
       other startup files.

       When  invoked  as  sshh, bbaasshh enters posix mode after reading the startup
       files.

       When bbaasshh is started in posix mode, as with the  ----ppoossiixx  command  line
       option, it follows the POSIX standard for startup files.  In this mode,
       interactive  shells  expand  the EENNVV variable and read and execute com-
       mands from the file whose name is the expanded value.  No other startup
       files are read.

       BBaasshh attempts to determine when it is being run with its standard input
       connected to a network connection, as when executed by  the  historical
       and  rarely-seen remote shell daemon, usually _r_s_h_d, or the secure shell
       daemon _s_s_h_d.  If bbaasshh determines it is being run  non-interactively  in
       this  fashion,  it  reads and executes commands from _~_/_._b_a_s_h_r_c, if that
       file exists and is readable.  BBaasshh does not read this file  if  invoked
       as  sshh.  The ----nnoorrcc option inhibits this behavior, and the ----rrccffiillee op-
       tion makes bbaasshh use a different file instead of _~_/_._b_a_s_h_r_c, but  neither
       _r_s_h_d  nor  _s_s_h_d  generally invoke the shell with those options or allow
       them to be specified.

       If the shell is started with the effective user (group) id not equal to
       the real user (group) id, and the --pp option is not supplied, no startup
       files are read, shell functions are not inherited from the environment,
       the SSHHEELLLLOOPPTTSS, BBAASSHHOOPPTTSS, CCDDPPAATTHH, and GGLLOOBBIIGGNNOORREE variables, if they  ap-
       pear  in the environment, are ignored, and the effective user id is set
       to the real user id.  If the --pp option is supplied at  invocation,  the
       startup behavior is the same, but the effective user id is not reset.

DDEEFFIINNIITTIIOONNSS
       The  following  definitions  are used throughout the rest of this docu-
       ment.
       bbllaannkk  A space or tab.
       wwhhiitteessppaaccee
              A character belonging to the ssppaaccee character class in  the  cur-
              rent locale, or for which _i_s_s_p_a_c_e(3) returns true.
       wwoorrdd   A  sequence  of  characters  considered  as a single unit by the
              shell.  Also known as a ttookkeenn.
       nnaammee   A _w_o_r_d consisting only of  alphanumeric  characters  and  under-
              scores,  and beginning with an alphabetic character or an under-
              score.  Also referred to as an iiddeennttiiffiieerr.
       mmeettaacchhaarraacctteerr
              A character that, when unquoted, separates words.   One  of  the
              following:
              ||  && ;; (( )) << >> ssppaaccee ttaabb nneewwlliinnee
       ccoonnttrrooll ooppeerraattoorr
              A _t_o_k_e_n that performs a control function.  It is one of the fol-
              lowing symbols:
              |||| && &&&& ;; ;;;; ;;&& ;;;;&& (( )) || ||&& <<nneewwlliinnee>>

RREESSEERRVVEEDD WWOORRDDSS
       _R_e_s_e_r_v_e_d _w_o_r_d_s are words that have a special meaning to the shell.  The
       following words are recognized as reserved when unquoted and either the
       first  word of a command (see SSHHEELLLL GGRRAAMMMMAARR below), the third word of a
       ccaassee or sseelleecctt command (only iinn is valid), or the third word of  a  ffoorr
       command (only iinn and ddoo are valid):

       !!  ccaassee   ccoopprroocc   ddoo  ddoonnee eelliiff eellssee eessaacc ffii ffoorr ffuunnccttiioonn iiff iinn sseelleecctt
       tthheenn uunnttiill wwhhiillee {{ }} ttiimmee [[[[ ]]]]

SSHHEELLLL GGRRAAMMMMAARR
       This section describes the syntax of the various forms  of  shell  com-
       mands.

   SSiimmppllee CCoommmmaannddss
       A  _s_i_m_p_l_e  _c_o_m_m_a_n_d  is a sequence of optional variable assignments fol-
       lowed by bbllaannkk-separated words and redirections, and  terminated  by  a
       _c_o_n_t_r_o_l _o_p_e_r_a_t_o_r.  The first word specifies the command to be executed,
       and  is passed as argument zero.  The remaining words are passed as ar-
       guments to the invoked command.

       The return value of a _s_i_m_p_l_e _c_o_m_m_a_n_d is its exit status,  or  128+_n  if
       the command is terminated by signal _n.

   PPiippeelliinneess
       A  _p_i_p_e_l_i_n_e  is  a sequence of one or more commands separated by one of
       the control operators || or ||&&.  The format for a pipeline is:

              [ttiimmee [--pp]] [ ! ] _c_o_m_m_a_n_d_1 [ [|||||&&] _c_o_m_m_a_n_d_2 ... ]

       The standard output of _c_o_m_m_a_n_d_1 is connected via a pipe to the standard
       input of _c_o_m_m_a_n_d_2.  This connection is performed  before  any  redirec-
       tions  specified  by the _c_o_m_m_a_n_d_1(see RREEDDIIRREECCTTIIOONN below).  If ||&& is the
       pipeline operator, _c_o_m_m_a_n_d_1's standard error, in addition to its  stan-
       dard  output,  is  connected  to  _c_o_m_m_a_n_d_2's standard input through the
       pipe; it is shorthand for 22>>&&11 ||.  This  implicit  redirection  of  the
       standard  error  to the standard output is performed after any redirec-
       tions specified by _c_o_m_m_a_n_d_1.

       The return status of a pipeline is the exit status of the last command,
       unless the ppiippeeffaaiill option is enabled.  If  ppiippeeffaaiill  is  enabled,  the
       pipeline's  return  status is the value of the last (rightmost) command
       to exit with a non-zero status, or zero if all commands  exit  success-
       fully.  If the reserved word !!  precedes a pipeline, the exit status of
       that  pipeline  is the logical negation of the exit status as described
       above.  If a pipeline is executed synchronously, the  shell  waits  for
       all commands in the pipeline to terminate before returning a value.

       If  the  ttiimmee  reserved word precedes a pipeline, the shell reports the
       elapsed as well as user and system time consumed by its execution  when
       the  pipeline  terminates.   The --pp option changes the output format to
       that specified by POSIX.  When the shell is in posix mode, it does  not
       recognize  ttiimmee as a reserved word if the next token begins with a "-".
       The value of the TTIIMMEEFFOORRMMAATT variable is a format string that  specifies
       how  the timing information should be displayed; see the description of
       TTIIMMEEFFOORRMMAATT below under SShheellll VVaarriiaabblleess.

       When the shell is in posix mode, ttiimmee may appear by itself as the  only
       word  in  a simple command.  In this case, the shell displays the total
       user and system time consumed by the shell and its children.  The TTIIMMEE--
       FFOORRMMAATT variable specifies the format of the time information.

       Each command in a multi-command pipeline, where pipes are  created,  is
       executed  in a _s_u_b_s_h_e_l_l, which is a separate process.  See CCOOMMMMAANNDD EEXXEE--
       CCUUTTIIOONN EENNVVIIRROONNMMEENNTT for a description of subshells and a subshell  envi-
       ronment.   If  the  llaassttppiippee  option is enabled using the sshhoopptt builtin
       (see the description of sshhoopptt below), and job control  is  not  active,
       the last element of a pipeline may be run by the shell process.

   LLiissttss
       A  _l_i_s_t  is a sequence of one or more pipelines separated by one of the
       operators ;;, &&, &&&&, or ||||, and optionally terminated by one of ;;, &&, or
       <<nneewwlliinnee>>.

       Of these list operators, &&&& and |||| have equal precedence, followed by ;;
       and &&, which have equal precedence.

       A sequence of one or more newlines may appear in a _l_i_s_t  instead  of  a
       semicolon to delimit commands.

       If  a  command  is terminated by the control operator &&, the shell exe-
       cutes the command in the _b_a_c_k_g_r_o_u_n_d in a subshell.  The shell does  not
       wait  for the command to finish, and the return status is 0.  These are
       referred to as _a_s_y_n_c_h_r_o_n_o_u_s commands.  Commands separated by  a  ;;  are
       executed sequentially; the shell waits for each command to terminate in
       turn.   The  return  status is the exit status of the last command exe-
       cuted.

       AND and OR lists are sequences of one or more  pipelines  separated  by
       the  &&&&  and  |||| control operators, respectively.  AND and OR lists are
       executed with left associativity.  An AND list has the form

              _c_o_m_m_a_n_d_1 &&&& _c_o_m_m_a_n_d_2

       _c_o_m_m_a_n_d_2 is executed if, and only if, _c_o_m_m_a_n_d_1 returns an  exit  status
       of zero (success).

       An OR list has the form

              _c_o_m_m_a_n_d_1 |||| _c_o_m_m_a_n_d_2

       _c_o_m_m_a_n_d_2  is executed if, and only if, _c_o_m_m_a_n_d_1 returns a non-zero exit
       status.  The return status of AND and OR lists is the  exit  status  of
       the last command executed in the list.

   CCoommppoouunndd CCoommmmaannddss
       A  _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d is one of the following.  In most cases a _l_i_s_t in a
       command's description may be separated from the rest of the command  by
       one  or  more  newlines, and may be followed by a newline in place of a
       semicolon.

       (_l_i_s_t) _l_i_s_t is executed in a subshell (see CCOOMMMMAANNDD  EEXXEECCUUTTIIOONN  EENNVVIIRROONN--
              MMEENNTT  below for a description of a subshell environment).  Vari-
              able assignments and builtin commands that  affect  the  shell's
              environment do not remain in effect after the command completes.
              The return status is the exit status of _l_i_s_t.

       { _l_i_s_t; }
              _l_i_s_t is executed in the current shell environment.  _l_i_s_t must be
              terminated  with  a  newline  or  semicolon.  This is known as a
              _g_r_o_u_p _c_o_m_m_a_n_d.  The return status is the exit status of _l_i_s_t.

              Note that unlike the metacharacters (( and )), {{  and  }}  are  _r_e_-
              _s_e_r_v_e_d  _w_o_r_d_s  and must occur where a reserved word is permitted
              to be recognized.  Since they do not cause a  word  break,  they
              must  be  separated  from  _l_i_s_t  by  whitespace or another shell
              metacharacter.

       ((_e_x_p_r_e_s_s_i_o_n))
              The arithmetic _e_x_p_r_e_s_s_i_o_n is evaluated according  to  the  rules
              described  below  under  AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN.  If the value of
              the expression is non-zero, the return status  is  0;  otherwise
              the  return  status is 1.  The _e_x_p_r_e_s_s_i_o_n undergoes the same ex-
              pansions as if it were within double quotes, but unescaped  dou-
              ble quote characters in _e_x_p_r_e_s_s_i_o_n are not treated specially and
              are  removed.   Since  this  can  potentially  result  in  empty
              strings, this command treats those as expressions that  evaluate
              to 0.

       [[[[ _e_x_p_r_e_s_s_i_o_n ]]]]
              Evaluate the conditional expression _e_x_p_r_e_s_s_i_o_n and return a sta-
              tus  of  zero  (true) or non-zero (false).  Expressions are com-
              posed of the primaries described below under CCOONNDDIITTIIOONNAALL EEXXPPRREESS--
              SSIIOONNSS.  The words between the [[[[ and  ]]]]  do  not  undergo  word
              splitting  and pathname expansion.  The shell performs tilde ex-
              pansion, parameter and variable expansion, arithmetic expansion,
              command substitution, process substitution, and quote removal on
              those words.  Conditional operators such as --ff must be  unquoted
              to be recognized as primaries.

              When  used with [[[[, the << and >> operators sort lexicographically
              using the current locale.

              When the ==== and !!== operators are used, the string to  the  right
              of the operator is considered a pattern and matched according to
              the rules described below under PPaatttteerrnn MMaattcchhiinngg, as if the eexxtt--
              gglloobb shell option were enabled.  The == operator is equivalent to
              ====.   If  the  nnooccaasseemmaattcchh shell option is enabled, the match is
              performed without regard to the case of  alphabetic  characters.
              The  return  value  is  0 if the string matches (====) or does not
              match (!!==) the pattern, and 1 otherwise.  If  any  part  of  the
              pattern  is  quoted,  the quoted portion is matched as a string:
              every character in the quoted portion matches itself, instead of
              having any special pattern matching meaning.

              An additional binary operator, ==~~, is available, with  the  same
              precedence  as  ====  and  !!==.  When it is used, the string to the
              right of the operator is considered a POSIX extended regular ex-
              pression and matched accordingly (using the  POSIX  _r_e_g_c_o_m_p  and
              _r_e_g_e_x_e_c  interfaces  usually described in _r_e_g_e_x(3)).  The return
              value is 0 if the string matches the pattern, and  1  otherwise.
              If the regular expression is syntactically incorrect, the condi-
              tional expression's return value is 2.  If the nnooccaasseemmaattcchh shell
              option  is enabled, the match is performed without regard to the
              case of alphabetic characters.

              If any part of the pattern is  quoted,  the  quoted  portion  is
              matched  literally,  as  above.   If  the pattern is stored in a
              shell variable, quoting the variable expansion forces the entire
              pattern to be matched literally.  Treat bracket  expressions  in
              regular  expressions carefully, since normal quoting and pattern
              characters lose their meanings between brackets.

              The match succeeds if  the  pattern  matches  any  part  of  the
              string.  Anchor the pattern using the ^^ and $$ regular expression
              operators to force it to match the entire string.

              The  array  variable  BBAASSHH__RREEMMAATTCCHH  records  which  parts of the
              string matched the pattern.  The element  of  BBAASSHH__RREEMMAATTCCHH  with
              index  0  contains the portion of the string matching the entire
              regular expression.  Substrings matched by parenthesized  subex-
              pressions within the regular expression are saved in the remain-
              ing  BBAASSHH__RREEMMAATTCCHH indices.  The element of BBAASSHH__RREEMMAATTCCHH with in-
              dex _n is the portion of the string matching  the  _nth  parenthe-
              sized  subexpression.   BBaasshh  sets  BBAASSHH__RREEMMAATTCCHH  in  the global
              scope; declaring it as a local variable will lead to  unexpected
              results.

              Expressions  may  be  combined  using  the  following operators,
              listed in decreasing order of precedence:

              (( _e_x_p_r_e_s_s_i_o_n ))
                     Returns the value of _e_x_p_r_e_s_s_i_o_n.  This  may  be  used  to
                     override the normal precedence of operators.
              !! _e_x_p_r_e_s_s_i_o_n
                     True if _e_x_p_r_e_s_s_i_o_n is false.
              _e_x_p_r_e_s_s_i_o_n_1 &&&& _e_x_p_r_e_s_s_i_o_n_2
                     True if both _e_x_p_r_e_s_s_i_o_n_1 and _e_x_p_r_e_s_s_i_o_n_2 are true.
              _e_x_p_r_e_s_s_i_o_n_1 |||| _e_x_p_r_e_s_s_i_o_n_2
                     True if either _e_x_p_r_e_s_s_i_o_n_1 or _e_x_p_r_e_s_s_i_o_n_2 is true.

              The &&&& and |||| operators do not evaluate _e_x_p_r_e_s_s_i_o_n_2 if the value
              of  _e_x_p_r_e_s_s_i_o_n_1  is  sufficient to determine the return value of
              the entire conditional expression.

       ffoorr _n_a_m_e [ [ iinn _w_o_r_d _._._. ] ; ] ddoo _l_i_s_t ; ddoonnee
              First, expand The list of words following iinn, generating a  list
              of  items.   Then,  the  variable _n_a_m_e is set to each element of
              this list in turn, and _l_i_s_t is executed each time.   If  the  iinn
              _w_o_r_d is omitted, the ffoorr command executes _l_i_s_t once for each po-
              sitional  parameter that is set (see PPAARRAAMMEETTEERRSS below).  The re-
              turn status is the exit status of the  last  command  that  exe-
              cutes.  If the expansion of the items following iinn results in an
              empty  list,  no commands are executed, and the return status is
              0.

       ffoorr (( _e_x_p_r_1 ; _e_x_p_r_2 ; _e_x_p_r_3 )) [;] ddoo _l_i_s_t ; ddoonnee
              First, evaluate the arithmetic expression _e_x_p_r_1 according to the
              rules described below under AARRIITTHHMMEETTIICC  EEVVAALLUUAATTIIOONN.   Then,  re-
              peatedly evaluate the arithmetic expression _e_x_p_r_2 until it eval-
              uates  to  zero.  Each time _e_x_p_r_2 evaluates to a non-zero value,
              execute _l_i_s_t and evaluate the arithmetic expression  _e_x_p_r_3.   If
              any  expression  is omitted, it behaves as if it evaluates to 1.
              The return value is the exit status of the last command in  _l_i_s_t
              that  is  executed, or non-zero if any of the expressions is in-
              valid.

              Use the bbrreeaakk and ccoonnttiinnuuee builtins (see SSHHEELLLL BBUUIILLTTIINN  CCOOMMMMAANNDDSS
              below) to control loop execution.

       sseelleecctt _n_a_m_e [ iinn _w_o_r_d ] ; ddoo _l_i_s_t ; ddoonnee
              First,  expand the list of words following iinn, generating a list
              of items, and print the set of expanded words the  standard  er-
              ror,  each  preceded  by  a  number.  If the iinn _w_o_r_d is omitted,
              print the positional parameters (see PPAARRAAMMEETTEERRSS below).   sseelleecctt
              then  displays the PPSS33 prompt and reads a line from the standard
              input.  If the line consists of a number corresponding to one of
              the displayed words, then sseelleecctt sets the value of _n_a_m_e to  that
              word.   If  the  line  is  empty,  sseelleecctt displays the words and
              prompt again.  If EOF is read, sseelleecctt completes and  returns  1.
              Any  other  value  sets _n_a_m_e to null.  The line read is saved in
              the variable RREEPPLLYY.  The _l_i_s_t is executed after  each  selection
              until a bbrreeaakk command is executed.  The exit status of sseelleecctt is
              the exit status of the last command executed in _l_i_s_t, or zero if
              no commands were executed.

       ccaassee _w_o_r_d iinn [ [(] _p_a_t_t_e_r_n [ || _p_a_t_t_e_r_n ] ... ) _l_i_s_t ;; ] ... eessaacc
              A ccaassee command first expands _w_o_r_d, and tries to match it against
              each  _p_a_t_t_e_r_n  in turn, proceeding from first to last, using the
              matching rules described under PPaatttteerrnn MMaattcchhiinngg below.   A  pat-
              tern  list  is  a set of one or more patterns separated by , and
              the ) operator terminates the pattern list.   The  _w_o_r_d  is  ex-
              panded  using tilde expansion, parameter and variable expansion,
              arithmetic expansion, command substitution, process substitution
              and quote removal.  Each  _p_a_t_t_e_r_n  examined  is  expanded  using
              tilde  expansion,  parameter  and variable expansion, arithmetic
              expansion, command substitution, process substitution, and quote
              removal.  If the nnooccaasseemmaattcchh shell option is enabled, the  match
              is  performed  without  regard to the case of alphabetic charac-
              ters.  A _c_l_a_u_s_e is a pattern list and an associated _l_i_s_t.

              When a match is found, ccaassee executes the corresponding _l_i_s_t.  If
              the ;;;; operator terminates the case  clause,  the  ccaassee  command
              completes after the first match.  Using ;;&& in place of ;;;; causes
              execution  to  continue  with  the _l_i_s_t associated with the next
              pattern list.  Using ;;;;&& in place of ;;;; causes the shell to test
              the next pattern list in the statement, if any, and execute  any
              associated  _l_i_s_t  if  the  match  succeeds,  continuing the case
              statement execution as if the pattern list had not matched.  The
              exit status is zero if no pattern matches.

              Otherwise, it is the exit status of the last command executed in
              the last _l_i_s_t executed.

       iiff _l_i_s_t; tthheenn _l_i_s_t; [ eelliiff _l_i_s_t; tthheenn _l_i_s_t; ] ... [ eellssee _l_i_s_t; ] ffii
              The iiff _l_i_s_t is executed.  If its exit status is zero,  the  tthheenn
              _l_i_s_t  is  executed.   Otherwise,  each  eelliiff _l_i_s_t is executed in
              turn, and if its exit status is  zero,  the  corresponding  tthheenn
              _l_i_s_t is executed and the command completes.  Otherwise, the eellssee
              _l_i_s_t  is executed, if present.  The exit status is the exit sta-
              tus of the last command executed, or zero if no condition tested
              true.

       wwhhiillee _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee
       uunnttiill _l_i_s_t_-_1; ddoo _l_i_s_t_-_2; ddoonnee
              The wwhhiillee command continuously executes the list _l_i_s_t_-_2 as  long
              as the last command in the list _l_i_s_t_-_1 returns an exit status of
              zero.   The uunnttiill command is identical to the wwhhiillee command, ex-
              cept that the test is negated: _l_i_s_t_-_2 is executed as long as the
              last command in _l_i_s_t_-_1 returns a non-zero exit status.  The exit
              status of the wwhhiillee and uunnttiill commands is the exit status of the
              last command executed in _l_i_s_t_-_2, or zero if none was executed.

   CCoopprroocceesssseess
       A _c_o_p_r_o_c_e_s_s is a shell command preceded by the ccoopprroocc reserved word.  A
       coprocess is executed asynchronously in a subshell, as if  the  command
       had  been  terminated  with the && control operator, with a two-way pipe
       established between the executing shell and the coprocess.

       The syntax for a coprocess is:

              ccoopprroocc [_N_A_M_E] _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s]

       This creates a coprocess named _N_A_M_E.  _c_o_m_m_a_n_d may be  either  a  simple
       command  or  a  compound command (see above).  _N_A_M_E is a shell variable
       name.  If _N_A_M_E is not supplied, the default name is CCOOPPRROOCC.

       The recommended form to use for a coprocess is

              ccoopprroocc _N_A_M_E { _c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n_s]; }

       This form is preferred because simple commands result in the  coprocess
       always  being  named CCOOPPRROOCC, and it is simpler to use and more complete
       than the other compound commands.

       If _c_o_m_m_a_n_d is a compound command, _N_A_M_E is optional. The word  following
       ccoopprroocc  determines whether that word is interpreted as a variable name:
       it is interpreted as _N_A_M_E if it is not a reserved word that  introduces
       a  compound  command.   If _c_o_m_m_a_n_d is a simple command, _N_A_M_E is not al-
       lowed; this is to avoid confusion between _N_A_M_E and the  first  word  of
       the simple command.

       When  the  coprocess  is  executed, the shell creates an array variable
       (see AArrrraayyss below) named _N_A_M_E in the context of  the  executing  shell.
       The  standard  output  of _c_o_m_m_a_n_d is connected via a pipe to a file de-
       scriptor in the executing shell, and that file descriptor  is  assigned
       to _N_A_M_E[0].  The standard input of _c_o_m_m_a_n_d is connected via a pipe to a
       file descriptor in the executing shell, and that file descriptor is as-
       signed  to  _N_A_M_E[1].   This pipe is established before any redirections
       specified by the command (see RREEDDIIRREECCTTIIOONN below).  The file descriptors
       can be utilized as arguments to shell commands and  redirections  using
       standard  word expansions.  Other than those created to execute command
       and process substitutions, the file descriptors are  not  available  in
       subshells.

       The  process ID of the shell spawned to execute the coprocess is avail-
       able as the value of the variable _N_A_M_E_PID.  The wwaaiitt  builtin  may  be
       used to wait for the coprocess to terminate.

       Since  the  coprocess is created as an asynchronous command, the ccoopprroocc
       command always returns success.  The return status of  a  coprocess  is
       the exit status of _c_o_m_m_a_n_d.

   SShheellll FFuunnccttiioonn DDeeffiinniittiioonnss
       A  shell function is an object that is called like a simple command and
       executes a compound command with a new set  of  positional  parameters.
       Shell functions are declared as follows:

       _f_n_a_m_e () _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n]
       ffuunnccttiioonn _f_n_a_m_e [()] _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d [_r_e_d_i_r_e_c_t_i_o_n]
              This defines a function named _f_n_a_m_e.  The reserved word ffuunnccttiioonn
              is  optional.   If  the  ffuunnccttiioonn reserved word is supplied, the
              parentheses are optional.  The _b_o_d_y of the function is the  com-
              pound  command  _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d  (see CCoommppoouunndd CCoommmmaannddss above).
              That command is usually a _l_i_s_t of commands between { and },  but
              may be any command listed under CCoommppoouunndd CCoommmmaannddss above.  If the
              ffuunnccttiioonn reserved word is used, but the parentheses are not sup-
              plied, the braces are recommended.  _c_o_m_p_o_u_n_d_-_c_o_m_m_a_n_d is executed
              whenever  _f_n_a_m_e  is  specified  as the name of a simple command.
              When in posix mode, _f_n_a_m_e must be a valid shell _n_a_m_e and may not
              be the name of one of the POSIX _s_p_e_c_i_a_l  _b_u_i_l_t_i_n_s.   In  default
              mode,  a  function name can be any unquoted shell word that does
              not contain $$.

       Any redirections (see RREEDDIIRREECCTTIIOONN below) specified when a  function  is
       defined are performed when the function is executed.

       The  exit status of a function definition is zero unless a syntax error
       occurs or a readonly function with the same name already exists.   When
       executed,  the exit status of a function is the exit status of the last
       command executed in the body.  (See FFUUNNCCTTIIOONNSS below.)

CCOOMMMMEENNTTSS
       In a non-interactive shell, or an interactive shell in which the iinntteerr--
       aaccttiivvee__ccoommmmeennttss option to the  sshhoopptt  builtin  is  enabled  (see  SSHHEELLLL
       BBUUIILLTTIINN  CCOOMMMMAANNDDSS below), a word beginning with ## introduces a comment.
       A word begins at the beginning of a line, after unquoted whitespace, or
       after an operator.  The comment causes  that  word  and  all  remaining
       characters  on  that  line to be ignored.  An interactive shell without
       the iinntteerraaccttiivvee__ccoommmmeennttss option enabled does not allow  comments.   The
       iinntteerraaccttiivvee__ccoommmmeennttss  option  is  enabled  by  default  in  interactive
       shells.

QQUUOOTTIINNGG
       _Q_u_o_t_i_n_g is used to remove the special meaning of certain characters  or
       words  to  the shell.  Quoting can be used to disable special treatment
       for special characters, to prevent reserved words from being recognized
       as such, and to prevent parameter expansion.

       Each of the _m_e_t_a_c_h_a_r_a_c_t_e_r_s listed above under DDEEFFIINNIITTIIOONNSS  has  special
       meaning to the shell and must be quoted if it is to represent itself.

       When  the command history expansion facilities are being used (see HHIISS--
       TTOORRYY EEXXPPAANNSSIIOONN below), the _h_i_s_t_o_r_y _e_x_p_a_n_s_i_o_n character, usually !!, must
       be quoted to prevent history expansion.

       There are four quoting mechanisms: the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r, single quotes,
       double quotes, and dollar-single quotes.

       A non-quoted backslash (\\) is the _e_s_c_a_p_e _c_h_a_r_a_c_t_e_r.  It  preserves  the
       literal  value of the next character that follows, removing any special
       meaning it has, with the exception of <newline>.  If a \\<newline>  pair
       appears,  and  the  backslash  is  not itself quoted, the \\<newline> is
       treated as a line continuation (that is, it is removed from  the  input
       stream and effectively ignored).

       Enclosing  characters  in  single quotes preserves the literal value of
       each character within the quotes.  A single quote may not occur between
       single quotes, even when preceded by a backslash.

       Enclosing characters in double quotes preserves the  literal  value  of
       all  characters  within the quotes, with the exception of $$, ``, \\, and,
       when history expansion is enabled, !!.  When the shell is in posix mode,
       the !! has no special meaning within double quotes,  even  when  history
       expansion  is  enabled.   The  characters  $$ and `` retain their special
       meaning within double quotes.  The backslash retains its special  mean-
       ing  only when followed by one of the following characters: $$, ``, "", \\,
       or <<nneewwlliinnee>>.  Backslashes preceding characters without a special mean-
       ing are left unmodified.

       A double quote may be quoted within double quotes by preceding it  with
       a backslash.  If enabled, history expansion will be performed unless an
       !!   appearing in double quotes is escaped using a backslash.  The back-
       slash preceding the !!  is not removed.

       The special parameters ** and @@ have  special  meaning  when  in  double
       quotes (see PPAARRAAMMEETTEERRSS below).

       Character  sequences  of  the  form  $$'_s_t_r_i_n_g' are treated as a special
       variant of single quotes.  The sequence expands to _s_t_r_i_n_g,  with  back-
       slash-escaped  characters in _s_t_r_i_n_g replaced as specified by the ANSI C
       standard.  Backslash escape sequences, if present, are decoded as  fol-
       lows:
              \\aa     alert (bell)
              \\bb     backspace
              \\ee
              \\EE     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\''     single quote
              \\""     double quote
              \\??     question mark
              \\_n_n_n   The  eight-bit  character  whose value is the octal value
                     _n_n_n (one to three octal digits).
              \\xx_H_H   The eight-bit character whose value  is  the  hexadecimal
                     value _H_H (one or two hex digits).
              \\uu_H_H_H_H The  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value _H_H_H_H (one to four hex digits).
              \\UU_H_H_H_H_H_H_H_H
                     The Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits).
              \\cc_x    A control-_x character.

       The  expanded  result  is  single-quoted, as if the dollar sign had not
       been present.

   TTrraannssllaattiinngg SSttrriinnggss
       A double-quoted string preceded by a dollar sign ($$"_s_t_r_i_n_g") causes the
       string to be translated according to the current locale.   The  _g_e_t_t_e_x_t
       infrastructure  performs  the lookup and translation, using the LLCC__MMEESS--
       SSAAGGEESS, TTEEXXTTDDOOMMAAIINNDDIIRR, and TTEEXXTTDDOOMMAAIINN shell variables.  If  the  current
       locale is CC or PPOOSSIIXX, if there are no translations available, or if the
       string is not translated, the dollar sign is ignored, and the string is
       treated  as double-quoted as described above.  This is a form of double
       quoting, so the string remains double-quoted by default, whether or not
       it is translated and replaced.  If the nnooeexxppaanndd__ttrraannssllaattiioonn  option  is
       enabled  using  the sshhoopptt builtin, translated strings are single-quoted
       instead of double-quoted.  See the description  of  sshhoopptt  below  under
       SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS.

PPAARRAAMMEETTEERRSS
       A  _p_a_r_a_m_e_t_e_r is an entity that stores values.  It can be a _n_a_m_e, a num-
       ber, or one of the special characters listed below under SSppeecciiaall  PPaarraa--
       mmeetteerrss.  A _v_a_r_i_a_b_l_e is a parameter denoted by a _n_a_m_e.  A variable has a
       _v_a_l_u_e  and  zero or more _a_t_t_r_i_b_u_t_e_s.  Attributes are assigned using the
       ddeeccllaarree builtin command (see ddeeccllaarree below in SSHHEELLLL BBUUIILLTTIINN  CCOOMMMMAANNDDSS).
       The eexxppoorrtt and rreeaaddoonnllyy builtins assign specific attributes.

       A parameter is set if it has been assigned a value.  The null string is
       a  valid  value.  Once a variable is set, it may be unset only by using
       the uunnsseett builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       A _v_a_r_i_a_b_l_e is assigned to using a statement of the form

              _n_a_m_e=[_v_a_l_u_e]

       If _v_a_l_u_e is not given, the variable is assigned the null  string.   All
       _v_a_l_u_e_s  undergo tilde expansion, parameter and variable expansion, com-
       mand substitution, arithmetic expansion, and quote removal (see  EEXXPPAANN--
       SSIIOONN below).  If the variable has its iinntteeggeerr attribute set, then _v_a_l_u_e
       is evaluated as an arithmetic expression even if the $$((((...)))) expansion
       is not used (see AArriitthhmmeettiicc EExxppaannssiioonn below).  Word splitting and path-
       name  expansion  are not performed.  Assignment statements may also ap-
       pear as arguments to the aalliiaass, ddeeccllaarree, ttyyppeesseett, eexxppoorrtt, rreeaaddoonnllyy, and
       llooccaall builtin commands (_d_e_c_l_a_r_a_t_i_o_n commands).   When  in  posix  mode,
       these  builtins  may appear in a command after one or more instances of
       the ccoommmmaanndd builtin and retain these assignment statement properties.

       In the context where an assignment statement is assigning a value to  a
       shell  variable or array index, the "+=" operator appends to or adds to
       the variable's previous value.  This includes arguments to  _d_e_c_l_a_r_a_t_i_o_n
       commands  such as ddeeccllaarree that accept assignment statements.  When "+="
       is applied to a variable for which the iinntteeggeerr attribute has been  set,
       the variable's current value and _v_a_l_u_e are each evaluated as arithmetic
       expressions,  and  the sum of the results is assigned as the variable's
       value.  The current value is usually an integer constant, but may be an
       expression.  When "+=" is applied to an array variable  using  compound
       assignment (see AArrrraayyss below), the variable's value is not unset (as it
       is  when using "="), and new values are appended to the array beginning
       at one greater than the array's maximum index (for indexed  arrays)  or
       added  as additional key-value pairs in an associative array.  When ap-
       plied to a string-valued variable, _v_a_l_u_e is expanded  and  appended  to
       the variable's value.

       A variable can be assigned the _n_a_m_e_r_e_f attribute using the --nn option to
       the  ddeeccllaarree or llooccaall builtin commands (see the descriptions of ddeeccllaarree
       and llooccaall below) to create a _n_a_m_e_r_e_f, or a reference to  another  vari-
       able.   This  allows  variables to be manipulated indirectly.  Whenever
       the nameref variable is referenced, assigned to, unset, or has its  at-
       tributes  modified  (other than using or changing the _n_a_m_e_r_e_f attribute
       itself), the operation is actually performed on the variable  specified
       by  the  nameref  variable's  value.  A nameref is commonly used within
       shell functions to refer to a variable whose name is passed as an argu-
       ment to the function.  For instance, if a variable name is passed to  a
       shell function as its first argument, running

              declare -n ref=$1

       inside the function creates a local nameref variable rreeff whose value is
       the variable name passed as the first argument.  References and assign-
       ments to rreeff, and changes to its attributes, are treated as references,
       assignments, and attribute modifications to the variable whose name was
       passed  as  $$11.   If the control variable in a ffoorr loop has the nameref
       attribute, the list of words can be a list of shell  variables,  and  a
       name  reference is established for each word in the list, in turn, when
       the loop is executed.  Array variables cannot be given the nnaammeerreeff  at-
       tribute.   However, nameref variables can reference array variables and
       subscripted array variables.  Namerefs can be unset using the --nn option
       to the uunnsseett builtin.  Otherwise, if uunnsseett is executed with the name of
       a nameref variable as an  argument,  the  variable  referenced  by  the
       nameref variable is unset.

       When  the  shell  starts,  it reads its environment and creates a shell
       variable from each environment variable that has a valid name,  as  de-
       scribed below (see EENNVVIIRROONNMMEENNTT).

   PPoossiittiioonnaall PPaarraammeetteerrss
       A  _p_o_s_i_t_i_o_n_a_l  _p_a_r_a_m_e_t_e_r  is a parameter denoted by one or more digits,
       other than the single digit 0.  Positional parameters are assigned from
       the shell's arguments when it is invoked, and may be  reassigned  using
       the  sseett builtin command.  Positional parameters may not be assigned to
       with assignment statements.  The positional parameters are  temporarily
       replaced when a shell function is executed (see FFUUNNCCTTIIOONNSS below).

       When  a  positional parameter consisting of more than a single digit is
       expanded, it must be enclosed in braces (see EEXXPPAANNSSIIOONN below).  Without
       braces, a digit following $ can only refer to one of the first nine po-
       sitional parameters ($$11--$$99) or the special parameter $$00 (see  the  next
       section).

   SSppeecciiaall PPaarraammeetteerrss
       The  shell  treats  several parameters specially.  These parameters may
       only be referenced; assignment to them is not allowed.  Special parame-
       ters are denoted by one of the following characters.

       **      ($$**) Expands to the positional parameters,  starting  from  one.
              When  the expansion is not within double quotes, each positional
              parameter expands to a separate word.  In  contexts  where  word
              expansions  are  performed,  those  words are subject to further
              word splitting and pathname expansion.  When the  expansion  oc-
              curs  within double quotes, it expands to a single word with the
              value of each parameter separated by the first character of  the
              IIFFSS variable.  That is, ""$$**"" is equivalent to ""$$11_c$$22_c......"", where
              _c  is  the first character of the value of the IIFFSS variable.  If
              IIFFSS is unset, the parameters are separated by spaces.  If IIFFSS is
              null, the parameters are joined without intervening separators.
       @@      ($$@@) Expands to the positional parameters,  starting  from  one.
              In contexts where word splitting is performed, this expands each
              positional  parameter  to  a separate word; if not within double
              quotes, these words are subject to word splitting.  In  contexts
              where word splitting is not performed, such as the value portion
              of  an  assignment statement, this expands to a single word with
              each positional parameter separated by a space.  When the expan-
              sion occurs within double quotes, and  word  splitting  is  per-
              formed,  each  parameter  expands  to a separate word.  That is,
              ""$$@@"" is equivalent to ""$$11"" ""$$22"" ......  If the double-quoted expan-
              sion occurs within a word, the expansion of the first  parameter
              is joined with the expansion of the beginning part of the origi-
              nal word, and the expansion of the last parameter is joined with
              the expansion of the last part of the original word.  When there
              are  no  positional  parameters,  ""$$@@""  and $$@@ expand to nothing
              (i.e., they are removed).
       ##      ($$##) Expands to the number of positional parameters in decimal.
       ??      ($$??) Expands to the exit status of the  most  recently  executed
              command.
       --      ($$--) Expands to the current option flags as specified upon invo-
              cation,  by  the  sseett builtin command, or those set by the shell
              itself (such as the --ii option).
       $$      ($$$$) Expands to the process ID of the shell.  In a subshell,  it
              expands to the process ID of the parent shell, not the subshell.
       !!      ($$!!)Expands  to  the  process ID of the job most recently placed
              into the background, whether executed as an asynchronous command
              or using the bbgg builtin (see JJOOBB CCOONNTTRROOLL below).
       00      ($$00) Expands to the name of the shell or shell script.  This  is
              set  at shell initialization.  If bbaasshh is invoked with a file of
              commands, $$00 is set to the  name  of  that  file.   If  bbaasshh  is
              started with the --cc option, then $$00 is set to the first argument
              after  the string to be executed, if one is present.  Otherwise,
              it is set to the filename used to invoke bbaasshh, as given by argu-
              ment zero.

   SShheellll VVaarriiaabblleess
       The shell sets following variables:

       __      ($$__, an underscore) This has a number of meanings  depending  on
              context.  At shell startup, __ is set to the pathname used to in-
              voke  the  shell or shell script being executed as passed in the
              environment or argument list.  Subsequently, it expands  to  the
              last  argument  to  the  previous simple command executed in the
              foreground, after expansion.  It is also set to the  full  path-
              name  used to invoke each command executed and placed in the en-
              vironment exported to that command.  When checking mail, $$__  ex-
              pands to the name of the mail file currently being checked.
       BBAASSHH   Expands  to  the  full  filename used to invoke this instance of
              bbaasshh.
       BBAASSHHOOPPTTSS
              A colon-separated list of enabled shell options.  Each  word  in
              the  list  is  a  valid  argument for the --ss option to the sshhoopptt
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  The options
              appearing in BBAASSHHOOPPTTSS are those reported as  _o_n  by  sshhoopptt.   If
              this  variable  is  in  the environment when bbaasshh starts up, the
              shell enables each option in the list before reading any startup
              files.  If this variable is exported, child shells  will  enable
              each option in the list.  This variable is read-only.
       BBAASSHHPPIIDD
              Expands  to  the  process  ID of the current bbaasshh process.  This
              differs from $$$$ under certain circumstances, such  as  subshells
              that  do  not require bbaasshh to be re-initialized.  Assignments to
              BBAASSHHPPIIDD have no effect.  If BBAASSHHPPIIDD is unset, it loses its  spe-
              cial properties, even if it is subsequently reset.
       BBAASSHH__AALLIIAASSEESS
              An  associative  array  variable whose members correspond to the
              internal list of aliases as maintained  by  the  aalliiaass  builtin.
              Elements  added to this array appear in the alias list; however,
              unsetting array elements currently does not remove aliases  from
              the  alias list.  If BBAASSHH__AALLIIAASSEESS is unset, it loses its special
              properties, even if it is subsequently reset.
       BBAASSHH__AARRGGCC
              An array variable whose values are the number of  parameters  in
              each frame of the current bbaasshh execution call stack.  The number
              of  parameters  to  the  current  subroutine  (shell function or
              script executed with .. or ssoouurrccee) is at the top  of  the  stack.
              When  a  subroutine is executed, the number of parameters passed
              is pushed onto BBAASSHH__AARRGGCC.  The shell sets BBAASSHH__AARRGGCC only when in
              extended debugging mode (see the description of the eexxttddeebbuugg op-
              tion to the sshhoopptt builtin below).  Setting  eexxttddeebbuugg  after  the
              shell has started to execute a script, or referencing this vari-
              able  when  eexxttddeebbuugg is not set, may result in inconsistent val-
              ues.  Assignments to BBAASSHH__AARRGGCC have no effect, and it may not be
              unset.
       BBAASSHH__AARRGGVV
              An array variable containing all of the parameters in  the  cur-
              rent bbaasshh execution call stack.  The final parameter of the last
              subroutine  call is at the top of the stack; the first parameter
              of the initial call is at the bottom.  When a subroutine is exe-
              cuted, the shell pushes the supplied parameters onto  BBAASSHH__AARRGGVV.
              The  shell  sets  BBAASSHH__AARRGGVV only when in extended debugging mode
              (see the description of the eexxttddeebbuugg option to the sshhoopptt builtin
              below).  Setting eexxttddeebbuugg after the shell has started to execute
              a script, or referencing this variable when eexxttddeebbuugg is not set,
              may result in inconsistent  values.   Assignments  to  BBAASSHH__AARRGGVV
              have no effect, and it may not be unset.
       BBAASSHH__AARRGGVV00
              When  referenced, this variable expands to the name of the shell
              or shell script (identical to $$00; see the description of special
              parameter 0 above).  Assigning a value to BBAASSHH__AARRGGVV00 sets $$00  to
              the  same  value.   If BBAASSHH__AARRGGVV00 is unset, it loses its special
              properties, even if it is subsequently reset.
       BBAASSHH__CCMMDDSS
              An associative array variable whose members  correspond  to  the
              internal  hash  table  of  commands  as  maintained  by the hhaasshh
              builtin.  Adding elements to this array makes them appear in the
              hash table; however, unsetting array elements currently does not
              remove command names from the hash table.  If BBAASSHH__CCMMDDSS  is  un-
              set, it loses its special properties, even if it is subsequently
              reset.
       BBAASSHH__CCOOMMMMAANNDD
              Expands  to  the command currently being executed or about to be
              executed, unless the shell is executing a command as the  result
              of a trap, in which case it is the command executing at the time
              of  the  trap.   If  BBAASSHH__CCOOMMMMAANNDD is unset, it loses its special
              properties, even if it is subsequently reset.
       BBAASSHH__EEXXEECCUUTTIIOONN__SSTTRRIINNGG
              The command argument to the --cc invocation option.
       BBAASSHH__LLIINNEENNOO
              An array variable whose members are the line numbers  in  source
              files  where  each corresponding member of FFUUNNCCNNAAMMEE was invoked.
              $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}  is  the  line  number  in  the  source  file
              ($${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}})  where  $${{FFUUNNCCNNAAMMEE[[_$_i]]}}  was  called  (or
              $${{BBAASSHH__LLIINNEENNOO[[_$_i_-_1]]}} if referenced within  another  shell  func-
              tion).   Use  LLIINNEENNOO to obtain the current line number.  Assign-
              ments to BBAASSHH__LLIINNEENNOO have no effect, and it may not be unset.
       BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH
              A colon-separated list of directories in which the  eennaabbllee  com-
              mand looks for dynamically loadable builtins.
       BBAASSHH__MMOONNOOSSEECCOONNDDSS
              Each  time  this variable is referenced, it expands to the value
              returned by the system's monotonic clock, if one  is  available.
              If  there is no monotonic clock, this is equivalent to EEPPOOCCHHSSEECC--
              OONNDDSS.  If BBAASSHH__MMOONNOOSSEECCOONNDDSS is unset, it loses its special  prop-
              erties, even if it is subsequently reset.
       BBAASSHH__RREEMMAATTCCHH
              An  array  variable  whose members are assigned by the ==~~ binary
              operator to the [[[[ conditional command.  The element with  index
              0  is  the portion of the string matching the entire regular ex-
              pression.  The element with index _n is the portion of the string
              matching the _nth parenthesized subexpression.
       BBAASSHH__SSOOUURRCCEE
              An array variable whose members are the source  filenames  where
              the  corresponding  shell  function  names in the FFUUNNCCNNAAMMEE array
              variable are defined.  The shell function $${{FFUUNNCCNNAAMMEE[[_$_i]]}} is de-
              fined  in  the   file   $${{BBAASSHH__SSOOUURRCCEE[[_$_i]]}}   and   called   from
              $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}}.   Assignments  to  BBAASSHH__SSOOUURRCCEE have no ef-
              fect, and it may not be unset.
       BBAASSHH__SSUUBBSSHHEELLLL
              Incremented by one within each subshell or subshell  environment
              when  the  shell begins executing in that environment.  The ini-
              tial value is 0.  If BBAASSHH__SSUUBBSSHHEELLLL is unset, it loses  its  spe-
              cial properties, even if it is subsequently reset.
       BBAASSHH__TTRRAAPPSSIIGG
              Set  to the signal number corresponding to the trap action being
              executed during its execution.  See the description of ttrraapp  un-
              der  SSHHEELLLL  BBUUIILLTTIINN  CCOOMMMMAANNDDSS below for information about signal
              numbers and trap execution.
       BBAASSHH__VVEERRSSIINNFFOO
              A readonly array variable whose members hold version information
              for this instance of bbaasshh.  The values  assigned  to  the  array
              members are as follows:
              BBAASSHH__VVEERRSSIINNFFOO[[0]]        The major version number (the _r_e_l_e_a_s_e).
              BBAASSHH__VVEERRSSIINNFFOO[[1]]        The minor version number (the _v_e_r_s_i_o_n).
              BBAASSHH__VVEERRSSIINNFFOO[[2]]        The patch level.
              BBAASSHH__VVEERRSSIINNFFOO[[3]]        The build version.
              BBAASSHH__VVEERRSSIINNFFOO[[4]]        The release status (e.g., _b_e_t_a).
              BBAASSHH__VVEERRSSIINNFFOO[[5]]        The value of MMAACCHHTTYYPPEE.
       BBAASSHH__VVEERRSSIIOONN
              Expands  to  a string describing the version of this instance of
              bbaasshh (e.g., 5.2.37(3)-release).
       CCOOMMPP__CCWWOORRDD
              An index into $${{CCOOMMPP__WWOORRDDSS}} of the word containing  the  current
              cursor position.  This variable is available only in shell func-
              tions  invoked  by  the  programmable completion facilities (see
              PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__KKEEYY
              The key (or final key of a key sequence) used to invoke the cur-
              rent completion function.  This variable is  available  only  in
              shell  functions and external commands invoked by the programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__LLIINNEE
              The current command line.  This variable is  available  only  in
              shell  functions and external commands invoked by the programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__PPOOIINNTT
              The index of the current cursor position relative to the  begin-
              ning  of the current command.  If the current cursor position is
              at the end of the current command, the value of this variable is
              equal to $${{##CCOOMMPP__LLIINNEE}}.  This  variable  is  available  only  in
              shell  functions and external commands invoked by the programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__TTYYPPEE
              Set to an integer value corresponding to the type  of  attempted
              completion  that caused a completion function to be called: _T_A_B,
              for normal completion, _?, for listing completions after  succes-
              sive  tabs,  _!, for listing alternatives on partial word comple-
              tion, _@, to list completions if the word is not  unmodified,  or
              _%,  for  menu  completion.   This  variable is available only in
              shell functions and external commands invoked by the  programma-
              ble completion facilities (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOMMPP__WWOORRDDBBRREEAAKKSS
              The  set  of characters that the rreeaaddlliinnee library treats as word
              separators when performing word completion.  If  CCOOMMPP__WWOORRDDBBRREEAAKKSS
              is  unset, it loses its special properties, even if it is subse-
              quently reset.
       CCOOMMPP__WWOORRDDSS
              An array variable (see AArrrraayyss below) consisting of the  individ-
              ual  words  in the current command line.  The line is split into
              words as rreeaaddlliinnee would split it, using CCOOMMPP__WWOORRDDBBRREEAAKKSS  as  de-
              scribed  above.   This variable is available only in shell func-
              tions invoked by the  programmable  completion  facilities  (see
              PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).
       CCOOPPRROOCC An  array  variable  (see AArrrraayyss below) created to hold the file
              descriptors for output from and input to  an  unnamed  coprocess
              (see CCoopprroocceesssseess above).
       DDIIRRSSTTAACCKK
              An array variable (see AArrrraayyss below) containing the current con-
              tents  of  the directory stack.  Directories appear in the stack
              in the order they are displayed by the ddiirrss builtin.   Assigning
              to members of this array variable may be used to modify directo-
              ries  already in the stack, but the ppuusshhdd and ppooppdd builtins must
              be used to add and remove directories.  Assigning to this  vari-
              able  does not change the current directory.  If DDIIRRSSTTAACCKK is un-
              set, it loses its special properties, even if it is subsequently
              reset.
       EEPPOOCCHHRREEAALLTTIIMMEE
              Each time this parameter is referenced, it expands to the number
              of seconds since the Unix Epoch (see  _t_i_m_e(3))  as  a  floating-
              point  value  with  micro-second  granularity.   Assignments  to
              EEPPOOCCHHRREEAALLTTIIMMEE are ignored.  If EEPPOOCCHHRREEAALLTTIIMMEE is unset, it  loses
              its special properties, even if it is subsequently reset.
       EEPPOOCCHHSSEECCOONNDDSS
              Each time this parameter is referenced, it expands to the number
              of  seconds  since the Unix Epoch (see _t_i_m_e(3)).  Assignments to
              EEPPOOCCHHSSEECCOONNDDSS are ignored.  If EEPPOOCCHHSSEECCOONNDDSS is  unset,  it  loses
              its special properties, even if it is subsequently reset.
       EEUUIIDD   Expands  to  the effective user ID of the current user, initial-
              ized at shell startup.  This variable is readonly.
       FFUUNNCCNNAAMMEE
              An array variable containing the names of  all  shell  functions
              currently in the execution call stack.  The element with index 0
              is the name of any currently-executing shell function.  The bot-
              tom-most  element  (the  one  with the highest index) is "main".
              This variable exists only when a shell  function  is  executing.
              Assignments  to  FFUUNNCCNNAAMMEE have no effect.  If FFUUNNCCNNAAMMEE is unset,
              it loses its special properties, even if it is subsequently  re-
              set.

              This  variable  can  be  used  with BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE.
              Each  element  of  FFUUNNCCNNAAMMEE  has   corresponding   elements   in
              BBAASSHH__LLIINNEENNOO and BBAASSHH__SSOOUURRCCEE to describe the call stack.  For in-
              stance,    $${{FFUUNNCCNNAAMMEE[[_$_i]]}}    was    called    from   the   file
              $${{BBAASSHH__SSOOUURRCCEE[[_$_i_+_1]]}} at  line  number  $${{BBAASSHH__LLIINNEENNOO[[_$_i]]}}.   The
              ccaalllleerr builtin displays the current call stack using this infor-
              mation.
       GGRROOUUPPSS An  array  variable  containing  the list of groups of which the
              current user is a member.  Assignments to GGRROOUUPPSS have no effect.
              If GGRROOUUPPSS is unset, it loses its special properties, even if  it
              is subsequently reset.
       HHIISSTTCCMMDD
              The history number, or index in the history list, of the current
              command.   Assignments to HHIISSTTCCMMDD have no effect.  If HHIISSTTCCMMDD is
              unset, it loses its special properties, even  if  it  is  subse-
              quently reset.
       HHOOSSTTNNAAMMEE
              Automatically set to the name of the current host.
       HHOOSSTTTTYYPPEE
              Automatically  set  to a string that uniquely describes the type
              of machine on which bbaasshh is executing.  The default  is  system-
              dependent.
       LLIINNEENNOO Each  time this parameter is referenced, the shell substitutes a
              decimal number representing the current sequential  line  number
              (starting  with  1)  within a script or function.  When not in a
              script or function, the value substituted is not  guaranteed  to
              be meaningful.  If LLIINNEENNOO is unset, it loses its special proper-
              ties, even if it is subsequently reset.
       MMAACCHHTTYYPPEE
              Automatically  set  to  a string that fully describes the system
              type on which bbaasshh is executing, in the  standard  GNU  _c_p_u_-_c_o_m_-
              _p_a_n_y_-_s_y_s_t_e_m format.  The default is system-dependent.
       MMAAPPFFIILLEE
              An  array  variable  (see AArrrraayyss below) created to hold the text
              read by the mmaappffiillee builtin when no variable name is supplied.
       OOLLDDPPWWDD The previous working directory as set by the ccdd command.
       OOPPTTAARRGG The value of the last option argument processed by  the  ggeettooppttss
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       OOPPTTIINNDD The  index  of  the next argument to be processed by the ggeettooppttss
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       OOSSTTYYPPEE Automatically set to a string that describes the operating  sys-
              tem  on  which  bbaasshh is executing.  The default is system-depen-
              dent.
       PPIIPPEESSTTAATTUUSS
              An array variable (see AArrrraayyss below) containing a list  of  exit
              status  values  from  the commands in the most-recently-executed
              foreground pipeline, which may consist of only a simple  command
              (see SSHHEELLLL GGRRAAMMMMAARR above).  BBaasshh sets PPIIPPEESSTTAATTUUSS after executing
              multi-element  pipelines,  timed  and  negated pipelines, simple
              commands, subshells created with the ( operator, the [[[[  and  ((((
              compound commands, and after error conditions that result in the
              shell aborting command execution.
       PPPPIIDD   The  process  ID  of the shell's parent.  This variable is read-
              only.
       PPWWDD    The current working directory as set by the ccdd command.
       RRAANNDDOOMM Each time this parameter is referenced, it expands to  a  random
              integer  between  0 and 32767.  Assigning a value to RRAANNDDOOMM ini-
              tializes (seeds) the sequence of random  numbers.   Seeding  the
              random  number  generator  with the same constant value produces
              the same sequence of values.  If RRAANNDDOOMM is unset, it  loses  its
              special properties, even if it is subsequently reset.
       RREEAADDLLIINNEE__AARRGGUUMMEENNTT
              Any  numeric  argument  given to a rreeaaddlliinnee command that was de-
              fined using "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) when it
              was invoked.
       RREEAADDLLIINNEE__LLIINNEE
              The contents of the rreeaaddlliinnee line buffer, for use with "bind -x"
              (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       RREEAADDLLIINNEE__MMAARRKK
              The position of the mark (saved insertion point) in the rreeaaddlliinnee
              line buffer, for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN  CCOOMMMMAANNDDSS
              below).  The characters between the insertion point and the mark
              are often called the _r_e_g_i_o_n.
       RREEAADDLLIINNEE__PPOOIINNTT
              The position of the insertion point in the rreeaaddlliinnee line buffer,
              for use with "bind -x" (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
       RREEPPLLYY  Set  to  the line of input read by the rreeaadd builtin command when
              no arguments are supplied.
       SSEECCOONNDDSS
              Each time this parameter is referenced, it expands to the number
              of seconds since shell invocation.  If a value  is  assigned  to
              SSEECCOONNDDSS,  the  value  returned upon subsequent references is the
              number of seconds since the assignment plus the value  assigned.
              The  number  of seconds at shell invocation and the current time
              are always determined by querying the system clock at one-second
              resolution.  If SSEECCOONNDDSS is unset, it loses its  special  proper-
              ties, even if it is subsequently reset.
       SSHHEELLLLOOPPTTSS
              A  colon-separated  list of enabled shell options.  Each word in
              the list is a valid argument  for  the  --oo  option  to  the  sseett
              builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  The options
              appearing  in  SSHHEELLLLOOPPTTSS are those reported as _o_n by sseett --oo.  If
              this variable is in the environment when  bbaasshh  starts  up,  the
              shell enables each option in the list before reading any startup
              files.   If  this variable is exported, child shells will enable
              each option in the list.  This variable is read-only.
       SSHHLLVVLL  Incremented by one each time an instance of bbaasshh is started.
       SSRRAANNDDOOMM
              Each time it is referenced, this variable expands  to  a  32-bit
              pseudo-random number.  The random number generator is not linear
              on  systems  that support _/_d_e_v_/_u_r_a_n_d_o_m or _a_r_c_4_r_a_n_d_o_m(3), so each
              returned number has no relationship to the numbers preceding it.
              The random number generator cannot be seeded, so assignments  to
              this variable have no effect.  If SSRRAANNDDOOMM is unset, it loses its
              special properties, even if it is subsequently reset.
       UUIIDD    Expands to the user ID of the current user, initialized at shell
              startup.  This variable is readonly.

       The  shell  uses the following variables. In some cases, bbaasshh assigns a
       default value to a variable; these cases are noted below.

       BBAASSHH__CCOOMMPPAATT
              The value is used to set the shell's compatibility  level.   See
              SSHHEELLLL  CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below for a description of the various
              compatibility levels and their effects.  The value may be a dec-
              imal number (e.g., 4.2) or an integer (e.g.,  42)  corresponding
              to  the desired compatibility level.  If BBAASSHH__CCOOMMPPAATT is unset or
              set to the empty string, the compatibility level is set  to  the
              default  for  the  current  version.  If BBAASSHH__CCOOMMPPAATT is set to a
              value that is not one of the  valid  compatibility  levels,  the
              shell  prints  an error message and sets the compatibility level
              to the default for the current version.  A subset of  the  valid
              values  correspond  to  the compatibility levels described below
              under SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE.  For example,  4.2  and  42  are
              valid  values  that  correspond to the ccoommppaatt4422 sshhoopptt option and
              set the compatibility level to 42.  The current version is  also
              a valid value.
       BBAASSHH__EENNVV
              If  this parameter is set when bbaasshh is executing a shell script,
              its expanded value is interpreted as a filename containing  com-
              mands  to initialize the shell before it reads and executes com-
              mands from the script.  The value of BBAASSHH__EENNVV  is  subjected  to
              parameter expansion, command substitution, and arithmetic expan-
              sion  before  being interpreted as a filename.  PPAATTHH is not used
              to search for the resultant filename.
       BBAASSHH__XXTTRRAACCEEFFDD
              If set to an integer corresponding to a valid  file  descriptor,
              bbaasshh  writes the trace output generated when "set -x" is enabled
              to that file descriptor, instead of  the  standard  error.   The
              file  descriptor  is  closed  when BBAASSHH__XXTTRRAACCEEFFDD is unset or as-
              signed a new value.  Unsetting BBAASSHH__XXTTRRAACCEEFFDD or assigning it the
              empty string causes the trace output to be sent to the  standard
              error.  Note that setting BBAASSHH__XXTTRRAACCEEFFDD to 2 (the standard error
              file  descriptor) and then unsetting it will result in the stan-
              dard error being closed.
       CCDDPPAATTHH The search path for the ccdd command.  This is  a  colon-separated
              list of directories where the shell looks for directories speci-
              fied  as  arguments  to  the  ccdd  command.   A  sample  value is
              ".:~:/usr".
       CCHHIILLDD__MMAAXX
              Set the number of exited child status values for  the  shell  to
              remember.   BBaasshh will not allow this value to be decreased below
              a POSIX-mandated minimum, and there is  a  maximum  value  (cur-
              rently  8192)  that  this  may not exceed.  The minimum value is
              system-dependent.
       CCOOLLUUMMNNSS
              Used by the sseelleecctt compound command to  determine  the  terminal
              width  when  printing selection lists.  Automatically set if the
              cchheecckkwwiinnssiizzee option is enabled or in an interactive  shell  upon
              receipt of a SSIIGGWWIINNCCHH.
       CCOOMMPPRREEPPLLYY
              An array variable from which bbaasshh reads the possible completions
              generated  by  a shell function invoked by the programmable com-
              pletion facility (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn below).  Each  ar-
              ray element contains one possible completion.
       EEMMAACCSS  If  bbaasshh  finds  this variable in the environment when the shell
              starts with value "t", it assumes that the shell is  running  in
              an Emacs shell buffer and disables line editing.
       EENNVV    Expanded  and  executed  similarly  to  BBAASSHH__EENNVV (see IINNVVOOCCAATTIIOONN
              above) when an interactive shell is invoked in posix mode.
       EEXXEECCIIGGNNOORREE
              A colon-separated list of shell patterns (see PPaatttteerrnn  MMaattcchhiinngg)
              defining  the  set  of filenames to be ignored by command search
              using PPAATTHH.  Files whose full pathnames match one of these  pat-
              terns  are  not  considered executable files for the purposes of
              completion and command execution via PPAATTHH lookup.  This does not
              affect the behavior of the [[, tteesstt, and [[[[ commands.  Full path-
              names in the command hash table are not subject  to  EEXXEECCIIGGNNOORREE.
              Use  this  variable to ignore shared library files that have the
              executable bit set, but are not executable files.   The  pattern
              matching honors the setting of the eexxttgglloobb shell option.
       FFCCEEDDIITT The default editor for the ffcc builtin command.
       FFIIGGNNOORREE
              A  colon-separated  list  of  suffixes to ignore when performing
              filename completion (see RREEAADDLLIINNEE below).  A filename whose suf-
              fix matches one of the entries in FFIIGGNNOORREE is excluded  from  the
              list of matched filenames.  A sample value is ".o:~".
       FFUUNNCCNNEESSTT
              If  set  to  a  numeric  value greater than 0, defines a maximum
              function nesting level.  Function invocations that  exceed  this
              nesting level cause the current command to abort.
       GGLLOOBBIIGGNNOORREE
              A  colon-separated  list  of  patterns  defining the set of file
              names to be ignored by  pathname  expansion.   If  a  file  name
              matched  by a pathname expansion pattern also matches one of the
              patterns in GGLLOOBBIIGGNNOORREE, it is removed from the list of  matches.
              The pattern matching honors the setting of the eexxttgglloobb shell op-
              tion.
       GGLLOOBBSSOORRTT
              Controls  how the results of pathname expansion are sorted.  The
              value of this variable specifies the sort criteria and sort  or-
              der  for the results of pathname expansion.  If this variable is
              unset or set to the null string,  pathname  expansion  uses  the
              historical  behavior  of  sorting  by name, in ascending lexico-
              graphic order as determined by the LLCC__CCOOLLLLAATTEE shell variable.

              If set, a valid value begins with an optional _+,  which  is  ig-
              nored, or _-, which reverses the sort order from ascending to de-
              scending,  followed  by a sort specifier.  The valid sort speci-
              fiers are _n_a_m_e, _n_u_m_e_r_i_c, _s_i_z_e, _m_t_i_m_e, _a_t_i_m_e, _c_t_i_m_e, and  _b_l_o_c_k_s,
              which sort the files on name, names in numeric rather than lexi-
              cographic  order, file size, modification time, access time, in-
              ode change time, and number of blocks, respectively.  If any  of
              the  non-name  keys compare as equal (e.g., if two files are the
              same size), sorting uses the name as a secondary sort key.

              For example, a value of _-_m_t_i_m_e sorts the results  in  descending
              order by modification time (newest first).

              The  _n_u_m_e_r_i_c  specifier treats names consisting solely of digits
              as numbers and sorts them using  their  numeric  value  (so  "2"
              sorts before "10", for example).  When using _n_u_m_e_r_i_c, names con-
              taining  non-digits  sort  after all the all-digit names and are
              sorted by name using the traditional behavior.

              A sort specifier of _n_o_s_o_r_t disables sorting completely; bbaasshh re-
              turns the results in the order they are read from the file  sys-
              tem, ignoring any leading _-.

              If  the  sort  specifier  is  missing, it defaults to _n_a_m_e, so a
              value of _+ is equivalent to the null string, and a  value  of  _-
              sorts  by  name in descending order.  Any invalid value restores
              the historical sorting behavior.
       HHIISSTTCCOONNTTRROOLL
              A colon-separated list of values controlling  how  commands  are
              saved  on  the  history  list.   If  the list of values includes
              _i_g_n_o_r_e_s_p_a_c_e, lines which begin with a ssppaaccee  character  are  not
              saved  in  the history list.  A value of _i_g_n_o_r_e_d_u_p_s causes lines
              matching the previous history entry not to be saved.  A value of
              _i_g_n_o_r_e_b_o_t_h is shorthand for _i_g_n_o_r_e_s_p_a_c_e and _i_g_n_o_r_e_d_u_p_s.  A value
              of _e_r_a_s_e_d_u_p_s causes all previous lines matching the current line
              to be removed from the history list before that line  is  saved.
              Any  value  not in the above list is ignored.  If HHIISSTTCCOONNTTRROOLL is
              unset, or does not include a valid value, bbaasshh saves  all  lines
              read  by  the  shell  parser on the history list, subject to the
              value of HHIISSTTIIGGNNOORREE.  If the first line of a multi-line compound
              command was saved, the  second  and  subsequent  lines  are  not
              tested,  and are added to the history regardless of the value of
              HHIISSTTCCOONNTTRROOLL.  If the first line was not saved,  the  second  and
              subsequent lines of the command are not saved either.
       HHIISSTTFFIILLEE
              The name of the file in which command history is saved (see HHIISS--
              TTOORRYY  below).   BBaasshh assigns a default value of _~_/_._b_a_s_h___h_i_s_t_o_r_y.
              If HHIISSTTFFIILLEE is unset or null, the shell does not save  the  com-
              mand history when it exits.
       HHIISSTTFFIILLEESSIIZZEE
              The maximum number of lines contained in the history file.  When
              this  variable  is  assigned  a value, the history file is trun-
              cated, if necessary, to contain no more than the number of  his-
              tory entries that total no more than that number of lines by re-
              moving  the oldest entries.  If the history list contains multi-
              line entries, the history file may contain more lines than  this
              maximum  to  avoid leaving partial history entries.  The history
              file is also truncated to this size  after  writing  it  when  a
              shell  exits  or by the hhiissttoorryy builtin.  If the value is 0, the
              history file is truncated to zero size.  Non-numeric values  and
              numeric  values  less  than  zero inhibit truncation.  The shell
              sets the default value to the value of  HHIISSTTSSIIZZEE  after  reading
              any startup files.
       HHIISSTTIIGGNNOORREE
              A  colon-separated list of patterns used to decide which command
              lines should be saved on the history list.  If  a  command  line
              matches  one  of  the patterns in the value of HHIISSTTIIGGNNOORREE, it is
              not saved on the history list.  Each pattern is anchored at  the
              beginning  of  the  line  and must match the complete line (bbaasshh
              does not  implicitly append a  "**").   Each  pattern  is  tested
              against  the  line after the checks specified by HHIISSTTCCOONNTTRROOLL are
              applied.  In addition to the normal shell pattern matching char-
              acters, "&&" matches the previous history line.  A backslash  es-
              capes  the  "&&";  the  backslash  is removed before attempting a
              match.  If the first line of a multi-line compound  command  was
              saved,  the  second and subsequent lines are not tested, and are
              added to the history regardless of the value of HHIISSTTIIGGNNOORREE.   If
              the first line was not saved, the second and subsequent lines of
              the  command  are not saved either.  The pattern matching honors
              the setting of the eexxttgglloobb shell option.
              HHIISSTTIIGGNNOORREE subsumes some of the function of HHIISSTTCCOONNTTRROOLL.  A pat-
              tern of "&" is identical to "ignoredups", and a  pattern  of  "[
              ]*"  is  identical  to  "ignorespace".  Combining these two pat-
              terns, separating them with a colon, provides the  functionality
              of "ignoreboth".
       HHIISSTTSSIIZZEE
              The  number  of commands to remember in the command history (see
              HHIISSTTOORRYY below).  If the value is 0, commands are  not  saved  in
              the history list.  Numeric values less than zero result in every
              command  being  saved  on  the history list (there is no limit).
              The shell sets the  default  value  to  500  after  reading  any
              startup files.
       HHIISSTTTTIIMMEEFFOORRMMAATT
              If  this  variable  is  set and not null, its value is used as a
              format string for _s_t_r_f_t_i_m_e(3) to print the time stamp associated
              with each history entry displayed by the  hhiissttoorryy  builtin.   If
              this  variable  is set, the shell writes time stamps to the his-
              tory file so they may be preserved across shell sessions.   This
              uses  the  history  comment  character to distinguish timestamps
              from other history lines.
       HHOOMMEE   The home directory of the current user; the default argument for
              the ccdd builtin command.  The value of this variable is also used
              when performing tilde expansion.
       HHOOSSTTFFIILLEE
              Contains the name of a file in the  same  format  as  _/_e_t_c_/_h_o_s_t_s
              that should be read when the shell needs to complete a hostname.
              The  list  of possible hostname completions may be changed while
              the shell is running; the next time hostname completion  is  at-
              tempted  after  the  value is changed, bbaasshh adds the contents of
              the new file to the existing list.  If HHOOSSTTFFIILLEE is set, but  has
              no  value,  or  does  not name a readable file, bbaasshh attempts to
              read _/_e_t_c_/_h_o_s_t_s to obtain the list of possible hostname  comple-
              tions.  When HHOOSSTTFFIILLEE is unset, bbaasshh clears the hostname list.
       IIFFSS    The _I_n_t_e_r_n_a_l _F_i_e_l_d _S_e_p_a_r_a_t_o_r that is used for word splitting af-
              ter  expansion  and  to  split  lines  into  words with the rreeaadd
              builtin command.  Word splitting is described below under EEXXPPAANN--
              SSIIOONN.  The default value is "<space><tab><newline>".
       IIGGNNOORREEEEOOFF
              Controls the action of an interactive shell on receipt of an EEOOFF
              character as the sole input.  If set, the value is the number of
              consecutive EEOOFF characters which must  be  typed  as  the  first
              characters  on an input line before bbaasshh exits.  If the variable
              is set but does not have a numeric value, or the value is  null,
              the  default value is 10.  If it is unset, EEOOFF signifies the end
              of input to the shell.
       IINNPPUUTTRRCC
              The filename for the rreeaaddlliinnee startup file, overriding  the  de-
              fault of _~_/_._i_n_p_u_t_r_c (see RREEAADDLLIINNEE below).
       IINNSSIIDDEE__EEMMAACCSS
              If  this  variable  appears  in  the  environment when the shell
              starts, bbaasshh assumes that it is running inside  an  Emacs  shell
              buffer  and  may disable line editing, depending on the value of
              TTEERRMM.
       LLAANNGG   Used to determine the  locale  category  for  any  category  not
              specifically selected with a variable starting with LLCC__.
       LLCC__AALLLL This  variable  overrides  the  value  of LLAANNGG and any other LLCC__
              variable specifying a locale category.
       LLCC__CCOOLLLLAATTEE
              This variable determines the collation order used  when  sorting
              the  results  of pathname expansion, and determines the behavior
              of range expressions, equivalence  classes,  and  collating  se-
              quences within pathname expansion and pattern matching.
       LLCC__CCTTYYPPEE
              This  variable  determines  the interpretation of characters and
              the behavior of character classes within pathname expansion  and
              pattern matching.
       LLCC__MMEESSSSAAGGEESS
              This  variable  determines  the locale used to translate double-
              quoted strings preceded by a $$.
       LLCC__NNUUMMEERRIICC
              This variable determines the locale  category  used  for  number
              formatting.
       LLCC__TTIIMMEE
              This  variable  determines the locale category used for data and
              time formatting.
       LLIINNEESS  Used by the sseelleecctt compound  command  to  determine  the  column
              length  for  printing selection lists.  Automatically set if the
              cchheecckkwwiinnssiizzee option is enabled or in an interactive  shell  upon
              receipt of a SSIIGGWWIINNCCHH.
       MMAAIILL   If the value is set to a file or directory name and the MMAAIILLPPAATTHH
              variable  is  not  set,  bbaasshh informs the user of the arrival of
              mail in the specified file or Maildir-format directory.
       MMAAIILLCCHHEECCKK
              Specifies how often (in seconds) bbaasshh checks for mail.  The  de-
              fault  is  60  seconds.   When it is time to check for mail, the
              shell does so before displaying the  primary  prompt.   If  this
              variable  is  unset,  or  set  to  a  value that is not a number
              greater than or equal to zero, the shell disables mail checking.
       MMAAIILLPPAATTHH
              A colon-separated list of filenames to be checked for mail.  The
              message to be printed when mail arrives in a particular file may
              be specified by separating the filename from the message with  a
              "?".   When  used  in the text of the message, $$__ expands to the
              name of the current mailfile.  For example:
              MMAAIILLPPAATTHH='/var/mail/bfox?"You have mail":~/shell-mail?"$_ has mail!"'
              BBaasshh can be configured to supply a default value for this  vari-
              able  (there  is  no  value by default), but the location of the
              user  mail  files  that  it  uses  is  system  dependent  (e.g.,
              /var/mail/$$UUSSEERR).
       OOPPTTEERRRR If set to the value 1, bbaasshh displays error messages generated by
              the  ggeettooppttss builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
              OOPPTTEERRRR is initialized to 1 each time the shell is invoked  or  a
              shell script is executed.
       PPAATTHH   The  search  path for commands.  It is a colon-separated list of
              directories in which the shell looks for commands  (see  CCOOMMMMAANNDD
              EEXXEECCUUTTIIOONN  below).   A  zero-length (null) directory name in the
              value of PPAATTHH indicates the current directory.  A null directory
              name may appear as two adjacent colons,  or  as  an  initial  or
              trailing  colon.   The  default path is system-dependent, and is
              set by the administrator who installs bbaasshh.  A common value is
                   /usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin
       PPOOSSIIXXLLYY__CCOORRRREECCTT
              If this variable is in the environment  when  bbaasshh  starts,  the
              shell  enters posix mode before reading the startup files, as if
              the ----ppoossiixx invocation option had been supplied.  If it  is  set
              while  the  shell is running, bbaasshh enables posix mode, as if the
              command "set -o posix" had been executed.  When the shell enters
              posix mode, it sets this variable if it was not already set.
       PPRROOMMPPTT__CCOOMMMMAANNDD
              If this variable is set, and is an array, the value of each  set
              element  is  executed as a command prior to issuing each primary
              prompt.  If this is set but not an array variable, its value  is
              used as a command to execute instead.
       PPRROOMMPPTT__DDIIRRTTRRIIMM
              If  set  to a number greater than zero, the value is used as the
              number of trailing directory components to retain when expanding
              the \\ww and \\WW  prompt  string  escapes  (see  PPRROOMMPPTTIINNGG  below).
              Characters removed are replaced with an ellipsis.
       PPSS00    The  value  of  this parameter is expanded (see PPRROOMMPPTTIINNGG below)
              and displayed by interactive shells after reading a command  and
              before the command is executed.
       PPSS11    The  value  of  this parameter is expanded (see PPRROOMMPPTTIINNGG below)
              and used as the primary prompt string.   The  default  value  is
              "\s-\v\$ ".
       PPSS22    The  value of this parameter is expanded as with PPSS11 and used as
              the secondary prompt string.  The default is "> ".
       PPSS33    The value of this parameter is used as the prompt for the sseelleecctt
              command (see SSHHEELLLL GGRRAAMMMMAARR above).
       PPSS44    The value of this parameter is expanded  as  with  PPSS11  and  the
              value is printed before each command bbaasshh displays during an ex-
              ecution trace.  The first character of the expanded value of PPSS44
              is replicated multiple times, as necessary, to indicate multiple
              levels of indirection.  The default is "+ ".
       SSHHEELLLL  This  variable expands to the full pathname to the shell.  If it
              is not set when the shell starts, bbaasshh assigns to  it  the  full
              pathname of the current user's login shell.
       TTIIMMEEFFOORRMMAATT
              The  value of this parameter is used as a format string specify-
              ing how the timing information for pipelines prefixed  with  the
              ttiimmee  reserved word should be displayed.  The %% character intro-
              duces an escape sequence that is expanded to  a  time  value  or
              other  information.  The escape sequences and their meanings are
              as follows; the brackets denote optional portions.
              %%%%        A literal %%.
              %%[[_p]][[ll]]RR  The elapsed time in seconds.
              %%[[_p]][[ll]]UU  The number of CPU seconds spent in user mode.
              %%[[_p]][[ll]]SS  The number of CPU seconds spent in system mode.
              %%PP        The CPU percentage, computed as (%U + %S) / %R.

              The optional _p is a digit specifying the _p_r_e_c_i_s_i_o_n,  the  number
              of fractional digits after a decimal point.  A value of 0 causes
              no  decimal point or fraction to be output.  ttiimmee prints at most
              six digits after the decimal point; values of _p greater  than  6
              are changed to 6.  If _p is not specified, ttiimmee prints three dig-
              its after the decimal point.

              The  optional ll specifies a longer format, including minutes, of
              the form _M_Mm_S_S._F_Fs.  The value of _p determines  whether  or  not
              the fraction is included.

              If  this  variable  is not set, bbaasshh acts as if it had the value
              $$''\\nnrreeaall\\tt%%33llRR\\nnuusseerr\\tt%%33llUU\\nnssyyss\\tt%%33llSS''.  If the value  is  null,
              bbaasshh  does  not display any timing information.  A trailing new-
              line is added when the format string is displayed.
       TTMMOOUUTT  If set to a value greater than zero, the rreeaadd builtin  uses  the
              value  as its default timeout.  The sseelleecctt command terminates if
              input does not arrive after TTMMOOUUTT seconds when input  is  coming
              from  a  terminal.  In an interactive shell, the value is inter-
              preted as the number of seconds to wait for a line of input  af-
              ter  issuing  the primary prompt.  BBaasshh terminates after waiting
              for that number of seconds if a complete line of input does  not
              arrive.
       TTMMPPDDIIRR If  set, bbaasshh uses its value as the name of a directory in which
              bbaasshh creates temporary files for the shell's use.
       aauuttoo__rreessuummee
              This variable controls how the shell interacts with the user and
              job control.  If this variable is set, simple commands  consist-
              ing  of only a single word, without redirections, are treated as
              candidates for resumption of an existing stopped job.  There  is
              no  ambiguity  allowed;  if there is more than one job beginning
              with or containing the word, this selects the most recently  ac-
              cessed  job.  The _n_a_m_e of a stopped job, in this context, is the
              command line used to start it, as displayed by jjoobbss.  If set  to
              the  value  _e_x_a_c_t, the word must match the name of a stopped job
              exactly; if set to _s_u_b_s_t_r_i_n_g, the word needs  to  match  a  sub-
              string  of  the name of a stopped job.  The _s_u_b_s_t_r_i_n_g value pro-
              vides functionality analogous to the %%??  job identifier (see JJOOBB
              CCOONNTTRROOLL below).  If set to any other value (e.g.,  _p_r_e_f_i_x),  the
              word  must  be  a  prefix of a stopped job's name; this provides
              functionality analogous to the %%_s_t_r_i_n_g job identifier.
       hhiissttcchhaarrss
              The two or three characters  which  control  history  expansion,
              quick  substitution, and tokenization (see HHIISSTTOORRYY EEXXPPAANNSSIIOONN be-
              low).  The first character is the _h_i_s_t_o_r_y  _e_x_p_a_n_s_i_o_n  character,
              the  character  which  begins a history expansion, normally "!!".
              The second character is the _q_u_i_c_k _s_u_b_s_t_i_t_u_t_i_o_n  character,  nor-
              mally  "^^".  When it appears as the first character on the line,
              history substitution repeats the previous command, replacing one
              string with another.  The optional third character is  the  _h_i_s_-
              _t_o_r_y  _c_o_m_m_e_n_t character,  normally "##", which indicates that the
              remainder of the line is a comment when it appears as the  first
              character  of  a  word.   The history comment character disables
              history substitution for the remaining words on  the  line.   It
              does not necessarily cause the shell parser to treat the rest of
              the line as a comment.

   AArrrraayyss
       BBaasshh  provides one-dimensional indexed and associative array variables.
       Any variable may be used as an indexed array; the ddeeccllaarree  builtin  ex-
       plicitly  declares  an array.  There is no maximum limit on the size of
       an array, nor any requirement that members be indexed or assigned  con-
       tiguously.   Indexed arrays are referenced using arithmetic expressions
       that must expand to an integer (see AARRIITTHHMMEETTIICC  EEVVAALLUUAATTIIOONN  below)  and
       are  zero-based;  associative  arrays  are  referenced  using arbitrary
       strings.  Unless otherwise noted, indexed array indices  must  be  non-
       negative integers.

       The  shell performs parameter and variable expansion, arithmetic expan-
       sion, command substitution, and quote removal  on  indexed  array  sub-
       scripts.  Since this can potentially result in empty strings, subscript
       indexing treats those as expressions that evaluate to 0.

       The  shell  performs tilde expansion, parameter and variable expansion,
       arithmetic expansion, command substitution, and quote removal on  asso-
       ciative  array subscripts.  Empty strings cannot be used as associative
       array keys.

       BBaasshh automatically creates an indexed array if any variable is assigned
       to using the syntax
              _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e .
       The _s_u_b_s_c_r_i_p_t is treated as an arithmetic expression that must evaluate
       to a number greater than or equal to zero.  To  explicitly  declare  an
       indexed array, use
              ddeeccllaarree --aa _n_a_m_e
       (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).
              ddeeccllaarree --aa _n_a_m_e[_s_u_b_s_c_r_i_p_t]
       is also accepted; the _s_u_b_s_c_r_i_p_t is ignored.

       Associative arrays are created using
              ddeeccllaarree --AA _n_a_m_e
       .

       Attributes may be specified for an array variable using the ddeeccllaarree and
       rreeaaddoonnllyy builtins.  Each attribute applies to all members of an array.

       Arrays are assigned using compound assignments of the form _n_a_m_e=((value_1
       ...  value_n)),  where  each _v_a_l_u_e may be of the form [_s_u_b_s_c_r_i_p_t]=_s_t_r_i_n_g.
       Indexed array assignments do not require  anything  but  _s_t_r_i_n_g.   Each
       _v_a_l_u_e  in the list is expanded using the shell expansions described be-
       low under EEXXPPAANNSSIIOONN, but _v_a_l_u_es that are valid variable assignments in-
       cluding the brackets and subscript do not undergo brace  expansion  and
       word splitting, as with individual variable assignments.

       When  assigning  to  indexed  arrays, if the optional brackets and sub-
       script are supplied, that index is assigned to; otherwise the index  of
       the  element  assigned  is  the last index assigned to by the statement
       plus one.  Indexing starts at zero.

       When assigning to an associative array, the words in a compound assign-
       ment may be either assignment statements, for which  the  subscript  is
       required,  or  a list of words that is interpreted as a sequence of al-
       ternating keys and values: _n_a_m_e=(( _k_e_y_1 _v_a_l_u_e_1 _k_e_y_2 _v_a_l_u_e_2 ...)).   These
       are  treated  identically  to  _n_a_m_e=(( [_k_e_y_1]=_v_a_l_u_e_1 [_k_e_y_2]=_v_a_l_u_e_2 ...)).
       The first word in the list determines how the remaining words  are  in-
       terpreted;  all  assignments  in a list must be of the same type.  When
       using key/value pairs, the keys may not be missing or  empty;  a  final
       missing value is treated like the empty string.

       This  syntax is also accepted by the ddeeccllaarree builtin.  Individual array
       elements may be assigned to using the _n_a_m_e[_s_u_b_s_c_r_i_p_t]=_v_a_l_u_e syntax  in-
       troduced above.

       When  assigning  to an indexed array, if _n_a_m_e is subscripted by a nega-
       tive number, that number is interpreted as relative to one greater than
       the maximum index of _n_a_m_e, so negative indices count back from the  end
       of the array, and an index of -1 references the last element.

       The "+=" operator appends to an array variable when assigning using the
       compound assignment syntax; see PPAARRAAMMEETTEERRSS above.

       An  array  element  is referenced using ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}.  The braces
       are required to avoid conflicts with pathname expansion.  If  _s_u_b_s_c_r_i_p_t
       is @@ or **, the word expands to all members of _n_a_m_e, unless noted in the
       description  of  a  builtin or word expansion.  These subscripts differ
       only when the word appears within double quotes.  If the word  is  dou-
       ble-quoted,  ${_n_a_m_e[*]} expands to a single word with the value of each
       array member separated by the first character of the IIFFSS special  vari-
       able,  and  ${_n_a_m_e[@]} expands each element of _n_a_m_e to a separate word.
       When there are no array members, ${_n_a_m_e[@]} expands to nothing.  If the
       double-quoted expansion occurs within a  word,  the  expansion  of  the
       first  parameter  is joined with the beginning part of the expansion of
       the original word, and the expansion of the last  parameter  is  joined
       with  the  last  part  of  the expansion of the original word.  This is
       analogous to the expansion of the special parameters ** and @@ (see  SSppee--
       cciiaall PPaarraammeetteerrss above).

       ${#_n_a_m_e[_s_u_b_s_c_r_i_p_t]}  expands  to  the length of ${_n_a_m_e[_s_u_b_s_c_r_i_p_t]}.  If
       _s_u_b_s_c_r_i_p_t is ** or @@, the expansion is the number of elements in the ar-
       ray.

       If the _s_u_b_s_c_r_i_p_t used to reference an element of an indexed array eval-
       uates to a number less than zero, it is interpreted as relative to  one
       greater  than the maximum index of the array, so negative indices count
       back from the end of the array, and an index of -1 references the  last
       element.

       Referencing an array variable without a subscript is equivalent to ref-
       erencing  the array with a subscript of 0.  Any reference to a variable
       using a valid subscript is valid; bbaasshh creates an array if necessary.

       An array variable is considered set if a subscript has been assigned  a
       value.  The null string is a valid value.

       It  is possible to obtain the keys (indices) of an array as well as the
       values.  ${!!_n_a_m_e[_@]} and ${!!_n_a_m_e[_*]} expand to the indices assigned  in
       array variable _n_a_m_e.  The treatment when in double quotes is similar to
       the expansion of the special parameters _@ and _* within double quotes.

       The uunnsseett builtin is used to destroy arrays.  uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t] un-
       sets  the  array element at index _s_u_b_s_c_r_i_p_t, for both indexed and asso-
       ciative arrays.  Negative subscripts to indexed arrays are  interpreted
       as  described  above.   Unsetting the last element of an array variable
       does not unset the variable.  uunnsseett _n_a_m_e, where _n_a_m_e is an  array,  re-
       moves  the entire array.  uunnsseett _n_a_m_e[_s_u_b_s_c_r_i_p_t] behaves differently de-
       pending on whether _n_a_m_e is an indexed or associative  array  when  _s_u_b_-
       _s_c_r_i_p_t is ** or @@.  If _n_a_m_e is an associative array, this unsets the el-
       ement  with  subscript  ** or @@.  If _n_a_m_e is an indexed array, unset re-
       moves all of the elements but does not remove the array itself.

       When using a variable name with a subscript as an argument  to  a  com-
       mand,  such  as with uunnsseett, without using the word expansion syntax de-
       scribed above, (e.g., unset a[4]), the argument is subject to  pathname
       expansion.   Quote  the  argument  if pathname expansion is not desired
       (e.g., unset 'a[4]').

       The ddeeccllaarree, llooccaall, and rreeaaddoonnllyy builtins each accept a  --aa  option  to
       specify  an indexed array and a --AA option to specify an associative ar-
       ray.  If both options are supplied,  --AA  takes  precedence.   The  rreeaadd
       builtin  accepts  a  --aa  option to assign a list of words read from the
       standard input to an array.  The sseett and ddeeccllaarree builtins display array
       values in a way that allows them to be reused  as  assignments.   Other
       builtins  accept  array name arguments as well (e.g., mmaappffiillee); see the
       descriptions of individual builtins below for details.  The shell  pro-
       vides a number of builtin array variables.

EEXXPPAANNSSIIOONN
       Expansion is performed on the command line after it has been split into
       words.  The shell performs these expansions: _b_r_a_c_e _e_x_p_a_n_s_i_o_n, _t_i_l_d_e _e_x_-
       _p_a_n_s_i_o_n, _p_a_r_a_m_e_t_e_r _a_n_d _v_a_r_i_a_b_l_e _e_x_p_a_n_s_i_o_n, _c_o_m_m_a_n_d _s_u_b_s_t_i_t_u_t_i_o_n, _a_r_i_t_h_-
       _m_e_t_i_c _e_x_p_a_n_s_i_o_n, _w_o_r_d _s_p_l_i_t_t_i_n_g, _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n, and _q_u_o_t_e _r_e_m_o_v_a_l.

       The order of expansions is: brace expansion; tilde expansion, parameter
       and  variable expansion, arithmetic expansion, and command substitution
       (done in a left-to-right fashion); word splitting; pathname  expansion;
       and quote removal.

       On systems that can support it, there is an additional expansion avail-
       able:  _p_r_o_c_e_s_s  _s_u_b_s_t_i_t_u_t_i_o_n.   This  is  performed at the same time as
       tilde, parameter, variable, and arithmetic expansion and  command  sub-
       stitution.

       _Q_u_o_t_e  _r_e_m_o_v_a_l  is  always performed last.  It removes quote characters
       present in the original word, not ones resulting from one of the  other
       expansions, unless they have been quoted themselves.

       Only  brace  expansion,  word splitting, and pathname expansion can in-
       crease the number of words of the expansion; other expansions expand  a
       single  word to a single word.  The only exceptions to this are the ex-
       pansions  of  ""$$@@""  and  ""$${{_n_a_m_e[[@@]]}}"",  and,  in  most  cases,  $$**  and
       $${{_n_a_m_e[[**]]}} as explained above (see PPAARRAAMMEETTEERRSS).

   BBrraaccee EExxppaannssiioonn
       _B_r_a_c_e  _e_x_p_a_n_s_i_o_n is a mechanism to generate arbitrary strings sharing a
       common prefix and suffix, either of which can be empty.  This mechanism
       is similar to _p_a_t_h_n_a_m_e _e_x_p_a_n_s_i_o_n, but the filenames generated need  not
       exist.   Patterns to be brace expanded are formed from an optional _p_r_e_-
       _a_m_b_l_e, followed by either a series of comma-separated strings or a  se-
       quence  expression  between  a  pair of braces, followed by an optional
       _p_o_s_t_s_c_r_i_p_t.  The preamble is prefixed to each string  contained  within
       the  braces,  and  the  postscript  is  then appended to each resulting
       string, expanding left to right.

       Brace expansions may be nested.  The results of  each  expanded  string
       are not sorted; brace expansion preserves left to right order.  For ex-
       ample, a{{d,c,b}}e expands into "ade ace abe".

       A  sequence  expression  takes the form _x...._y[[...._i_n_c_r]], where _x and _y are
       either integers or single letters, and _i_n_c_r, an optional increment,  is
       an integer.  When integers are supplied, the expression expands to each
       number  between  _x  and  _y,  inclusive.  If either _x or _y begins with a
       zero, each generated term will contain the same number of digits, zero-
       padding where necessary.  When letters are supplied, the expression ex-
       pands to each character lexicographically between _x and  _y,  inclusive,
       using  the  C  locale.  Note that both _x and _y must be of the same type
       (integer or letter).  When the increment is supplied, it is used as the
       difference between each term.  The default increment is 1 or -1 as  ap-
       propriate.

       Brace expansion is performed before any other expansions, and any char-
       acters  special to other expansions are preserved in the result.  It is
       strictly textual.  BBaasshh does not apply any syntactic interpretation  to
       the context of the expansion or the text between the braces.

       A  correctly-formed  brace  expansion must contain unquoted opening and
       closing braces, and at least one unquoted comma or a valid sequence ex-
       pression.  Any incorrectly formed brace expansion is left unchanged.

       A "{" or Q , may be quoted with a backslash to prevent its  being  con-
       sidered  part of a brace expression.  To avoid conflicts with parameter
       expansion, the string "${" is not considered eligible for brace  expan-
       sion, and inhibits brace expansion until the closing "}".

       This construct is typically used as shorthand when the common prefix of
       the strings to be generated is longer than in the above example:

              mkdir /usr/local/src/bash/{old,new,dist,bugs}
       or
              chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}

       Brace  expansion  introduces  a  slight incompatibility with historical
       versions of sshh.  sshh does not treat opening or closing braces  specially
       when  they  appear as part of a word, and preserves them in the output.
       BBaasshh removes braces from words as a  consequence  of  brace  expansion.
       For example, a word entered to sshh as "file{1,2}" appears identically in
       the output.  BBaasshh outputs that word as "file1 file2" after brace expan-
       sion.   Start  bbaasshh  with the ++BB option or disable brace expansion with
       the ++BB option to the sseett command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) for
       strict sshh compatibility.

   TTiillddee EExxppaannssiioonn
       If a word begins with an unquoted tilde character  ("~~"),  all  of  the
       characters  preceding  the  first unquoted slash (or all characters, if
       there is no unquoted slash) are considered a _t_i_l_d_e_-_p_r_e_f_i_x.  If none  of
       the  characters  in  the tilde-prefix are quoted, the characters in the
       tilde-prefix following the tilde are treated as a possible _l_o_g_i_n  _n_a_m_e.
       If  this  login name is the null string, the tilde is replaced with the
       value of the shell parameter HHOOMMEE.  If HHOOMMEE is unset, the tilde expands
       to the home directory of the user executing the shell instead.   Other-
       wise,  the  tilde-prefix is replaced with the home directory associated
       with the specified login name.

       If the tilde-prefix is a "~+", the value of the shell variable PPWWDD  re-
       places the tilde-prefix.  If the tilde-prefix is a "~-", the shell sub-
       stitutes  the value of the shell variable OOLLDDPPWWDD, if it is set.  If the
       characters following the tilde in the tilde-prefix consist of a  number
       _N,  optionally prefixed by a "+" or a "-", the tilde-prefix is replaced
       with the corresponding element from the directory stack, as it would be
       displayed by the ddiirrss builtin invoked with the characters following the
       tilde in the tilde-prefix as an argument.  If the characters  following
       the tilde in the tilde-prefix consist of a number without a leading "+"
       or "-", tilde expansion assumes "+".

       The  results  of tilde expansion are treated as if they were quoted, so
       the replacement is not subject to word splitting  and  pathname  expan-
       sion.

       If  the login name is invalid, or the tilde expansion fails, the tilde-
       prefix is unchanged.

       BBaasshh checks each variable assignment for unquoted tilde-prefixes  imme-
       diately  following  a :: or the first ==, and performs tilde expansion in
       these cases.  Consequently, one may use filenames with  tildes  in  as-
       signments  to PPAATTHH, MMAAIILLPPAATTHH, and CCDDPPAATTHH, and the shell assigns the ex-
       panded value.

       BBaasshh also performs tilde expansion on words satisfying  the  conditions
       of variable assignments (as described above under PPAARRAAMMEETTEERRSS) when they
       appear  as arguments to simple commands.  BBaasshh does not do this, except
       for the _d_e_c_l_a_r_a_t_i_o_n commands listed above, when in posix mode.

   PPaarraammeetteerr EExxppaannssiioonn
       The "$$" character introduces parameter expansion, command substitution,
       or arithmetic expansion.  The parameter name or symbol to  be  expanded
       may  be enclosed in braces, which are optional but serve to protect the
       variable to be expanded from characters immediately following it  which
       could be interpreted as part of the name.

       When  braces  are  used, the matching ending brace is the first "}}" not
       escaped by a backslash or within a quoted string, and not within an em-
       bedded arithmetic expansion, command substitution, or parameter  expan-
       sion.

       The basic form of parameter expansion is

       ${_p_a_r_a_m_e_t_e_r}

       which substitutes the value of _p_a_r_a_m_e_t_e_r.  The braces are required when
       _p_a_r_a_m_e_t_e_r  is  a positional parameter with more than one digit, or when
       _p_a_r_a_m_e_t_e_r is followed by a character which is not to be interpreted  as
       part  of  its  name.   The  _p_a_r_a_m_e_t_e_r is a shell parameter as described
       above PPAARRAAMMEETTEERRSS) or an array reference (AArrrraayyss).

       If the first character of _p_a_r_a_m_e_t_e_r is an exclamation  point  (!!),  and
       _p_a_r_a_m_e_t_e_r is not a _n_a_m_e_r_e_f, it introduces a level of indirection.  BBaasshh
       uses the value formed by expanding the rest of _p_a_r_a_m_e_t_e_r as the new _p_a_-
       _r_a_m_e_t_e_r;  this new parameter is then expanded and that value is used in
       the rest of the expansion, rather than the expansion  of  the  original
       _p_a_r_a_m_e_t_e_r.   This is known as _i_n_d_i_r_e_c_t _e_x_p_a_n_s_i_o_n.  The value is subject
       to tilde expansion,  parameter  expansion,  command  substitution,  and
       arithmetic  expansion.   If _p_a_r_a_m_e_t_e_r is a nameref, this expands to the
       name of the parameter referenced by _p_a_r_a_m_e_t_e_r instead of performing the
       complete indirect expansion, for compatibility.  The exceptions to this
       are the expansions of ${!!_p_r_e_f_i_x**} and ${!!_n_a_m_e[_@]} described below.  The
       exclamation point must immediately follow the left brace  in  order  to
       introduce indirection.

       In each of the cases below, _w_o_r_d is subject to tilde expansion, parame-
       ter expansion, command substitution, and arithmetic expansion.

       When not performing substring expansion, using the forms documented be-
       low  (e.g.,  ::--),  bbaasshh  tests  for  a parameter that is unset or null.
       Omitting the colon tests only for a parameter that is unset.

       ${_p_a_r_a_m_e_t_e_r::--_w_o_r_d}
              UUssee DDeeffaauulltt VVaalluueess.  If _p_a_r_a_m_e_t_e_r is unset or null,  the  expan-
              sion  of _w_o_r_d is substituted.  Otherwise, the value of _p_a_r_a_m_e_t_e_r
              is substituted.

       ${_p_a_r_a_m_e_t_e_r::==_w_o_r_d}
              AAssssiiggnn DDeeffaauulltt VVaalluueess.  If _p_a_r_a_m_e_t_e_r is unset or null,  the  ex-
              pansion  of  _w_o_r_d is assigned to _p_a_r_a_m_e_t_e_r, and the expansion is
              the final value of _p_a_r_a_m_e_t_e_r.  Positional parameters and special
              parameters may not be assigned in this way.

       ${_p_a_r_a_m_e_t_e_r::??_w_o_r_d}
              DDiissppllaayy EErrrroorr iiff NNuullll oorr UUnnsseett.  If _p_a_r_a_m_e_t_e_r is null or  unset,
              the shell writes the expansion of _w_o_r_d (or a message to that ef-
              fect if _w_o_r_d is not present) to the standard error and, if it is
              not  interactive,  exits with a non-zero status.  An interactive
              shell does not exit, but does not execute the command associated
              with the expansion.  Otherwise, the value of _p_a_r_a_m_e_t_e_r  is  sub-
              stituted.

       ${_p_a_r_a_m_e_t_e_r::++_w_o_r_d}
              UUssee  AAlltteerrnnaattee VVaalluuee.  If _p_a_r_a_m_e_t_e_r is null or unset, nothing is
              substituted, otherwise the expansion  of  _w_o_r_d  is  substituted.
              The value of _p_a_r_a_m_e_t_e_r is not used.

       ${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t}
       ${_p_a_r_a_m_e_t_e_r::_o_f_f_s_e_t::_l_e_n_g_t_h}
              SSuubbssttrriinngg  EExxppaannssiioonn.  Expands to up to _l_e_n_g_t_h characters of the
              value of _p_a_r_a_m_e_t_e_r starting at the character specified  by  _o_f_f_-
              _s_e_t.   If _p_a_r_a_m_e_t_e_r is @@ or **, an indexed array subscripted by @@
              or **, or an associative array name, the results  differ  as  de-
              scribed  below.   If  ::_l_e_n_g_t_h is omitted (the first form above),
              this expands to the substring of the value of _p_a_r_a_m_e_t_e_r starting
              at the character specified by _o_f_f_s_e_t and extending to the end of
              the value.  If _o_f_f_s_e_t is omitted, it is treated as 0.  If _l_e_n_g_t_h
              is omitted, but the colon after _o_f_f_s_e_t is present, it is treated
              as 0.  _l_e_n_g_t_h and _o_f_f_s_e_t are arithmetic expressions (see  AARRIITTHH--
              MMEETTIICC EEVVAALLUUAATTIIOONN below).

              If  _o_f_f_s_e_t  evaluates  to  a number less than zero, the value is
              used as an offset in characters from the end of the value of _p_a_-
              _r_a_m_e_t_e_r.  If _l_e_n_g_t_h evaluates to a number less than zero, it  is
              interpreted as an offset in characters from the end of the value
              of  _p_a_r_a_m_e_t_e_r rather than a number of characters, and the expan-
              sion is the characters between _o_f_f_s_e_t  and  that  result.   Note
              that  a  negative  offset must be separated from the colon by at
              least one space to avoid being confused with the ::-- expansion.

              If _p_a_r_a_m_e_t_e_r is @@ or **, the result is _l_e_n_g_t_h positional  parame-
              ters  beginning  at _o_f_f_s_e_t.  A negative _o_f_f_s_e_t is taken relative
              to one greater than the greatest  positional  parameter,  so  an
              offset of -1 evaluates to the last positional parameter (or 0 if
              there  are  no positional parameters).  It is an expansion error
              if _l_e_n_g_t_h evaluates to a number less than zero.

              If _p_a_r_a_m_e_t_e_r is an indexed array name subscripted by @ or *, the
              result is the _l_e_n_g_t_h members of the array beginning with ${_p_a_r_a_-
              _m_e_t_e_r[_o_f_f_s_e_t]}.  A negative _o_f_f_s_e_t  is  taken  relative  to  one
              greater than the maximum index of the specified array.  It is an
              expansion error if _l_e_n_g_t_h evaluates to a number less than zero.

              Substring expansion applied to an associative array produces un-
              defined results.

              Substring  indexing  is zero-based unless the positional parame-
              ters are used, in which case the indexing starts  at  1  by  de-
              fault.   If _o_f_f_s_e_t is 0, and the positional parameters are used,
              $$00 is prefixed to the list.

       ${!!_p_r_e_f_i_x**}
       ${!!_p_r_e_f_i_x@@}
              NNaammeess mmaattcchhiinngg pprreeffiixx.  Expands to the names of variables  whose
              names begin with _p_r_e_f_i_x, separated by the first character of the
              IIFFSS  special variable.  When _@ is used and the expansion appears
              within double quotes, each variable name expands to  a  separate
              word.

       ${!!_n_a_m_e[_@]}
       ${!!_n_a_m_e[_*]}
              LLiisstt  ooff  aarrrraayy  kkeeyyss.  If _n_a_m_e is an array variable, expands to
              the list of array indices (keys) assigned in _n_a_m_e.  If  _n_a_m_e  is
              not  an  array,  expands to 0 if _n_a_m_e is set and null otherwise.
              When _@ is used and the expansion appears within  double  quotes,
              each key expands to a separate word.

       ${##_p_a_r_a_m_e_t_e_r}
              PPaarraammeetteerr  lleennggtthh.   Substitutes the length in characters of the
              expanded value of _p_a_r_a_m_e_t_e_r.  If _p_a_r_a_m_e_t_e_r is ** or @@, the  value
              substituted  is the number of positional parameters.  If _p_a_r_a_m_e_-
              _t_e_r is an array name subscripted by ** or @@,  the  value  substi-
              tuted  is  the number of elements in the array.  If _p_a_r_a_m_e_t_e_r is
              an indexed array name subscripted by  a  negative  number,  that
              number  is interpreted as relative to one greater than the maxi-
              mum index of _p_a_r_a_m_e_t_e_r, so negative indices count back from  the
              end  of  the  array, and an index of -1 references the last ele-
              ment.

       ${_p_a_r_a_m_e_t_e_r##_w_o_r_d}
       ${_p_a_r_a_m_e_t_e_r####_w_o_r_d}
              RReemmoovvee mmaattcchhiinngg pprreeffiixx ppaatttteerrnn.  The _w_o_r_d is expanded to produce
              a pattern just as in pathname expansion, and matched against the
              expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
              tteerrnn MMaattcchhiinngg below.  If the pattern matches  the  beginning  of
              the  value of _p_a_r_a_m_e_t_e_r, then the result of the expansion is the
              expanded value of _p_a_r_a_m_e_t_e_r with the shortest  matching  pattern
              (the  "#"  case) or the longest matching pattern (the "##" case)
              deleted.  If _p_a_r_a_m_e_t_e_r is @@ or **, the pattern removal  operation
              is  applied to each positional parameter in turn, and the expan-
              sion is the resultant list.  If _p_a_r_a_m_e_t_e_r is an  array  variable
              subscripted  with  @@  or **, the pattern removal operation is ap-
              plied to each member of the array in turn, and the expansion  is
              the resultant list.

       ${_p_a_r_a_m_e_t_e_r%%_w_o_r_d}
       ${_p_a_r_a_m_e_t_e_r%%%%_w_o_r_d}
              RReemmoovvee mmaattcchhiinngg ssuuffffiixx ppaatttteerrnn.  The _w_o_r_d is expanded to produce
              a pattern just as in pathname expansion, and matched against the
              expanded value of _p_a_r_a_m_e_t_e_r using the rules described under PPaatt--
              tteerrnn  MMaattcchhiinngg below.  If the pattern matches a trailing portion
              of the expanded value of _p_a_r_a_m_e_t_e_r, then the result of  the  ex-
              pansion  is  the  expanded  value of _p_a_r_a_m_e_t_e_r with the shortest
              matching pattern (the "%" case) or the longest matching  pattern
              (the  "%%"  case)  deleted.  If _p_a_r_a_m_e_t_e_r is @@ or **, the pattern
              removal operation is applied to  each  positional  parameter  in
              turn,  and the expansion is the resultant list.  If _p_a_r_a_m_e_t_e_r is
              an array variable subscripted with @@ or **, the  pattern  removal
              operation  is  applied  to each member of the array in turn, and
              the expansion is the resultant list.

       ${_p_a_r_a_m_e_t_e_r//_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r////_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r//##_p_a_t_t_e_r_n//_s_t_r_i_n_g}
       ${_p_a_r_a_m_e_t_e_r//%%_p_a_t_t_e_r_n//_s_t_r_i_n_g}
              PPaatttteerrnn ssuubbssttiittuuttiioonn.  The _p_a_t_t_e_r_n is expanded to produce a pat-
              tern and matched against the expanded value of _p_a_r_a_m_e_t_e_r as  de-
              scribed under PPaatttteerrnn MMaattcchhiinngg below.  The longest match of _p_a_t_-
              _t_e_r_n  in the expanded value is replaced with _s_t_r_i_n_g.  _s_t_r_i_n_g un-
              dergoes  tilde  expansion,  parameter  and  variable  expansion,
              arithmetic  expansion,  command  and  process  substitution, and
              quote removal.

              In the first form above, only the first match is  replaced.   If
              there are two slashes separating _p_a_r_a_m_e_t_e_r and _p_a_t_t_e_r_n (the sec-
              ond  form  above),  all  matches  of  _p_a_t_t_e_r_n  are replaced with
              _s_t_r_i_n_g.  If _p_a_t_t_e_r_n is preceded by ## (the third form above),  it
              must  match at the beginning of the expanded value of _p_a_r_a_m_e_t_e_r.
              If _p_a_t_t_e_r_n is preceded by %% (the fourth  form  above),  it  must
              match at the end of the expanded value of _p_a_r_a_m_e_t_e_r.

              If  the  expansion  of  _s_t_r_i_n_g  is  null, matches of _p_a_t_t_e_r_n are
              deleted and the // following _p_a_t_t_e_r_n may be omitted.

              If the ppaattssuubb__rreeppllaacceemmeenntt shell option is enabled  using  sshhoopptt,
              any  unquoted  instances  of  &&  in _s_t_r_i_n_g are replaced with the
              matching portion of _p_a_t_t_e_r_n.

              Quoting any part of _s_t_r_i_n_g inhibits replacement in the expansion
              of the quoted portion, including replacement strings  stored  in
              shell  variables.   Backslash escapes && in _s_t_r_i_n_g; the backslash
              is removed in order to permit a literal  &&  in  the  replacement
              string.   Backslash  can  also be used to escape a backslash; \\\\
              results in a literal backslash in the replacement.  Users should
              take care if _s_t_r_i_n_g is double-quoted to avoid unwanted  interac-
              tions  between the backslash and double-quoting, since backslash
              has special meaning within double quotes.  Pattern  substitution
              performs  the check for unquoted && after expanding _s_t_r_i_n_g; shell
              programmers should quote any occurrences of && they  want  to  be
              taken literally in the replacement and ensure any instances of &&
              they want to be replaced are unquoted.

              Like  the  pattern  removal operators, double quotes surrounding
              the replacement string quote the expanded characters, while dou-
              ble quotes enclosing the entire parameter substitution  do  not,
              since  the expansion is performed in a context that doesn't take
              any enclosing double quotes into account.

              If the nnooccaasseemmaattcchh shell option is enabled, the  match  is  per-
              formed without regard to the case of alphabetic characters.

              If _p_a_r_a_m_e_t_e_r is @@ or **, the substitution operation is applied to
              each  positional parameter in turn, and the expansion is the re-
              sultant list.  If _p_a_r_a_m_e_t_e_r is  an  array  variable  subscripted
              with  @@ or **, the substitution operation is applied to each mem-
              ber of the array in turn, and the  expansion  is  the  resultant
              list.

       ${_p_a_r_a_m_e_t_e_r^^_p_a_t_t_e_r_n}
       ${_p_a_r_a_m_e_t_e_r^^^^_p_a_t_t_e_r_n}
       ${_p_a_r_a_m_e_t_e_r,,_p_a_t_t_e_r_n}
       ${_p_a_r_a_m_e_t_e_r,,,,_p_a_t_t_e_r_n}
              CCaassee  mmooddiiffiiccaattiioonn.   This expansion modifies the case of alpha-
              betic characters in _p_a_r_a_m_e_t_e_r.  First, the _p_a_t_t_e_r_n  is  expanded
              to  produce a pattern as described below under PPaatttteerrnn MMaattcchhiinngg.
              BBaasshh then examines characters in the expanded value of _p_a_r_a_m_e_t_e_r
              against _p_a_t_t_e_r_n as described below.  If a character matches  the
              pattern,  its case is converted.  The pattern should not attempt
              to match more than one character.

              Using "^" converts lowercase letters matching _p_a_t_t_e_r_n to  upper-
              case; "," converts matching uppercase letters to lowercase.  The
              ^^  and  ,,  variants  examine the first character in the expanded
              value and convert its case if it matches _p_a_t_t_e_r_n; the ^^^^ and  ,,,,
              variants  examine  all characters in the expanded value and con-
              vert each one that matches _p_a_t_t_e_r_n.  If _p_a_t_t_e_r_n is  omitted,  it
              is treated like a ??, which matches every character.

              If  _p_a_r_a_m_e_t_e_r  is @@ or **, the case modification operation is ap-
              plied to each positional parameter in turn, and the expansion is
              the resultant list.  If _p_a_r_a_m_e_t_e_r  is  an  array  variable  sub-
              scripted with @@ or **, the case modification operation is applied
              to  each  member  of the array in turn, and the expansion is the
              resultant list.

       ${_p_a_r_a_m_e_t_e_r@@_o_p_e_r_a_t_o_r}
              PPaarraammeetteerr ttrraannssffoorrmmaattiioonn.  The expansion is either a transforma-
              tion of the value of _p_a_r_a_m_e_t_e_r or  information  about  _p_a_r_a_m_e_t_e_r
              itself,  depending on the value of _o_p_e_r_a_t_o_r.  Each _o_p_e_r_a_t_o_r is a
              single letter:
              UU      The expansion is a string that is the value of  _p_a_r_a_m_e_t_e_r
                     with  lowercase alphabetic characters converted to upper-
                     case.
              uu      The expansion is a string that is the value of  _p_a_r_a_m_e_t_e_r
                     with the first character converted to uppercase, if it is
                     alphabetic.
              LL      The  expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
                     with uppercase alphabetic characters converted to  lower-
                     case.
              QQ      The  expansion is a string that is the value of _p_a_r_a_m_e_t_e_r
                     quoted in a format that can be reused as input.
              EE      The expansion is a string that is the value of  _p_a_r_a_m_e_t_e_r
                     with  backslash  escape  sequences  expanded  as with the
                     $$''...'' quoting mechanism.
              PP      The expansion is a string that is the result of expanding
                     the value of _p_a_r_a_m_e_t_e_r as if it were a prompt string (see
                     PPRROOMMPPTTIINNGG below).
              AA      The expansion is a string in the form  of  an  assignment
                     statement  or  ddeeccllaarree command that, if evaluated, recre-
                     ates _p_a_r_a_m_e_t_e_r with its attributes and value.
              KK      Produces a possibly-quoted version of the value of  _p_a_r_a_-
                     _m_e_t_e_r,  except  that  it prints the values of indexed and
                     associative arrays as  a  sequence  of  quoted  key-value
                     pairs (see AArrrraayyss above).  The keys and values are quoted
                     in a format that can be reused as input.
              aa      The  expansion is a string consisting of flag values rep-
                     resenting _p_a_r_a_m_e_t_e_r's attributes.
              kk      Like the K transformation, but expands the keys and  val-
                     ues  of  indexed and associative arrays to separate words
                     after word splitting.

              If _p_a_r_a_m_e_t_e_r is @@ or **, the operation is applied to  each  posi-
              tional  parameter  in  turn,  and the expansion is the resultant
              list.  If _p_a_r_a_m_e_t_e_r is an array variable subscripted with  @@  or
              **, the operation is applied to each member of the array in turn,
              and the expansion is the resultant list.

              The  result  of  the  expansion is subject to word splitting and
              pathname expansion as described below.

   CCoommmmaanndd SSuubbssttiittuuttiioonn
       _C_o_m_m_a_n_d _s_u_b_s_t_i_t_u_t_i_o_n allows the output of a command to replace the com-
       mand itself.  There are two standard forms:

              $$((_c_o_m_m_a_n_d))
       or (deprecated)
              ``_c_o_m_m_a_n_d``.

       BBaasshh performs the expansion by executing _c_o_m_m_a_n_d in a subshell environ-
       ment and replacing the command substitution with the standard output of
       the command, with any trailing newlines deleted.  Embedded newlines are
       not deleted, but they may be removed during word splitting.   The  com-
       mand  substitution  $$((ccaatt  _f_i_l_e))  can be replaced by the equivalent but
       faster $$((<< _f_i_l_e)).

       With the old-style backquote form of  substitution,  backslash  retains
       its  literal  meaning  except  when  followed by $$, ``, or \\.  The first
       backquote not preceded by a backslash terminates the command  substitu-
       tion.   When  using  the  $(_c_o_m_m_a_n_d)  form,  all characters between the
       parentheses make up the command; none are treated specially.

       There is an alternate form of command substitution:

              $${{_c _c_o_m_m_a_n_d;;}}

       which executes _c_o_m_m_a_n_d in the current execution  environment  and  cap-
       tures its output, again with trailing newlines removed.

       The character _c following the open brace must be a space, tab, newline,
       or  ||,  and the close brace must be in a position where a reserved word
       may appear (i.e., preceded by a command terminator such as  semicolon).
       BBaasshh allows the close brace to be joined to the remaining characters in
       the  word without being followed by a shell metacharacter as a reserved
       word would usually require.

       Any side effects of _c_o_m_m_a_n_d take effect immediately in the current exe-
       cution environment and persist in the  current  environment  after  the
       command completes (e.g., the eexxiitt builtin exits the shell).

       This  type of command substitution superficially resembles executing an
       unnamed shell function: local variables are created  as  when  a  shell
       function  is  executing,  and the rreettuurrnn builtin forces _c_o_m_m_a_n_d to com-
       plete; however, the rest of the execution  environment,  including  the
       positional parameters, is shared with the caller.

       If  the  first character following the open brace is a ||, the construct
       expands to the value of the RREEPPLLYY shell  variable  after  _c_o_m_m_a_n_d  exe-
       cutes,  without removing any trailing newlines, and the standard output
       of _c_o_m_m_a_n_d remains the same as in the calling shell.  BBaasshh creates  RREE--
       PPLLYY as an initially-unset local variable when _c_o_m_m_a_n_d executes, and re-
       stores  RREEPPLLYY to the value it had before the command substitution after
       _c_o_m_m_a_n_d completes, as with any local variable.

       Command substitutions may be nested.  To nest when using the backquoted
       form, escape the inner backquotes with backslashes.

       If the substitution appears within double quotes, bbaasshh does not perform
       word splitting and pathname expansion on the results.

   AArriitthhmmeettiicc EExxppaannssiioonn
       Arithmetic expansion evaluates an arithmetic expression and substitutes
       the result.  The format for arithmetic expansion is:

              $$((((_e_x_p_r_e_s_s_i_o_n))))

       The _e_x_p_r_e_s_s_i_o_n undergoes the same expansions as if it were within  dou-
       ble quotes, but unescaped double quote characters in _e_x_p_r_e_s_s_i_o_n are not
       treated  specially  and  are removed.  All tokens in the expression un-
       dergo parameter and variable expansion, command substitution, and quote
       removal.  The result is treated as  the  arithmetic  expression  to  be
       evaluated.   Since  the  way Bash handles double quotes can potentially
       result in empty strings, arithmetic expansion treats those  as  expres-
       sions that evaluate to 0.  Arithmetic expansions may be nested.

       The  evaluation  is performed according to the rules listed below under
       AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN.  If _e_x_p_r_e_s_s_i_o_n is invalid, bbaasshh prints a message
       to standard error indicating failure, does not  perform  the  substitu-
       tion, and does not execute the command associated with the expansion.

   PPrroocceessss SSuubbssttiittuuttiioonn
       _P_r_o_c_e_s_s  _s_u_b_s_t_i_t_u_t_i_o_n allows a process's input or output to be referred
       to using a filename.  It takes the form of  <<((_l_i_s_t))  or  >>((_l_i_s_t)).   The
       process  _l_i_s_t is run asynchronously, and its input or output appears as
       a filename.  This filename is passed as an argument to the current com-
       mand as the result of the expansion.

       If the >>((_l_i_s_t)) form is used, writing to the  file  provides  input  for
       _l_i_s_t.  If the <<((_l_i_s_t)) form is used, reading the file obtains the output
       of _l_i_s_t.  No space may appear between the << or >> and the left parenthe-
       sis, otherwise the construct would be interpreted as a redirection.

       Process  substitution  is supported on systems that support named pipes
       (_F_I_F_O_s) or the _/_d_e_v_/_f_d method of naming open files.

       When available, process substitution is performed  simultaneously  with
       parameter  and variable expansion, command substitution, and arithmetic
       expansion.

   WWoorrdd SSpplliittttiinngg
       The shell scans the results of parameter expansion,  command  substitu-
       tion,  and arithmetic expansion that did not occur within double quotes
       for _w_o_r_d _s_p_l_i_t_t_i_n_g.  Words that were not expanded are not split.

       The shell treats each character of IIFFSS as a delimiter, and  splits  the
       results  of  the  other expansions into words using these characters as
       field terminators.

       An _I_F_S _w_h_i_t_e_s_p_a_c_e character is whitespace as defined above (see DDeeffiinnii--
       ttiioonnss) that appears in the value of IIFFSS.  Space, tab, and  newline  are
       always  considered IFS whitespace, even if they don't appear in the lo-
       cale's ssppaaccee category.

       If  IIFFSS  is  unset,  field  splitting  acts  as  if  its   value   were
       <<ssppaaccee>><<ttaabb>><<nneewwlliinnee>>,  and  treats these characters as IFS whitespace.
       If the value of IIFFSS is null, no word  splitting  occurs,  but  implicit
       null arguments (see below) are still removed.

       Word  splitting  begins by removing sequences of IFS whitespace charac-
       ters from the beginning and end of the results of the  previous  expan-
       sions, then splits the remaining words.

       If  the value of IIFFSS consists solely of IFS whitespace, any sequence of
       IFS whitespace characters delimits a field,  so  a  field  consists  of
       characters that are not unquoted IFS whitespace, and null fields result
       only from quoting.

       If  IIFFSS  contains a non-whitespace character, then any character in the
       value of IIFFSS that is not IFS whitespace, along with  any  adjacent  IFS
       whitespace characters, delimits a field.  This means that adjacent non-
       IFS-whitespace  delimiters  produce  a  null  field.  A sequence of IFS
       whitespace characters also delimits a field.

       Explicit null arguments ("""" or '''') are retained and passed to  commands
       as empty strings.  Unquoted implicit null arguments, resulting from the
       expansion  of parameters that have no values, are removed.  Expanding a
       parameter with no value within double quotes  produces  a  null  field,
       which is retained and passed to a command as an empty string.

       When  a  quoted null argument appears as part of a word whose expansion
       is non-null, word splitting removes the null argument portion,  leaving
       the  non-null  expansion.   That is, the word "-d''" becomes "-d" after
       word splitting and null argument removal.

   PPaatthhnnaammee EExxppaannssiioonn
       After word splitting, unless the --ff option has  been  set,  bbaasshh  scans
       each  word  for the characters **, ??, and [[.  If one of these characters
       appears, and is not quoted, then the word is regarded as a _p_a_t_t_e_r_n, and
       replaced with a sorted list of filenames matching the pattern (see PPaatt--
       tteerrnn MMaattcchhiinngg below) subject to the value of the GGLLOOBBSSOORRTT  shell  vari-
       able.

       If  no  matching  filenames are found, and the shell option nnuullllgglloobb is
       not enabled, the word is left unchanged.  If  the  nnuullllgglloobb  option  is
       set,  and  no  matches are found, the word is removed.  If the ffaaiillgglloobb
       shell option is set, and no matches are found,  bbaasshh  prints  an  error
       message  and does not execute the command.  If the shell option nnooccaassee--
       gglloobb is enabled, the match is performed without regard to the  case  of
       alphabetic characters.

       When a pattern is used for pathname expansion, the character "." at the
       start  of  a  name or immediately following a slash must be matched ex-
       plicitly, unless the shell option ddoottgglloobb is set.  In  order  to  match
       the  filenames  _. and _._., the pattern must begin with "." (for example,
       ".?"), even if ddoottgglloobb is set.  If the gglloobbsskkiippddoottss shell option is en-
       abled, the filenames _. and _._. never match, even if the  pattern  begins
       with  a  ".".   When  not  matching pathnames, the "." character is not
       treated specially.

       When matching a pathname, the slash character must  always  be  matched
       explicitly by a slash in the pattern, but in other matching contexts it
       can  be matched by a special pattern character as described below under
       PPaatttteerrnn MMaattcchhiinngg.

       See the description of sshhoopptt below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS  for  a
       description  of  the  nnooccaasseegglloobb, nnuullllgglloobb, gglloobbsskkiippddoottss, ffaaiillgglloobb, and
       ddoottgglloobb shell options.

       The GGLLOOBBIIGGNNOORREE shell variable may be used to restrict the set  of  file
       names  matching  a  _p_a_t_t_e_r_n.   If GGLLOOBBIIGGNNOORREE is set, each matching file
       name that also matches one of the patterns  in  GGLLOOBBIIGGNNOORREE  is  removed
       from  the list of matches.  If the nnooccaasseegglloobb option is set, the match-
       ing against the patterns in GGLLOOBBIIGGNNOORREE is performed without  regard  to
       case.  The filenames _. and _._. are always ignored when GGLLOOBBIIGGNNOORREE is set
       and  not null.  However, setting GGLLOOBBIIGGNNOORREE to a non-null value has the
       effect of enabling the ddoottgglloobb shell option, so all other filenames be-
       ginning with a "." match.  To get the old behavior  of  ignoring  file-
       names  beginning  with a ".", make ".*"  one of the patterns in GGLLOOBBIIGG--
       NNOORREE.  The ddoottgglloobb option is disabled when GGLLOOBBIIGGNNOORREE  is  unset.   The
       GGLLOOBBIIGGNNOORREE pattern matching honors the setting of the eexxttgglloobb shell op-
       tion.

       The  value  of  the GGLLOOBBSSOORRTT shell variable controls how the results of
       pathname expansion are sorted, as described  above  under  SShheellll  VVaarrii--
       aabblleess.

       PPaatttteerrnn MMaattcchhiinngg

       Any character that appears in a pattern, other than the special pattern
       characters  described below, matches itself.  The NUL character may not
       occur in a pattern.  A backslash escapes the following  character;  the
       escaping  backslash  is  discarded  when matching.  The special pattern
       characters must be quoted if they are to be matched literally.

       The special pattern characters have the following meanings:

              **      Matches any string, including the null string.  When  the
                     gglloobbssttaarr  shell  option  is  enabled,  and ** is used in a
                     pathname expansion context, two adjacent  **s  used  as  a
                     single  pattern match all files and zero or more directo-
                     ries and subdirectories.  If followed by a //,  two  adja-
                     cent **s match only directories and subdirectories.
              ??      Matches any single character.
              [[...]]  Matches  any  one  of the characters enclosed between the
                     brackets.  This is known  as  a  _b_r_a_c_k_e_t  _e_x_p_r_e_s_s_i_o_n  and
                     matches  a  single character.  A pair of characters sepa-
                     rated by a hyphen denotes a _r_a_n_g_e _e_x_p_r_e_s_s_i_o_n; any charac-
                     ter that falls between those two  characters,  inclusive,
                     using the current locale's collating sequence and charac-
                     ter set, matches.  If the first character following the [[
                     is  a  !!   or a ^^ then any character not within the range
                     matches.  To match a --, include it as the first  or  last
                     character  in  the  set.  To match a ]], include it as the
                     first character in the set.

                     The sorting order of characters in range expressions, and
                     the characters included in the range, are  determined  by
                     the  current  locale  and the values of the LLCC__CCOOLLLLAATTEE or
                     LLCC__AALLLL shell variables, if set.   To  obtain  the  tradi-
                     tional  interpretation  of range expressions, where [[aa--dd]]
                     is equivalent to [[aabbccdd]], set the value of the  LLCC__CCOOLLLLAATTEE
                     or  LLCC__AALLLL  shell variables to CC, or enable the gglloobbaassccii--
                     iirraannggeess shell option.

                     Within a bracket expression,  _c_h_a_r_a_c_t_e_r  _c_l_a_s_s_e_s  can  be
                     specified  using the syntax [[::_c_l_a_s_s::]], where _c_l_a_s_s is one
                     of the following classes defined in the POSIX standard:

                     aallnnuumm aallpphhaa aasscciiii bbllaannkk ccnnttrrll  ddiiggiitt  ggrraapphh  lloowweerr  pprriinntt
                     ppuunncctt ssppaaccee uuppppeerr wwoorrdd xxddiiggiitt

                     A character class matches any character belonging to that
                     class.  The wwoorrdd character class matches letters, digits,
                     and the character _.

                     Within  a bracket expression, an _e_q_u_i_v_a_l_e_n_c_e _c_l_a_s_s can be
                     specified using the syntax [[==_c==]], which matches all char-
                     acters with the same collation weight (as defined by  the
                     current locale) as the character _c.

                     Within   a  bracket  expression,  the  syntax  [[.._s_y_m_b_o_l..]]
                     matches the collating symbol _s_y_m_b_o_l.

       If the eexxttgglloobb shell option is enabled using  the  sshhoopptt  builtin,  the
       shell  recognizes  several extended pattern matching operators.  In the
       following description, a _p_a_t_t_e_r_n_-_l_i_s_t is a list of one or more patterns
       separated by a ||.  Composite patterns may be formed using one  or  more
       of the following sub-patterns:

              ??((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches zero or one occurrence of the given patterns.
              **((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches zero or more occurrences of the given patterns.
              ++((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches one or more occurrences of the given patterns.
              @@((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches one of the given patterns.
              !!((_p_a_t_t_e_r_n_-_l_i_s_t))
                     Matches anything except one of the given patterns.

       The eexxttgglloobb option changes the behavior of the parser, since the paren-
       theses  are  normally  treated as operators with syntactic meaning.  To
       ensure that extended matching patterns are parsed correctly, make  sure
       that  eexxttgglloobb  is enabled before parsing constructs containing the pat-
       terns, including shell functions and command substitutions.

       When matching filenames, the ddoottgglloobb shell option determines the set of
       filenames that are tested: when ddoottgglloobb is enabled, the  set  of  file-
       names  includes  all  files  beginning  with  ".", but _. and _._. must be
       matched by a pattern or sub-pattern that begins with a dot; when it  is
       disabled, the set does not include any filenames beginning with "." un-
       less the pattern or sub-pattern begins with a ".".  If the gglloobbsskkiippddoottss
       shell  option  is  enabled,  the filenames _. and _._. never appear in the
       set.  As above, "." only has a special meaning when matching filenames.

       Complicated extended pattern matching against long strings is slow, es-
       pecially when the patterns contain alternations and the strings contain
       multiple matches.  Using separate matches against shorter  strings,  or
       using arrays of strings instead of a single long string, may be faster.

   QQuuoottee RReemmoovvaall
       After the preceding expansions, all unquoted occurrences of the charac-
       ters  \\,  '', and "" that did not result from one of the above expansions
       are removed.

RREEDDIIRREECCTTIIOONN
       Before a command is executed, its input and output  may  be  _r_e_d_i_r_e_c_t_e_d
       using  a special notation interpreted by the shell.  _R_e_d_i_r_e_c_t_i_o_n allows
       commands' file handles to be duplicated, opened, closed, made to  refer
       to different files, and can change the files the command reads from and
       writes  to.   When used with the eexxeecc builtin, redirections modify file
       handles in the current  shell  execution  environment.   The  following
       redirection  operators  may  precede or appear anywhere within a _s_i_m_p_l_e
       _c_o_m_m_a_n_d or may follow a _c_o_m_m_a_n_d.  Redirections are processed in the or-
       der they appear, from left to right.

       Each redirection that may be preceded by a file descriptor  number  may
       instead be preceded by a word of the form {_v_a_r_n_a_m_e}.  In this case, for
       each  redirection  operator  except  >>&&-- and <<&&--, the shell allocates a
       file descriptor greater than or equal to 10 and assigns it to  _v_a_r_n_a_m_e.
       If {_v_a_r_n_a_m_e} precedes >>&&-- or <<&&--, the value of _v_a_r_n_a_m_e defines the file
       descriptor  to  close.   If {_v_a_r_n_a_m_e} is supplied, the redirection per-
       sists beyond the scope of the command, which allows the shell  program-
       mer to manage the file descriptor's lifetime manually without using the
       eexxeecc builtin.  The vvaarrrreeddiirr__cclloossee shell option manages this behavior.

       In  the  following descriptions, if the file descriptor number is omit-
       ted, and the first character of the redirection operator  is  "<",  the
       redirection  refers  to the standard input (file descriptor 0).  If the
       first character of the redirection operator  is  ">",  the  redirection
       refers to the standard output (file descriptor 1).

       The  _w_o_r_d  following the redirection operator in the following descrip-
       tions, unless otherwise noted, is subjected to brace  expansion,  tilde
       expansion,  parameter  and  variable  expansion,  command substitution,
       arithmetic expansion,  quote  removal,  pathname  expansion,  and  word
       splitting.  If it expands to more than one word, bbaasshh reports an error.

       The order of redirections is significant.  For example, the command

              ls >> dirlist 2>>&&1

       directs  both  standard  output and standard error to the file _d_i_r_l_i_s_t,
       while the command

              ls 2>>&&1 >> dirlist

       directs only the standard output to file _d_i_r_l_i_s_t, because the  standard
       error  was  directed  to the standard output before the standard output
       was redirected to _d_i_r_l_i_s_t.

       BBaasshh handles several filenames specially when they are used in redirec-
       tions, as described in the following table.  If the operating system on
       which bbaasshh is running provides these special  files,  bbaasshh  uses  them;
       otherwise  it  emulates them internally with the behavior described be-
       low.

              //ddeevv//ffdd//_f_d
                     If _f_d is a valid integer, duplicate file descriptor _f_d.
              //ddeevv//ssttddiinn
                     File descriptor 0 is duplicated.
              //ddeevv//ssttddoouutt
                     File descriptor 1 is duplicated.
              //ddeevv//ssttddeerrrr
                     File descriptor 2 is duplicated.
              //ddeevv//ttccpp//_h_o_s_t//_p_o_r_t
                     If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t
                     is an integer port number or service name, bbaasshh  attempts
                     to open the corresponding TCP socket.
              //ddeevv//uuddpp//_h_o_s_t//_p_o_r_t
                     If _h_o_s_t is a valid hostname or Internet address, and _p_o_r_t
                     is  an integer port number or service name, bbaasshh attempts
                     to open the corresponding UDP socket.

       A failure to open or create a file causes the redirection to fail.

       Redirections using file descriptors greater than 9 should be used  with
       care,  as they may conflict with file descriptors the shell uses inter-
       nally.

   RReeddiirreeccttiinngg IInnppuutt
       Redirecting input opens the file whose name results from the  expansion
       of  _w_o_r_d  for reading on file descriptor _n, or the standard input (file
       descriptor 0) if _n is not specified.

       The general format for redirecting input is:

              [_n]<<_w_o_r_d

   RReeddiirreeccttiinngg OOuuttppuutt
       Redirecting output opens the file whose name results from the expansion
       of _w_o_r_d for writing on file descriptor _n, or the standard output  (file
       descriptor  1) if _n is not specified.  If the file does not exist it is
       created; if it does exist it is truncated to zero size.

       The general format for redirecting output is:

              [_n]>>_w_o_r_d

       If the redirection operator is >>, and the nnoocclloobbbbeerr option to  the  sseett
       builtin  command  has  been  enabled, the redirection fails if the file
       whose name results from the expansion of _w_o_r_d exists and is  a  regular
       file.   If  the redirection operator is >>||, or the redirection operator
       is >> and the nnoocclloobbbbeerr option to the sseett builtin is not  enabled,  bbaasshh
       attempts the redirection even if the file named by _w_o_r_d exists.

   AAppppeennddiinngg RReeddiirreecctteedd OOuuttppuutt
       Redirecting  output  in  this fashion opens the file whose name results
       from the expansion of _w_o_r_d for appending on file descriptor _n,  or  the
       standard output (file descriptor 1) if _n is not specified.  If the file
       does not exist it is created.

       The general format for appending output is:

              [_n]>>>>_w_o_r_d

   RReeddiirreeccttiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
       This  construct  redirects both the standard output (file descriptor 1)
       and the standard error output (file descriptor 2)  to  the  file  whose
       name is the expansion of _w_o_r_d.

       There  are two formats for redirecting standard output and standard er-
       ror:

              &&>>_w_o_r_d
       and
              >>&&_w_o_r_d

       Of the two forms, the first is preferred.  This is semantically equiva-
       lent to

              >>_w_o_r_d 2>>&&1

       When using the second form, _w_o_r_d may not expand to a number or  --.   If
       it  does,  other  redirection operators apply (see DDuupplliiccaattiinngg FFiillee DDee--
       ssccrriippttoorrss below) for compatibility reasons.

   AAppppeennddiinngg SSttaannddaarrdd OOuuttppuutt aanndd SSttaannddaarrdd EErrrroorr
       This construct appends both the standard output (file descriptor 1) and
       the standard error output (file descriptor 2) to the file whose name is
       the expansion of _w_o_r_d.

       The format for appending standard output and standard error is:

              &&>>>>_w_o_r_d

       This is semantically equivalent to

              >>>>_w_o_r_d 2>>&&1

       (see DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss below).

   HHeerree DDooccuummeennttss
       This type of redirection instructs the shell to  read  input  from  the
       current source until it reads a line containing only _d_e_l_i_m_i_t_e_r (with no
       trailing  blanks).   All of the lines read up to that point then become
       the standard input (or file descriptor _n if _n is specified) for a  com-
       mand.

       The format of here-documents is:

              [_n]<<<<[--]_w_o_r_d
                      _h_e_r_e_-_d_o_c_u_m_e_n_t
              _d_e_l_i_m_i_t_e_r

       The  shell  does  not perform parameter and variable expansion, command
       substitution, arithmetic expansion, or pathname expansion on _w_o_r_d.

       If any part of _w_o_r_d is quoted, the _d_e_l_i_m_i_t_e_r is the result of quote re-
       moval on _w_o_r_d, and the lines in the here-document are not expanded.  If
       _w_o_r_d is unquoted, the _d_e_l_i_m_i_t_e_r is _w_o_r_d itself, and  the  here-document
       text  is  treated similarly to a double-quoted string: all lines of the
       here-document are subjected to parameter expansion,  command  substitu-
       tion,  and  arithmetic  expansion, the character sequence \\<<nneewwlliinnee>> is
       treated literally, and \\ must be used to quote the characters \\, $$, and
       ``; however, double quote characters have no special meaning.

       If the redirection operator is <<<<--, then the shell strips  all  leading
       tab  characters  from  input  lines  and the line containing _d_e_l_i_m_i_t_e_r.
       This allows here-documents within shell scripts to  be  indented  in  a
       natural fashion.

       If the delimiter is not quoted, the \\<<nneewwlliinnee>> sequence is treated as a
       line  continuation:  the two lines are joined and the backslash-newline
       is removed.  This happens while reading the here-document,  before  the
       check for the ending delimiter, so joined lines can form the end delim-
       iter.

   HHeerree SSttrriinnggss
       A variant of here documents, the format is:

              [_n]<<<<<<_w_o_r_d

       The  _w_o_r_d  undergoes tilde expansion, parameter and variable expansion,
       command substitution, arithmetic expansion, and quote  removal.   Path-
       name  expansion  and  word  splitting are not performed.  The result is
       supplied as a single string, with a newline appended, to the command on
       its standard input (or file descriptor _n if _n is specified).

   DDuupplliiccaattiinngg FFiillee DDeessccrriippttoorrss
       The redirection operator

              [_n]<<&&_w_o_r_d

       is used to duplicate input file descriptors.  If _w_o_r_d expands to one or
       more digits, file descriptor _n is made to be a copy of  that  file  de-
       scriptor.  It is a redirection error if the digits in _w_o_r_d do not spec-
       ify a file descriptor open for input.  If _w_o_r_d evaluates to --, file de-
       scriptor  _n  is  closed.  If _n is not specified, this uses the standard
       input (file descriptor 0).

       The operator

              [_n]>>&&_w_o_r_d

       is used similarly to duplicate output file descriptors.  If  _n  is  not
       specified,  this uses the standard output (file descriptor 1).  It is a
       redirection error if the digits in _w_o_r_d do not specify a file  descrip-
       tor  open  for  output.   If  _w_o_r_d evaluates to --, file descriptor _n is
       closed.  As a special case, if _n is omitted, and _w_o_r_d does  not  expand
       to  one  or  more  digits  or --, this redirects the standard output and
       standard error as described previously.

   MMoovviinngg FFiillee DDeessccrriippttoorrss
       The redirection operator

              [_n]<<&&_d_i_g_i_t--

       moves the file descriptor _d_i_g_i_t to file descriptor _n, or  the  standard
       input (file descriptor 0) if _n is not specified.  _d_i_g_i_t is closed after
       being duplicated to _n.

       Similarly, the redirection operator

              [_n]>>&&_d_i_g_i_t--

       moves  the  file descriptor _d_i_g_i_t to file descriptor _n, or the standard
       output (file descriptor 1) if _n is not specified.

   OOppeenniinngg FFiillee DDeessccrriippttoorrss ffoorr RReeaaddiinngg aanndd WWrriittiinngg
       The redirection operator

              [_n]<<>>_w_o_r_d

       opens the file whose name is the expansion of _w_o_r_d for both reading and
       writing on file descriptor _n, or on file descriptor 0 if _n is not spec-
       ified.  If the file does not exist, it is created.

AALLIIAASSEESS
       _A_l_i_a_s_e_s allow a string to be substituted for a word that is in a  posi-
       tion  in  the input where it can be the first word of a simple command.
       Aliases have names and corresponding values that are set and unset  us-
       ing  the aalliiaass and uunnaalliiaass builtin commands (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
       below).

       If the shell reads an unquoted word in the right  position,  it  checks
       the  word to see if it matches an alias name.  If it matches, the shell
       replaces the word with the alias value, and reads that value as  if  it
       had been read instead of the word.  The shell doesn't look at any char-
       acters following the word before attempting alias substitution.

       The  characters  //,  $$, ``, and == and any of the shell _m_e_t_a_c_h_a_r_a_c_t_e_r_s or
       quoting characters listed above may not appear in an alias  name.   The
       replacement  text  may  contain  any valid shell input, including shell
       metacharacters.  The first word of the replacement text is  tested  for
       aliases, but a word that is identical to an alias being expanded is not
       expanded a second time.  This means that one may alias llss to llss --FF, for
       instance,  and  bbaasshh does not try to recursively expand the replacement
       text.

       If the last character of the alias value is a _b_l_a_n_k, the  shell  checks
       the next command word following the alias for alias expansion.

       Aliases are created and listed with the aalliiaass command, and removed with
       the uunnaalliiaass command.

       There  is no mechanism for using arguments in the replacement text.  If
       arguments are needed, use a shell function (see  FFUUNNCCTTIIOONNSS  below)  in-
       stead.

       Aliases  are not expanded when the shell is not interactive, unless the
       eexxppaanndd__aalliiaasseess shell option is set using sshhoopptt (see the description  of
       sshhoopptt under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       The  rules  concerning  the  definition and use of aliases are somewhat
       confusing.  BBaasshh always reads at least one complete line of input,  and
       all  lines that make up a compound command, before executing any of the
       commands on that line or the compound command.   Aliases  are  expanded
       when  a  command is read, not when it is executed.  Therefore, an alias
       definition appearing on the same line as another command does not  take
       effect until the shell reads the next line of input, and an alias defi-
       nition  in  a  compound  command  does  not take effect until the shell
       parses and executes the entire compound command.  The commands  follow-
       ing  the  alias  definition  on that line, or in the rest of a compound
       command, are not affected by the new alias.  This behavior is  also  an
       issue  when  functions are executed.  Aliases are expanded when a func-
       tion definition is read, not when the function is executed,  because  a
       function definition is itself a command.  As a consequence, aliases de-
       fined in a function are not available until after that function is exe-
       cuted.   To  be  safe, always put alias definitions on a separate line,
       and do not use aalliiaass in compound commands.

       For almost every purpose, shell functions are preferable to aliases.

FFUUNNCCTTIIOONNSS
       A shell function, defined  as  described  above  under  SSHHEELLLL  GGRRAAMMMMAARR,
       stores  a  series  of commands for later execution.  When the name of a
       shell function is used as a simple command name, the shell executes the
       list of commands associated with that function name.  Functions are ex-
       ecuted in the context of the calling shell; there  is  no  new  process
       created  to interpret them (contrast this with the execution of a shell
       script).

       When a function is executed, the arguments to the function  become  the
       positional parameters during its execution.  The special parameter ## is
       updated  to reflect the new positional parameters.  Special parameter 00
       is unchanged.  The first element of the FFUUNNCCNNAAMMEE variable is set to the
       name of the function while the function is executing.

       All other aspects of the shell execution environment are identical  be-
       tween  a  function  and its caller with these exceptions: the DDEEBBUUGG and
       RREETTUURRNN traps (see the description  of  the  ttrraapp  builtin  under  SSHHEELLLL
       BBUUIILLTTIINN  CCOOMMMMAANNDDSS below) are not inherited unless the function has been
       given the ttrraaccee attribute (see the description of the  ddeeccllaarree  builtin
       below)  or  the --oo ffuunnccttrraaccee shell option has been enabled with the sseett
       builtin (in which case all  functions  inherit  the  DDEEBBUUGG  and  RREETTUURRNN
       traps),  and the EERRRR trap is not inherited unless the --oo eerrrrttrraaccee shell
       option has been enabled.

       Variables local to the function are declared  with  the  llooccaall  builtin
       command  (_l_o_c_a_l _v_a_r_i_a_b_l_e_s).  Ordinarily, variables and their values are
       shared between the function and its caller.  If a variable is  declared
       llooccaall,  the variable's visible scope is restricted to that function and
       its children (including the functions it calls).

       In the following description, the _c_u_r_r_e_n_t _s_c_o_p_e is a currently- execut-
       ing function.  Previous scopes consist of that function's caller and so
       on, back to the "global" scope, where the shell is  not  executing  any
       shell  function.   A  local variable at the current scope is a variable
       declared using the llooccaall or ddeeccllaarree builtins in the  function  that  is
       currently executing.

       Local  variables "shadow" variables with the same name declared at pre-
       vious scopes.  For instance, a local variable declared  in  a  function
       hides variables with the same name declared at previous scopes, includ-
       ing  global  variables:  references  and assignments refer to the local
       variable, leaving the variables at previous  scopes  unmodified.   When
       the function returns, the global variable is once again visible.

       The  shell  uses  _d_y_n_a_m_i_c  _s_c_o_p_i_n_g  to  control a variable's visibility
       within functions.  With dynamic scoping, visible  variables  and  their
       values  are a result of the sequence of function calls that caused exe-
       cution to reach the current function.  The value of a variable  that  a
       function  sees  depends on its value within its caller, if any, whether
       that caller is the global scope or another  shell  function.   This  is
       also the value that a local variable declaration shadows, and the value
       that is restored when the function returns.

       For  example, if a variable _v_a_r is declared as local in function _f_u_n_c_1,
       and _f_u_n_c_1 calls another function _f_u_n_c_2, references  to  _v_a_r  made  from
       within  _f_u_n_c_2  resolve  to the local variable _v_a_r from _f_u_n_c_1, shadowing
       any global variable named _v_a_r.

       The uunnsseett builtin also acts using the same dynamic scope: if a variable
       is local to the current scope, uunnsseett unsets  it;  otherwise  the  unset
       will  refer  to  the  variable  found in any calling scope as described
       above.  If a variable at the current local scope is unset,  it  remains
       so  (appearing  as  unset) until it is reset in that scope or until the
       function returns.  Once the function returns, any instance of the vari-
       able at a previous scope becomes visible.  If the unset acts on a vari-
       able at a previous scope, any instance of a  variable  with  that  name
       that  had been shadowed becomes visible (see below how the llooccaallvvaarr__uunn--
       sseett shell option changes this behavior).

       The FFUUNNCCNNEESSTT variable, if set to a numeric value greater  than  0,  de-
       fines  a maximum function nesting level.  Function invocations that ex-
       ceed the limit cause the entire command to abort.

       If the builtin command rreettuurrnn is executed in a function,  the  function
       completes  and  execution resumes with the next command after the func-
       tion call.  If rreettuurrnn is supplied a numeric argument, that is the func-
       tion's return status; otherwise the function's  return  status  is  the
       exit  status  of the last command executed before the rreettuurrnn.  Any com-
       mand associated with the RREETTUURRNN trap is executed before  execution  re-
       sumes.  When a function completes, the values of the positional parame-
       ters  and  the  special parameter ## are restored to the values they had
       prior to the function's execution.

       The --ff option to the ddeeccllaarree or ttyyppeesseett builtin commands lists function
       names and definitions.  The --FF option to ddeeccllaarree or ttyyppeesseett  lists  the
       function names only (and optionally the source file and line number, if
       the  eexxttddeebbuugg  shell  option is enabled).  Functions may be exported so
       that child shell processes (those created  when  executing  a  separate
       shell invocation) automatically have them defined with the --ff option to
       the eexxppoorrtt builtin.  The --ff option to the uunnsseett builtin deletes a func-
       tion definition.

       Functions may be recursive.  The FFUUNNCCNNEESSTT variable may be used to limit
       the  depth  of the function call stack and restrict the number of func-
       tion invocations.  By default, bbaasshh imposes no limit on the  number  of
       recursive calls.

AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN
       The  shell allows arithmetic expressions to be evaluated, under certain
       circumstances (see the lleett and ddeeccllaarree builtin commands,  the  ((((  com-
       pound  command, the arithmetic ffoorr command, the [[[[ conditional command,
       and AArriitthhmmeettiicc EExxppaannssiioonn).

       Evaluation is done in the largest fixed-width integers available,  with
       no  check  for overflow, though division by 0 is trapped and flagged as
       an error.  The operators and their precedence, associativity, and  val-
       ues are the same as in the C language.  The following list of operators
       is  grouped  into levels of equal-precedence operators.  The levels are
       listed in order of decreasing precedence.

       _i_d++++ _i_d----
              variable post-increment and post-decrement
       ++++_i_d ----_i_d
              variable pre-increment and pre-decrement
       -- ++    unary minus and plus
       !! ~~    logical and bitwise negation
       ****     exponentiation
       ** // %%  multiplication, division, remainder
       ++ --    addition, subtraction
       <<<< >>>>  left and right bitwise shifts
       <<== >>== << >>
              comparison
       ==== !!==  equality and inequality
       &&      bitwise AND
       ^^      bitwise exclusive OR
       ||      bitwise OR
       &&&&     logical AND
       ||||     logical OR
       _e_x_p_r??_e_x_p_r::_e_x_p_r
              conditional operator
       == **== //== %%== ++== --== <<<<== >>>>== &&== ^^== ||==
              assignment
       _e_x_p_r_1 ,, _e_x_p_r_2
              comma

       Shell variables are allowed as operands; parameter  expansion  is  per-
       formed before the expression is evaluated.  Within an expression, shell
       variables  may  also  be referenced by name without using the parameter
       expansion syntax.  This means you can use "x", where _x is a shell vari-
       able name, in an arithmetic expression, and the shell will evaluate its
       value as an expression and use the result.  A shell  variable  that  is
       null or unset evaluates to 0 when referenced by name in an expression.

       The  value  of a variable is evaluated as an arithmetic expression when
       it is referenced, or when a variable which has been given  the  _i_n_t_e_g_e_r
       attribute using ddeeccllaarree --ii is assigned a value.  A null value evaluates
       to  0.   A shell variable need not have its _i_n_t_e_g_e_r attribute turned on
       to be used in an expression.

       Integer constants follow the C language definition, without suffixes or
       character constants.  Constants with a leading 0 are interpreted as oc-
       tal numbers.  A leading 0x or 0X denotes hexadecimal.  Otherwise,  num-
       bers  take the form [_b_a_s_e_#]n, where the optional _b_a_s_e is a decimal num-
       ber between 2 and 64 representing the arithmetic base, and _n is a  num-
       ber  in  that  base.   If _b_a_s_e_# is omitted, then base 10 is used.  When
       specifying _n, if a non-digit is required, the digits greater than 9 are
       represented by the lowercase letters, the uppercase letters, @, and  _,
       in  that order.  If _b_a_s_e is less than or equal to 36, lowercase and up-
       percase letters may be used interchangeably to  represent  numbers  be-
       tween 10 and 35.

       Operators are evaluated in precedence order.  Sub-expressions in paren-
       theses are evaluated first and may override the precedence rules above.

CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS
       Conditional  expressions  are  used  by the [[[[ compound command and the
       tteesstt and [[ builtin commands to test file attributes and perform  string
       and  arithmetic  comparisons.   The tteesstt and [[ commands determine their
       behavior based on the number of  arguments;  see  the  descriptions  of
       those commands for any other command-specific actions.

       Expressions are formed from the unary or binary primaries listed below.
       Unary  expressions  are  often  used to examine the status of a file or
       shell variable.  Binary operators are used  for  string,  numeric,  and
       file attribute comparisons.

       BBaasshh  handles several filenames specially when they are used in expres-
       sions.  If the operating system on which bbaasshh is running provides these
       special files, bash will use them; otherwise it will emulate  them  in-
       ternally  with  this  behavior: If any _f_i_l_e argument to one of the pri-
       maries is of the form _/_d_e_v_/_f_d_/_n, then bbaasshh checks  file  descriptor  _n.
       If  the  _f_i_l_e  argument  to  one of the primaries is one of _/_d_e_v_/_s_t_d_i_n,
       _/_d_e_v_/_s_t_d_o_u_t, or _/_d_e_v_/_s_t_d_e_r_r, bbaasshh checks file descriptor 0,  1,  or  2,
       respectively.

       Unless otherwise specified, primaries that operate on files follow sym-
       bolic links and operate on the target of the link, rather than the link
       itself.

       When  used with [[[[, or when the shell is in posix mode, the << and >> op-
       erators sort lexicographically using  the  current  locale.   When  the
       shell  is  not in posix mode, the tteesstt command sorts using ASCII order-
       ing.

       --aa _f_i_l_e
              True if _f_i_l_e exists.
       --bb _f_i_l_e
              True if _f_i_l_e exists and is a block special file.
       --cc _f_i_l_e
              True if _f_i_l_e exists and is a character special file.
       --dd _f_i_l_e
              True if _f_i_l_e exists and is a directory.
       --ee _f_i_l_e
              True if _f_i_l_e exists.
       --ff _f_i_l_e
              True if _f_i_l_e exists and is a regular file.
       --gg _f_i_l_e
              True if _f_i_l_e exists and is set-group-id.
       --hh _f_i_l_e
              True if _f_i_l_e exists and is a symbolic link.
       --kk _f_i_l_e
              True if _f_i_l_e exists and its "sticky" bit is set.
       --pp _f_i_l_e
              True if _f_i_l_e exists and is a named pipe (FIFO).
       --rr _f_i_l_e
              True if _f_i_l_e exists and is readable.
       --ss _f_i_l_e
              True if _f_i_l_e exists and has a size greater than zero.
       --tt _f_d  True if file descriptor _f_d is open and refers to a terminal.
       --uu _f_i_l_e
              True if _f_i_l_e exists and its set-user-id bit is set.
       --ww _f_i_l_e
              True if _f_i_l_e exists and is writable.
       --xx _f_i_l_e
              True if _f_i_l_e exists and is executable.
       --GG _f_i_l_e
              True if _f_i_l_e exists and is owned by the effective group id.
       --LL _f_i_l_e
              True if _f_i_l_e exists and is a symbolic link.
       --NN _f_i_l_e
              True if _f_i_l_e exists and has been modified since it was last  ac-
              cessed.
       --OO _f_i_l_e
              True if _f_i_l_e exists and is owned by the effective user id.
       --SS _f_i_l_e
              True if _f_i_l_e exists and is a socket.
       --oo _o_p_t_n_a_m_e
              True  if  the  shell option _o_p_t_n_a_m_e is enabled.  See the list of
              options under the description  of  the  --oo  option  to  the  sseett
              builtin below.
       --vv _v_a_r_n_a_m_e
              True  if  the shell variable _v_a_r_n_a_m_e is set (has been assigned a
              value).  If _v_a_r_n_a_m_e is  an  indexed  array  variable  name  sub-
              scripted  by  _@ or _*, this returns true if the array has any set
              elements.  If _v_a_r_n_a_m_e is an associative array variable name sub-
              scripted by _@ or _*, this returns true if an  element  with  that
              key is set.
       --RR _v_a_r_n_a_m_e
              True  if  the shell variable _v_a_r_n_a_m_e is set and is a name refer-
              ence.
       --zz _s_t_r_i_n_g
              True if the length of _s_t_r_i_n_g is zero.
       _s_t_r_i_n_g
       --nn _s_t_r_i_n_g
              True if the length of _s_t_r_i_n_g is non-zero.

       _s_t_r_i_n_g_1 ==== _s_t_r_i_n_g_2
       _s_t_r_i_n_g_1 == _s_t_r_i_n_g_2
              True if the strings are equal.  == should be used with  the  tteesstt
              command  for  POSIX conformance.  When used with the [[[[ command,
              this performs pattern matching as described above (CCoommppoouunndd CCoomm--
              mmaannddss).
       _s_t_r_i_n_g_1 !!== _s_t_r_i_n_g_2
              True if the strings are not equal.
       _s_t_r_i_n_g_1 << _s_t_r_i_n_g_2
              True if _s_t_r_i_n_g_1 sorts before _s_t_r_i_n_g_2 lexicographically.
       _s_t_r_i_n_g_1 >> _s_t_r_i_n_g_2
              True if _s_t_r_i_n_g_1 sorts after _s_t_r_i_n_g_2 lexicographically.

       _f_i_l_e_1 --eeff _f_i_l_e_2
              True if _f_i_l_e_1 and _f_i_l_e_2 refer to the same device and inode  num-
              bers.
       _f_i_l_e_1 -nntt _f_i_l_e_2
              True  if  _f_i_l_e_1  is  newer (according to modification date) than
              _f_i_l_e_2, or if _f_i_l_e_1 exists and _f_i_l_e_2 does not.
       _f_i_l_e_1 -oott _f_i_l_e_2
              True if _f_i_l_e_1 is older than _f_i_l_e_2, or if _f_i_l_e_2 exists and  _f_i_l_e_1
              does not.

       _a_r_g_1 OOPP _a_r_g_2
              OOPP  is one of --eeqq, --nnee, --lltt, --llee, --ggtt, or --ggee.  These arithmetic
              binary operators return true if _a_r_g_1 is equal to, not equal  to,
              less  than, less than or equal to, greater than, or greater than
              or equal to _a_r_g_2, respectively.  _a_r_g_1 and _a_r_g_2 may  be  positive
              or  negative  integers.  When used with the [[[[ command, _a_r_g_1 and
              _a_r_g_2 are evaluated as  arithmetic  expressions  (see  AARRIITTHHMMEETTIICC
              EEVVAALLUUAATTIIOONN above).  Since the expansions the [[[[ command performs
              on _a_r_g_1 and _a_r_g_2 can potentially result in empty strings, arith-
              metic  expression  evaluation  treats  those as expressions that
              evaluate to 0.

SSIIMMPPLLEE CCOOMMMMAANNDD EEXXPPAANNSSIIOONN
       When the shell executes a simple command, it performs the following ex-
       pansions, assignments, and redirections, from left  to  right,  in  the
       following order.

       1.     The  words  that  the  parser has marked as variable assignments
              (those preceding the command name) and  redirections  are  saved
              for later processing.

       2.     The  words that are not variable assignments or redirections are
              expanded.  If any words remain after expansion, the  first  word
              is  taken  to be the name of the command and the remaining words
              are the arguments.

       3.     Redirections are performed as described above under RREEDDIIRREECCTTIIOONN.

       4.     The text after the == in each variable assignment undergoes tilde
              expansion, parameter expansion, command substitution, arithmetic
              expansion, and quote removal before being assigned to the  vari-
              able.

       If no command name results, the variable assignments affect the current
       shell  environment.   In  the case of such a command (one that consists
       only of assignment statements and redirections), assignment  statements
       are  performed before redirections.  Otherwise, the variables are added
       to the environment of the executed command and do not affect  the  cur-
       rent shell environment.  If any of the assignments attempts to assign a
       value  to  a  readonly variable, an error occurs, and the command exits
       with a non-zero status.

       If no command name results, redirections are performed, but do not  af-
       fect  the  current  shell  environment.  A redirection error causes the
       command to exit with a non-zero status.

       If there is a command name left after expansion, execution proceeds  as
       described  below.   Otherwise, the command exits.  If one of the expan-
       sions contained a command substitution, the exit status of the  command
       is  the  exit  status  of  the last command substitution performed.  If
       there were no command substitutions, the command exits with a zero sta-
       tus.

CCOOMMMMAANNDD EEXXEECCUUTTIIOONN
       After a command has been split into words, if it results  in  a  simple
       command  and an optional list of arguments, the shell performs the fol-
       lowing actions.

       If the command name contains no slashes, the shell attempts  to  locate
       it.   If  there  exists a shell function by that name, that function is
       invoked as described above in FFUUNNCCTTIIOONNSS.  If the name does not match  a
       function,  the shell searches for it in the list of shell builtins.  If
       a match is found, that builtin is invoked.

       If the name is neither a shell function nor a builtin, and contains  no
       slashes,  bbaasshh  searches  each element of the PPAATTHH for a directory con-
       taining an executable file by that name.  BBaasshh uses a hash table to re-
       member the full pathnames of executable files  (see  hhaasshh  under  SSHHEELLLL
       BBUUIILLTTIINN  CCOOMMMMAANNDDSS  below).  Bash performs a full search of the directo-
       ries in PPAATTHH only if the command is not found in the  hash  table.   If
       the  search  is  unsuccessful,  the  shell searches for a defined shell
       function named ccoommmmaanndd__nnoott__ffoouunndd__hhaannddllee.  If that function  exists,  it
       is  invoked  in a separate execution environment with the original com-
       mand and the original command's arguments as  its  arguments,  and  the
       function's  exit  status  becomes the exit status of that subshell.  If
       that function is not defined, the shell prints an error message and re-
       turns an exit status of 127.

       If the search is successful, or if the command  name  contains  one  or
       more slashes, the shell executes the named program in a separate execu-
       tion environment.  Argument 0 is set to the name given, and the remain-
       ing arguments to the command are set to the arguments given, if any.

       If  this  execution fails because the file is not in executable format,
       and the file is not a directory, it is assumed to be a _s_h_e_l_l _s_c_r_i_p_t,  a
       file containing shell commands, and the shell creates a new instance of
       itself  to  execute  it.  Bash tries to determine whether the file is a
       text file or a binary, and will not execute files it determines  to  be
       binaries.  This subshell reinitializes itself, so that the effect is as
       if  a  new shell had been invoked to handle the script, with the excep-
       tion that the locations of commands remembered by the parent (see  hhaasshh
       below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS are retained by the child.

       If  the program is a file beginning with ##!!, the remainder of the first
       line specifies an interpreter for the program.  The shell executes  the
       specified interpreter on operating systems that do not handle this exe-
       cutable format themselves.  The arguments to the interpreter consist of
       a  single optional argument following the interpreter name on the first
       line of the program, followed by the name of the program,  followed  by
       the command arguments, if any.

CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
       The  shell  has an _e_x_e_c_u_t_i_o_n _e_n_v_i_r_o_n_m_e_n_t, which consists of the follow-
       ing:

       +o      Open files inherited by the shell at invocation, as modified  by
              redirections supplied to the eexxeecc builtin.

       +o      The  current  working directory as set by ccdd, ppuusshhdd, or ppooppdd, or
              inherited by the shell at invocation.

       +o      The file creation mode mask as set by uummaasskk  or  inherited  from
              the shell's parent.

       +o      Current traps set by ttrraapp.

       +o      Shell parameters that are set by variable assignment or with sseett
              or inherited from the shell's parent in the environment.

       +o      Shell  functions  defined during execution or inherited from the
              shell's parent in the environment.

       +o      Options enabled at invocation (either by default  or  with  com-
              mand-line arguments) or by sseett.

       +o      Options enabled by sshhoopptt.

       +o      Shell aliases defined with aalliiaass.

       +o      Various  process  IDs,  including  those of background jobs, the
              value of $$$$, and the value of PPPPIIDD.

       When a simple command other than a builtin or shell function is  to  be
       executed,  it  is invoked in a separate execution environment that con-
       sists of the following.  Unless otherwise noted, the values are  inher-
       ited from the shell.

       +o      The  shell's  open  files,  plus any modifications and additions
              specified by redirections to the command.

       +o      The current working directory.

       +o      The file creation mode mask.

       +o      Shell variables and functions  marked  for  export,  along  with
              variables exported for the command, passed in the environment.

       +o      Traps caught by the shell are reset to the values inherited from
              the shell's parent, and traps ignored by the shell are ignored.

       A  command  invoked  in  this  separate  environment  cannot affect the
       shell's execution environment.

       A _s_u_b_s_h_e_l_l is a copy of the shell process.

       Command substitution, commands grouped with parentheses, and  asynchro-
       nous commands are invoked in a subshell environment that is a duplicate
       of the shell environment, except that traps caught by the shell are re-
       set  to  the values that the shell inherited from its parent at invoca-
       tion.  Builtin commands that are invoked as part of a pipeline,  except
       possibly  in  the  last  element depending on the value of the llaassttppiippee
       shell option, are also executed in  a  subshell  environment.   Changes
       made  to  the  subshell environment cannot affect the shell's execution
       environment.

       When the shell is in posix mode, subshells spawned to  execute  command
       substitutions  inherit  the  value  of  the --ee option from their parent
       shell.  When not in posix mode, bbaasshh clears the --ee option in such  sub-
       shells.   See the description of the iinnhheerriitt__eerrrreexxiitt shell option below
       for how to control this behavior when not in posix mode.

       If a command is followed by a && and job control is not active, the  de-
       fault standard input for the command is the empty file _/_d_e_v_/_n_u_l_l.  Oth-
       erwise,  the invoked command inherits the file descriptors of the call-
       ing shell as modified by redirections.

EENNVVIIRROONNMMEENNTT
       When a program is invoked it is given an array of  strings  called  the
       _e_n_v_i_r_o_n_m_e_n_t.   This  is  a  list  of  _n_a_m_e-_v_a_l_u_e  pairs,  of  the  form
       _n_a_m_e=_v_a_l_u_e.

       The shell provides several ways to manipulate the environment.  On  in-
       vocation,  the  shell scans its own environment and creates a parameter
       for each name found, automatically  marking  it  for  _e_x_p_o_r_t  to  child
       processes.  Executed commands inherit the environment.  The eexxppoorrtt, ddee--
       ccllaarree  --xx,  and  uunnsseett  commands  modify  the environment by adding and
       deleting parameters and functions.  If the value of a parameter in  the
       environment  is  modified,  the new value automatically becomes part of
       the environment, replacing the old.  The environment inherited  by  any
       executed  command  consists  of  the shell's initial environment, whose
       values may be modified in the shell, less any pairs removed by the  uunn--
       sseett  or  eexxppoorrtt  --nn commands, plus any additions via the eexxppoorrtt and ddee--
       ccllaarree --xx commands.

       If any parameter assignments, as described above in PPAARRAAMMEETTEERRSS,  appear
       before a _s_i_m_p_l_e _c_o_m_m_a_n_d, the variable assignments are part of that com-
       mand's environment for as long as it executes.  These assignment state-
       ments  affect  only the environment seen by that command.  If these as-
       signments precede a call to a shell function, the variables  are  local
       to the function and exported to that function's children.

       If  the  --kk option is set (see the sseett builtin command below), then _a_l_l
       parameter assignments are placed in the environment for a command,  not
       just those that precede the command name.

       When  bbaasshh  invokes  an  external command, the variable __ is set to the
       full pathname of the command and passed to that command in its environ-
       ment.

EEXXIITT SSTTAATTUUSS
       The exit status of an executed command is the  value  returned  by  the
       _w_a_i_t_p_i_d system call or equivalent function.  Exit statuses fall between
       0  and  255, though, as explained below, the shell may use values above
       125 specially.  Exit statuses from shell builtins and compound commands
       are also limited to this range.  Under certain circumstances, the shell
       will use special values to indicate specific failure modes.

       For the shell's purposes, a command which exits with a zero exit status
       has succeeded.  So while an exit status of zero  indicates  success,  a
       non-zero exit status indicates failure.

       When  a  command terminates on a fatal signal _N, bbaasshh uses the value of
       128+_N as the exit status.

       If a command is not found, the child process created to execute it  re-
       turns  a  status  of 127.  If a command is found but is not executable,
       the return status is 126.

       If a command fails because of an error during expansion or redirection,
       the exit status is greater than zero.

       Shell builtin commands return a status of 0 (_t_r_u_e) if  successful,  and
       non-zero  (_f_a_l_s_e)  if an error occurs while they execute.  All builtins
       return an exit status of 2 to indicate incorrect usage,  generally  in-
       valid options or missing arguments.

       The exit status of the last command is available in the special parame-
       ter $?.

       BBaasshh  itself  returns the exit status of the last command executed, un-
       less a syntax error occurs, in which case  it  exits  with  a  non-zero
       value.  See also the eexxiitt builtin command below.

SSIIGGNNAALLSS
       When  bbaasshh  is  interactive,  in  the  absence of any traps, it ignores
       SSIIGGTTEERRMM (so that kkiillll 00  does  not  kill  an  interactive  shell),  and
       catches and handles SSIIGGIINNTT (so that the wwaaiitt builtin is interruptible).
       When  bbaasshh  receives  SSIIGGIINNTT, it breaks out of any executing loops.  In
       all cases, bbaasshh ignores SSIIGGQQUUIITT.  If job control is in effect, bbaasshh ig-
       nores SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP.

       The ttrraapp builtin modifies the shell's signal handling, as described be-
       low.

       Non-builtin commands bbaasshh executes have signal handlers set to the val-
       ues inherited by the shell from its parent, unless ttrraapp sets them to be
       ignored, in which case the child process  will  ignore  them  as  well.
       When  job control is not in effect, asynchronous commands ignore SSIIGGIINNTT
       and SSIIGGQQUUIITT in addition to these inherited handlers.  Commands run as a
       result of command substitution ignore the keyboard-generated  job  con-
       trol signals SSIIGGTTTTIINN, SSIIGGTTTTOOUU, and SSIIGGTTSSTTPP.

       The  shell  exits by default upon receipt of a SSIIGGHHUUPP.  Before exiting,
       an interactive shell  resends  the  SSIIGGHHUUPP  to  all  jobs,  running  or
       stopped.   The  shell sends SSIIGGCCOONNTT to stopped jobs to ensure that they
       receive the SSIIGGHHUUPP (see JJOOBB CCOONNTTRROOLL below for  more  information  about
       running  and stopped jobs).  To prevent the shell from sending the sig-
       nal to a particular job, remove it from the jobs table with the  ddiissoowwnn
       builtin  (see  SSHHEELLLL  BBUUIILLTTIINN CCOOMMMMAANNDDSS below) or mark it not to receive
       SSIIGGHHUUPP using ddiissoowwnn --hh.

       If the hhuuppoonneexxiitt shell option has been set using sshhoopptt,  bbaasshh  sends  a
       SSIIGGHHUUPP to all jobs when an interactive login shell exits.

       If  bbaasshh is waiting for a command to complete and receives a signal for
       which a trap has been set, it will not execute the trap until the  com-
       mand completes.  If bbaasshh is waiting for an asynchronous command via the
       wwaaiitt  builtin,  and it receives a signal for which a trap has been set,
       the wwaaiitt builtin will return immediately with an  exit  status  greater
       than 128, immediately after which the shell executes the trap.

       When  job  control is not enabled, and bbaasshh is waiting for a foreground
       command to complete, the shell receives keyboard-generated signals such
       as SSIIGGIINNTT (usually generated by ^^CC) that users commonly intend to  send
       to that command.  This happens because the shell and the command are in
       the  same  process  group  as  the terminal, and ^^CC sends SSIIGGIINNTT to all
       processes in that process group.  Since bbaasshh does not enable  job  con-
       trol  by  default  when  the shell is not interactive, this scenario is
       most common in non-interactive shells.

       When job control is enabled, and bbaasshh is waiting for a foreground  com-
       mand  to  complete,  the shell does not receive keyboard-generated sig-
       nals, because it is not in the same  process  group  as  the  terminal.
       This scenario is most common in interactive shells, where bbaasshh attempts
       to  enable  job control by default.  See JJOOBB CCOONNTTRROOLL below for more in-
       formation about process groups.

       When job control is not enabled, and bbaasshh receives SSIIGGIINNTT while waiting
       for a foreground command, it waits until that foreground command termi-
       nates and then decides what to do about the SSIIGGIINNTT:

       1.     If the command terminates due to the SSIIGGIINNTT, bbaasshh concludes that
              the user meant to send the SSIIGGIINNTT to the shell as well, and acts
              on the SSIIGGIINNTT (e.g., by running a SSIIGGIINNTT trap, exiting a non-in-
              teractive shell, or returning to the top level  to  read  a  new
              command).

       2.     If  the  command  does  not terminate due to SSIIGGIINNTT, the program
              handled the SSIIGGIINNTT itself and did not treat it as a  fatal  sig-
              nal.   In  that case, bbaasshh does not treat SSIIGGIINNTT as a fatal sig-
              nal, either, instead assuming that the SSIIGGIINNTT was used  as  part
              of  the program's normal operation (e.g., emacs uses it to abort
              editing commands) or deliberately discarded.  However, bbaasshh will
              run any trap set on SSIIGGIINNTT, as it does with  any  other  trapped
              signal  it  receives while it is waiting for the foreground com-
              mand to complete, for compatibility.

       When job control is enabled, bbaasshh does not  receive  keyboard-generated
       signals  such  as  SSIIGGIINNTT while it is waiting for a foreground command.
       An interactive shell does not pay attention to the SSIIGGIINNTT, even if  the
       foreground  command  terminates as a result, other than noting its exit
       status.  If the shell is not interactive, and  the  foreground  command
       terminates  due to the SSIIGGIINNTT, bbaasshh pretends it received the SSIIGGIINNTT it-
       self (scenario 1 above), for compatibility.

JJOOBB CCOONNTTRROOLL
       _J_o_b _c_o_n_t_r_o_l refers to the ability to selectively stop (_s_u_s_p_e_n_d) the ex-
       ecution of processes and continue (_r_e_s_u_m_e) their execution at  a  later
       point.   A  user typically employs this facility via an interactive in-
       terface supplied jointly by the operating system kernel's terminal dri-
       ver and bbaasshh.

       The shell associates a _j_o_b with each pipeline.  It  keeps  a  table  of
       currently  executing  jobs,  which the jjoobbss command will display.  Each
       job has a _j_o_b _n_u_m_b_e_r, which jjoobbss displays between brackets.   Job  num-
       bers  start  at 1.  When bbaasshh starts a job asynchronously (in the _b_a_c_k_-
       _g_r_o_u_n_d), it prints a line that looks like:

              [1] 25647

       indicating that this job is job number 1 and that the process ID of the
       last process in the pipeline associated with this job is 25647.  All of
       the processes in a single pipeline are members of the same  job.   BBaasshh
       uses the _j_o_b abstraction as the basis for job control.

       To  facilitate the implementation of the user interface to job control,
       each process has a _p_r_o_c_e_s_s _g_r_o_u_p _I_D, and the operating system maintains
       the notion of a _c_u_r_r_e_n_t  _t_e_r_m_i_n_a_l  _p_r_o_c_e_s_s  _g_r_o_u_p  _I_D.   This  terminal
       process group ID is associated with the _c_o_n_t_r_o_l_l_i_n_g _t_e_r_m_i_n_a_l.

       Processes  that  have  the same process group ID are said to be part of
       the same _p_r_o_c_e_s_s  _g_r_o_u_p.   Members  of  the  _f_o_r_e_g_r_o_u_n_d  process  group
       (processes  whose  process  group  ID  is equal to the current terminal
       process group ID) receive keyboard-generated signals  such  as  SSIIGGIINNTT.
       Processes  in  the  foreground  process group are said to be _f_o_r_e_g_r_o_u_n_d
       processes.  _B_a_c_k_g_r_o_u_n_d processes are those whose process group ID  dif-
       fers from the controlling terminal's; such processes are immune to key-
       board-generated signals.  Only foreground processes are allowed to read
       from or, if the user so specifies with "stty tostop", write to the con-
       trolling  terminal.   The  system  sends  a SSIIGGTTTTIINN ((SSIIGGTTTTOOUU)) signal to
       background processes which attempt to read from (write to when "tostop"
       is in effect) the terminal, which, unless caught, suspends the process.

       If the operating system on which bbaasshh is running supports job  control,
       bbaasshh contains facilities to use it.  Typing the _s_u_s_p_e_n_d character (typ-
       ically ^^ZZ, Control-Z) while a process is running stops that process and
       returns  control  to bbaasshh.  Typing the _d_e_l_a_y_e_d _s_u_s_p_e_n_d character (typi-
       cally ^^YY, Control-Y) causes the process stop when it attempts  to  read
       input  from  the  terminal, and returns control to bbaasshh.  The user then
       manipulates the state of this job, using the bbgg command to continue  it
       in  the background, the ffgg command to continue it in the foreground, or
       the kkiillll command to kill it.  The suspend character takes effect  imme-
       diately,  and  has the additional side effect of discarding any pending
       output and typeahead.  To force a background process to stop, or stop a
       process that's not associated with the current terminal  session,  send
       it the SSIIGGSSTTOOPP signal using kkiillll.

       There are a number of ways to refer to a job in the shell.  The %% char-
       acter introduces a job specification (jobspec).

       Job  number  _n may be referred to as %%nn.  A job may also be referred to
       using a prefix of the name used to start it, or using a substring  that
       appears  in  its  command line.  For example, %%ccee refers to a job whose
       command name begins with ccee.  Using %%??ccee, on the other hand, refers  to
       any job containing the string ccee in its command line.  If the prefix or
       substring matches more than one job, bbaasshh reports an error.

       The  symbols  %%%% and %%++ refer to the shell's notion of the _c_u_r_r_e_n_t _j_o_b.
       A single % (with no accompanying job specification) also refers to  the
       current  job.  %%-- refers to the _p_r_e_v_i_o_u_s _j_o_b.  When a job starts in the
       background, a job stops while in the foreground, or a job is resumed in
       the background, it becomes the current job.  The job that was the  cur-
       rent  job  becomes  the previous job.  When the current job terminates,
       the previous job becomes the current job.  If there is  only  a  single
       job,  %%++  and %%-- can both be used to refer to that job.  In output per-
       taining to jobs (e.g., the output of the jjoobbss command), the current job
       is always marked with a ++, and the previous job with a --.

       Simply naming a job can be used to bring it into the foreground: %%11  is
       a  synonym  for  "fg  %1",  bringing job 1 from the background into the
       foreground.  Similarly, "%1 &" resumes job 1 in the background, equiva-
       lent to "bg %1".

       The shell learns immediately whenever a job changes  state.   Normally,
       bbaasshh  waits  until  it  is about to print a prompt before notifying the
       user about changes in a job's status so as to not interrupt  any  other
       output,  though  it  will  notify  of changes in a job's status after a
       foreground command in a list completes, before executing the next  com-
       mand  in  the list.  If the --bb option to the sseett builtin command is en-
       abled, bbaasshh reports status changes immediately.  BBaasshh executes any trap
       on SSIIGGCCHHLLDD for each child that terminates.

       When a job terminates and bbaasshh notifies the user about it, bbaasshh removes
       the job from the table.  It will not appear in jjoobbss  output,  but  wwaaiitt
       will  report  its  exit status, as long as it's supplied the process ID
       associated with the job as an argument.  When the table is  empty,  job
       numbers start over at 1.

       If  a  user  attempts  to  exit bbaasshh while jobs are stopped (or, if the
       cchheecckkjjoobbss shell option has been enabled using the sshhoopptt  builtin,  run-
       ning), the shell prints a warning message, and, if the cchheecckkjjoobbss option
       is  enabled,  lists  the jobs and their statuses.  The jjoobbss command may
       then be used to inspect their status.  If the user immediately attempts
       to exit again, without an intervening command, bbaasshh does not print  an-
       other warning, and terminates any stopped jobs.

       When  the shell is waiting for a job or process using the wwaaiitt builtin,
       and job control is enabled, wwaaiitt  will  return  when  the  job  changes
       state.  The --ff option causes wwaaiitt to wait until the job or process ter-
       minates before returning.

PPRROOMMPPTTIINNGG
       When executing interactively, bbaasshh displays the primary prompt PPSS11 when
       it  is  ready  to  read a command, and the secondary prompt PPSS22 when it
       needs more input to complete a command.

       BBaasshh examines the value of the array variable PPRROOMMPPTT__CCOOMMMMAANNDD  just  be-
       fore  printing  each primary prompt.  If any elements in PPRROOMMPPTT__CCOOMMMMAANNDD
       are set and non-null, Bash executes each value, in numeric order,  just
       as  if  it had been typed on the command line.  BBaasshh displays PPSS00 after
       it reads a command but before executing it.

       BBaasshh displays PPSS44 as described above before tracing each  command  when
       the --xx option is enabled.

       BBaasshh allows the prompt strings PPSS00, PPSS11, PPSS22, and PPSS44, to be customized
       by  inserting a number of backslash-escaped special characters that are
       decoded as follows:

              \\aa     An ASCII bell character (07).
              \\dd     The date in "Weekday Month Date" format (e.g.,  "Tue  May
                     26").
              \\DD{{_f_o_r_m_a_t}}
                     The _f_o_r_m_a_t is passed to _s_t_r_f_t_i_m_e(3) and the result is in-
                     serted into the prompt string; an empty _f_o_r_m_a_t results in
                     a  locale-specific  time  representation.  The braces are
                     required.
              \\ee     An ASCII escape character (033).
              \\hh     The hostname up to the first ".".
              \\HH     The hostname.
              \\jj     The number of jobs currently managed by the shell.
              \\ll     The basename of the shell's terminal device  name  (e.g.,
                     "ttys0").
              \\nn     A newline.
              \\rr     A carriage return.
              \\ss     The  name  of  the shell: the basename of $$00 (the portion
                     following the final slash).
              \\tt     The current time in 24-hour HH:MM:SS format.
              \\TT     The current time in 12-hour HH:MM:SS format.
              \\@@     The current time in 12-hour am/pm format.
              \\AA     The current time in 24-hour HH:MM format.
              \\uu     The username of the current user.
              \\vv     The bbaasshh version (e.g., 2.00).
              \\VV     The bbaasshh release, version + patch level (e.g., 2.00.0)
              \\ww     The value of the PPWWDD shell variable  ($$PPWWDD),  with  $$HHOOMMEE
                     abbreviated   with   a  tilde  (uses  the  value  of  the
                     PPRROOMMPPTT__DDIIRRTTRRIIMM variable).
              \\WW     The basename of  $$PPWWDD,  with  $$HHOOMMEE  abbreviated  with  a
                     tilde.
              \\!!     The history number of this command.
              \\##     The command number of this command.
              \\$$     If the effective UID is 0, a ##, otherwise a $$.
              \\_n_n_n   The character corresponding to the octal number _n_n_n.
              \\\\     A backslash.
              \\[[     Begin  a sequence of non-printing characters, which could
                     be used to embed a terminal  control  sequence  into  the
                     prompt.
              \\]]     End a sequence of non-printing characters.

       The  command  number  and the history number are usually different: the
       history number of a command is its position in the history list,  which
       may  include  commands  restored from the history file (see HHIISSTTOORRYY be-
       low), while the command number is the position in the sequence of  com-
       mands  executed  during the current shell session.  After the string is
       decoded, it is expanded via parameter expansion, command  substitution,
       arithmetic  expansion,  and  quote removal, subject to the value of the
       pprroommppttvvaarrss shell option (see the description of the sshhoopptt command under
       SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  This can have unwanted side effects  if
       escaped  portions  of  the string appear within command substitution or
       contain characters special to word expansion.

RREEAADDLLIINNEE
       This is the library that handles reading input when using  an  interac-
       tive  shell, unless the ----nnooeeddiittiinngg option is supplied at shell invoca-
       tion.  Line editing is also used when using the --ee option to  the  rreeaadd
       builtin.  By default, the line editing commands are similar to those of
       emacs; a vi-style line editing interface is also available.  Line edit-
       ing  can  be enabled at any time using the --oo eemmaaccss or --oo vvii options to
       the sseett builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  To turn  off  line
       editing  after  the shell is running, use the ++oo eemmaaccss or ++oo vvii options
       to the sseett builtin.

   RReeaaddlliinnee NNoottaattiioonn
       This section uses Emacs-style editing concepts and  uses  its  notation
       for  keystrokes.   Control  keys  are denoted by C-_k_e_y, e.g., C-n means
       Control-N.  Similarly, _m_e_t_a keys are denoted by  M-_k_e_y,  so  M-x  means
       Meta-X.  The Meta key is often labeled "Alt" or "Option".

       On  keyboards  without a _M_e_t_a key, M-_x means ESC _x, i.e., press and re-
       lease the Escape key, then press and release the _x  key,  in  sequence.
       This  makes  ESC the _m_e_t_a _p_r_e_f_i_x.  The combination M-C-_x means ESC Con-
       trol-_x: press and release the Escape key, then press and hold the  Con-
       trol key while pressing the _x key, then release both.

       On  some  keyboards, the Meta key modifier produces characters with the
       eighth bit (0200) set.  You can use  the  eennaabbllee--mmeettaa--kkeeyy  variable  to
       control  whether  or  not  it does this, if the keyboard allows it.  On
       many others, the terminal or terminal emulator  converts  the  metafied
       key  to a key sequence beginning with ESC as described in the preceding
       paragraph.

       If your _M_e_t_a key produces a key sequence with the ESC meta prefix,  you
       can  make M-_k_e_y key bindings you specify (see RReeaaddlliinnee KKeeyy BBiinnddiinnggss be-
       low) do the same thing by setting the ffoorrccee--mmeettaa--pprreeffiixx variable.

       RReeaaddlliinnee commands may be given numeric _a_r_g_u_m_e_n_t_s, which normally act as
       a repeat count.  Sometimes, however, it is the  sign  of  the  argument
       that  is  significant.   Passing  a negative argument to a command that
       acts in the forward direction (e.g., kkiillll--lliinnee) makes that command  act
       in  a backward direction.  Commands whose behavior with arguments devi-
       ates from this are noted below.

       The _p_o_i_n_t is the current cursor position, and _m_a_r_k refers  to  a  saved
       cursor position.  The text between the point and mark is referred to as
       the _r_e_g_i_o_n.  RReeaaddlliinnee has the concept of an _a_c_t_i_v_e _r_e_g_i_o_n: when the re-
       gion  is  active,  rreeaaddlliinnee  redisplay  highlights the region using the
       value of the aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr variable.  The eennaabbllee--aaccttiivvee--rree--
       ggiioonn variable turns this on and off.  Several commands set  the  region
       to active; those are noted below.

       When  a command is described as _k_i_l_l_i_n_g text, the text deleted is saved
       for possible future retrieval (_y_a_n_k_i_n_g).  The killed text is saved in a
       _k_i_l_l _r_i_n_g.  Consecutive kills accumulate  the  deleted  text  into  one
       unit, which can be yanked all at once.  Commands which do not kill text
       separate the chunks of text on the kill ring.

   RReeaaddlliinnee IInniittiiaalliizzaattiioonn
       RReeaaddlliinnee  is  customized  by putting commands in an initialization file
       (the _i_n_p_u_t_r_c file).  The name of this file is taken from the  value  of
       the  IINNPPUUTTRRCC shell variable.  If that variable is unset, the default is
       _~_/_._i_n_p_u_t_r_c.  If that file  does not exist or cannot be  read,  rreeaaddlliinnee
       looks  for _/_e_t_c_/_i_n_p_u_t_r_c.  When a program that uses the rreeaaddlliinnee library
       starts up, rreeaaddlliinnee reads the initialization  file  and  sets  the  key
       bindings and variables found there, before reading any user input.

       There  are  only  a  few  basic constructs allowed in the inputrc file.
       Blank lines are ignored.  Lines beginning with a ## are comments.  Lines
       beginning with a $$ indicate conditional constructs.  Other lines denote
       key bindings and variable settings.

       The default key-bindings in this section may be changed using key bind-
       ing commands in the _i_n_p_u_t_r_c file.  Programs that use the  rreeaaddlliinnee  li-
       brary, including bbaasshh, may add their own commands and bindings.

       For example, placing

              M-Control-u: universal-argument
       or
              C-Meta-u: universal-argument

       into  the _i_n_p_u_t_r_c would make M-C-u execute the rreeaaddlliinnee command _u_n_i_v_e_r_-
       _s_a_l_-_a_r_g_u_m_e_n_t.

       Key bindings may contain the following symbolic character  names:  _D_E_L,
       _E_S_C,  _E_S_C_A_P_E,  _L_F_D,  _N_E_W_L_I_N_E,  _R_E_T, _R_E_T_U_R_N, _R_U_B_O_U_T (a destructive back-
       space), _S_P_A_C_E, _S_P_C, and _T_A_B.

       In addition to command names, rreeaaddlliinnee allows keys to  be  bound  to  a
       string that is inserted when the key is pressed (a _m_a_c_r_o).  The differ-
       ence  between a macro and a command is that a macro is enclosed in sin-
       gle or double quotes.

   RReeaaddlliinnee KKeeyy BBiinnddiinnggss
       The syntax for controlling key bindings in the _i_n_p_u_t_r_c file is  simple.
       All  that is required is the name of the command or the text of a macro
       and a key sequence to which it should be bound.  The key  sequence  may
       be  specified in one of two ways: as a symbolic key name, possibly with
       _M_e_t_a_- or _C_o_n_t_r_o_l_- prefixes, or as a key sequence  composed  of  one  or
       more  characters  enclosed in double quotes.  The key sequence and name
       are separated by a colon.  There can be no whitespace between the  name
       and the colon.

       When using the form kkeeyynnaammee:_f_u_n_c_t_i_o_n_-_n_a_m_e or _m_a_c_r_o, _k_e_y_n_a_m_e is the name
       of a key spelled out in English.  For example:

              Control-u: universal-argument
              Meta-Rubout: backward-kill-word
              Control-o: "> output"

       In  the above example, _C_-_u is bound to the function uunniivveerrssaall--aarrgguummeenntt,
       _M_-_D_E_L is bound to the function bbaacckkwwaarrdd--kkiillll--wwoorrdd, and _C_-_o is bound  to
       run  the macro expressed on the right hand side (that is, to insert the
       text "> output" into the line).

       In the second form, ""kkeeyysseeqq"":_f_u_n_c_t_i_o_n_-_n_a_m_e  or  _m_a_c_r_o,  kkeeyysseeqq  differs
       from  kkeeyynnaammee above in that strings denoting an entire key sequence may
       be specified by placing the sequence within double  quotes.   Some  GNU
       Emacs  style  key escapes can be used, as in the following example, but
       none of the symbolic character names are recognized.

              "\C-u": universal-argument
              "\C-x\C-r": re-read-init-file
              "\e[11~": "Function Key 1"

       In this example, _C_-_u is again bound to the function uunniivveerrssaall--aarrgguummeenntt.
       _C_-_x _C_-_r is bound to the function rree--rreeaadd--iinniitt--ffiillee, and _E_S_C _[ _1 _1 _~  is
       bound to insert the text "Function Key 1".

       The  full set of GNU Emacs style escape sequences available when speci-
       fying key sequences is
              \\CC--    A control prefix.
              \\MM--    Adding the meta prefix or converting the following  char-
                     acter  to  a  meta  character,  as  described below under
                     ffoorrccee--mmeettaa--pprreeffiixx.
              \\ee     An escape character.
              \\\\     Backslash.
              \\""     Literal ", a double quote.
              \\''     Literal ', a single quote.

       In addition to the GNU Emacs style escape sequences, a  second  set  of
       backslash escapes is available:
              \\aa     alert (bell)
              \\bb     backspace
              \\dd     delete
              \\ff     form feed
              \\nn     newline
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\_n_n_n   The  eight-bit  character  whose value is the octal value
                     _n_n_n (one to three digits).
              \\xx_H_H   The eight-bit character whose value  is  the  hexadecimal
                     value _H_H (one or two hex digits).

       When entering the text of a macro, single or double quotes must be used
       to indicate a macro definition.  Unquoted text is assumed to be a func-
       tion  name.   The backslash escapes described above are expanded in the
       macro body.  Backslash quotes any other character in  the  macro  text,
       including " and '.

       BBaasshh  will display or modify the current rreeaaddlliinnee key bindings with the
       bbiinndd builtin command.  The --oo eemmaaccss or --oo vvii options to the sseett builtin
       (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) change the editing mode  during  in-
       teractive use.

   RReeaaddlliinnee VVaarriiaabblleess
       RReeaaddlliinnee has variables that can be used to further customize its behav-
       ior.  A variable may be set in the _i_n_p_u_t_r_c file with a statement of the
       form

              sseett _v_a_r_i_a_b_l_e_-_n_a_m_e _v_a_l_u_e
       or using the bbiinndd builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       Except  where  noted,  rreeaaddlliinnee variables can take the values OOnn or OOffff
       (without regard to case).  Unrecognized  variable  names  are  ignored.
       When rreeaaddlliinnee reads a variable value, empty or null values, "on" (case-
       insensitive),  and  "1"  are  equivalent  to  OOnn.  All other values are
       equivalent to OOffff.

       The bbiinndd --VV command lists the current rreeaaddlliinnee variable names and  val-
       ues (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below).

       The variables and their default values are:

       aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr
              A  string  variable  that controls the text color and background
              when displaying the text in the active region (see the  descrip-
              tion  of eennaabbllee--aaccttiivvee--rreeggiioonn below).  This string must not take
              up any physical character positions on the display, so it should
              consist only of terminal escape sequences.  It is output to  the
              terminal  before displaying the text in the active region.  This
              variable is reset to the default  value  whenever  the  terminal
              type  changes.   The  default  value is the string that puts the
              terminal in standout mode, as obtained from the terminal's  ter-
              minfo description.  A sample value might be "\e[01;33m".
       aaccttiivvee--rreeggiioonn--eenndd--ccoolloorr
              A  string  variable  that  "undoes"  the  effects  of aaccttiivvee--rree--
              ggiioonn--ssttaarrtt--ccoolloorr and restores "normal" terminal display  appear-
              ance  after  displaying  text in the active region.  This string
              must not take up any physical character positions  on  the  dis-
              play,  so  it  should consist only of terminal escape sequences.
              It is output to the terminal after displaying the  text  in  the
              active  region.   This  variable  is  reset to the default value
              whenever the terminal type changes.  The default  value  is  the
              string  that  restores  the  terminal from standout mode, as ob-
              tained from the terminal's terminfo description.  A sample value
              might be "\e[0m".
       bbeellll--ssttyyllee ((aauuddiibbllee))
              Controls what happens when rreeaaddlliinnee wants to ring  the  terminal
              bell.  If set to nnoonnee, rreeaaddlliinnee never rings the bell.  If set to
              vviissiibbllee,  rreeaaddlliinnee  uses a visible bell if one is available.  If
              set to aauuddiibbllee, rreeaaddlliinnee attempts to ring the terminal's bell.
       bbiinndd--ttttyy--ssppeecciiaall--cchhaarrss ((OOnn))
              If set to OOnn, rreeaaddlliinnee attempts to bind the  control  characters
              that  are  treated  specially by the kernel's terminal driver to
              their rreeaaddlliinnee equivalents.  These override the default rreeaaddlliinnee
              bindings described here.  Type "stty -a" at a bbaasshh prompt to see
              your current terminal settings, including  the  special  control
              characters (usually cccchhaarrss).
       bblliinnkk--mmaattcchhiinngg--ppaarreenn ((OOffff))
              If set to OOnn, rreeaaddlliinnee attempts to briefly move the cursor to an
              opening parenthesis when a closing parenthesis is inserted.
       ccoolloorreedd--ccoommpplleettiioonn--pprreeffiixx ((OOffff))
              If  set  to  OOnn, when listing completions, rreeaaddlliinnee displays the
              common prefix of the set of possible completions using a differ-
              ent color.  The color definitions are taken from  the  value  of
              the LLSS__CCOOLLOORRSS environment variable.  If there is a color defini-
              tion in $$LLSS__CCOOLLOORRSS for the custom suffix ".readline-colored-com-
              pletion-prefix",  rreeaaddlliinnee uses this color for the common prefix
              instead of its default.
       ccoolloorreedd--ssttaattss ((OOffff))
              If set to OOnn, rreeaaddlliinnee displays possible completions using  dif-
              ferent  colors  to  indicate their file type.  The color defini-
              tions are taken from the  value  of  the  LLSS__CCOOLLOORRSS  environment
              variable.
       ccoommmmeenntt--bbeeggiinn (("##"))
              The  string  that  the  rreeaaddlliinnee iinnsseerrtt--ccoommmmeenntt command inserts.
              This command is bound to MM--## in emacs mode and to ## in  vi  com-
              mand mode.
       ccoommpplleettiioonn--ddiissppllaayy--wwiiddtthh ((--11))
              The  number  of  screen columns used to display possible matches
              when performing completion.  The value is ignored if it is  less
              than  0 or greater than the terminal screen width.  A value of 0
              causes matches to be displayed one per line.  The default  value
              is -1.
       ccoommpplleettiioonn--iiggnnoorree--ccaassee ((OOffff))
              If set to OOnn, rreeaaddlliinnee performs filename matching and completion
              in a case-insensitive fashion.
       ccoommpplleettiioonn--mmaapp--ccaassee ((OOffff))
              If  set  to  OOnn, and ccoommpplleettiioonn--iiggnnoorree--ccaassee is enabled, rreeaaddlliinnee
              treats hyphens (_-) and underscores (__) as equivalent  when  per-
              forming case-insensitive filename matching and completion.
       ccoommpplleettiioonn--pprreeffiixx--ddiissppllaayy--lleennggtthh ((00))
              The  maximum length in characters of the common prefix of a list
              of possible completions that is displayed without  modification.
              When  set to a value greater than zero, rreeaaddlliinnee replaces common
              prefixes longer than this value with an ellipsis when displaying
              possible completions.  If a completion begins with a period, and
              eeaaddlliinnee is completing filenames, it uses three  underscores  in-
              stead of an ellipsis.
       ccoommpplleettiioonn--qquueerryy--iitteemmss ((110000))
              This  determines when the user is queried about viewing the num-
              ber of possible completions generated  by  the  ppoossssiibbllee--ccoommppllee--
              ttiioonnss  command.  It may be set to any integer value greater than
              or equal to zero.  If the  number  of  possible  completions  is
              greater  than  or  equal to the value of this variable, rreeaaddlliinnee
              asks whether or not the user  wishes  to  view  them;  otherwise
              rreeaaddlliinnee  simply lists them on the terminal.  A zero value means
              rreeaaddlliinnee should never ask; negative values are treated as zero.
       ccoonnvveerrtt--mmeettaa ((OOnn))
              If set to OOnn, rreeaaddlliinnee converts characters it  reads  that  have
              the  eighth  bit  set  to  an ASCII key sequence by clearing the
              eighth bit and prefixing it with an escape character (converting
              the character to have the meta prefix).  The default is _O_n,  but
              rreeaaddlliinnee  sets it to _O_f_f if the locale contains characters whose
              encodings may include bytes with the eighth bit set.  This vari-
              able is dependent on  the  LLCC__CCTTYYPPEE  locale  category,  and  may
              change  if  the  locale changes.  This variable also affects key
              bindings; see the description of ffoorrccee--mmeettaa--pprreeffiixx below.
       ddiissaabbllee--ccoommpplleettiioonn ((OOffff))
              If set to OOnn, rreeaaddlliinnee  inhibits  word  completion.   Completion
              characters are inserted into the line as if they had been mapped
              to sseellff--iinnsseerrtt.
       eecchhoo--ccoonnttrrooll--cchhaarraacctteerrss ((OOnn))
              When  set to OOnn, on operating systems that indicate they support
              it, rreeaaddlliinnee echoes a character corresponding to a signal gener-
              ated from the keyboard.
       eeddiittiinngg--mmooddee ((eemmaaccss))
              Controls whether rreeaaddlliinnee uses a set of key bindings similar  to
              _E_m_a_c_s or _v_i.  eeddiittiinngg--mmooddee can be set to either eemmaaccss or vvii.
       eemmaaccss--mmooddee--ssttrriinngg ((@@))
              If  the  _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this string is
              displayed immediately before the last line of the primary prompt
              when emacs editing mode is active.  The value is expanded like a
              key binding, so the standard set of meta- and control-  prefixes
              and  backslash escape sequences is available.  The \1 and \2 es-
              capes begin and end sequences of non-printing characters,  which
              can  be  used to embed a terminal control sequence into the mode
              string.
       eennaabbllee--aaccttiivvee--rreeggiioonn ((OOnn))
              When this variable is set to _O_n, rreeaaddlliinnee  allows  certain  com-
              mands to designate the region as _a_c_t_i_v_e.  When the region is ac-
              tive, rreeaaddlliinnee highlights the text in the region using the value
              of the aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr variable, which defaults to the
              string  that  enables  the terminal's standout mode.  The active
              region shows the text inserted by bracketed-paste and any match-
              ing  text  found  by  incremental  and  non-incremental  history
              searches.
       eennaabbllee--bbrraacckkeetteedd--ppaassttee ((OOnn))
              When  set to OOnn, rreeaaddlliinnee configures the terminal to insert each
              paste into the editing buffer as a single string of  characters,
              instead  of  treating each character as if it had been read from
              the keyboard.  This is called _b_r_a_c_k_e_t_e_d_-_p_a_s_t_e _m_o_d_e; it  prevents
              rreeaaddlliinnee  from  executing  any editing commands bound to key se-
              quences appearing in the pasted text.
       eennaabbllee--kkeeyyppaadd ((OOffff))
              When set to OOnn, rreeaaddlliinnee tries  to enable the application keypad
              when it is called.  Some systems need this to enable  the  arrow
              keys.
       eennaabbllee--mmeettaa--kkeeyy ((OOnn))
              When  set  to OOnn, rreeaaddlliinnee tries to enable any meta modifier key
              the terminal claims to support.  On many terminals, the Meta key
              is used to send eight-bit characters; this variable  checks  for
              the  terminal  capability that indicates the terminal can enable
              and disable a mode that sets  the  eighth  bit  of  a  character
              (0200)  if the Meta key is held down when the character is typed
              (a meta character).
       eexxppaanndd--ttiillddee ((OOffff))
              If set to OOnn, rreeaaddlliinnee performs tilde expansion when it attempts
              word completion.
       ffoorrccee--mmeettaa--pprreeffiixx ((OOffff))
              If set to OOnn, rreeaaddlliinnee modifies its behavior  when  binding  key
              sequences  containing  \M-  or Meta- (see KKeeyy BBiinnddiinnggss above) by
              converting a key sequence of the form \M-_C or Meta-_C to the two-
              character  sequence  EESSCC  _C  (adding  the  meta   prefix).    If
              ffoorrccee--mmeettaa--pprreeffiixx is set to OOffff (the default), rreeaaddlliinnee uses the
              value  of the ccoonnvveerrtt--mmeettaa variable to determine whether to per-
              form this conversion: if ccoonnvveerrtt--mmeettaa is OOnn,  rreeaaddlliinnee  performs
              the  conversion described above; if it is OOffff, rreeaaddlliinnee converts
              _C to a meta character by setting the eighth bit (0200).
       hhiissttoorryy--pprreesseerrvvee--ppooiinntt ((OOffff))
              If set to OOnn, the history code attempts to place  point  at  the
              same  location on each history line retrieved with pprreevviioouuss--hhiiss--
              ttoorryy or nneexxtt--hhiissttoorryy.
       hhiissttoorryy--ssiizzee ((uunnsseett))
              Set the maximum number of history entries saved in  the  history
              list.   If set to zero, any existing history entries are deleted
              and no new entries are saved.  If set to a value less than zero,
              the number of history entries is not limited.  By default,  bbaasshh
              sets  the  maximum number of history entries to the value of the
              HHIISSTTSSIIZZEE shell variable.  Setting _h_i_s_t_o_r_y_-_s_i_z_e to a  non-numeric
              value will set the maximum number of history entries to 500.
       hhoorriizzoonnttaall--ssccrroollll--mmooddee ((OOffff))
              Setting this variable to OOnn makes rreeaaddlliinnee use a single line for
              display,  scrolling  the  input  horizontally on a single screen
              line when it becomes longer than the screen  width  rather  than
              wrapping  to  a new line.  This setting is automatically enabled
              for terminals of height 1.
       iinnppuutt--mmeettaa ((OOffff))
              If set to OOnn, rreeaaddlliinnee enables eight-bit input (that is, it does
              not clear the eighth bit in the characters it reads), regardless
              of what the terminal claims it can support.  The default is _O_f_f,
              but rreeaaddlliinnee sets it to _O_n if  the  locale  contains  characters
              whose encodings may include bytes with the eighth bit set.  This
              variable  is  dependent on the LLCC__CCTTYYPPEE locale category, and its
              value may change if the locale changes.  The name mmeettaa--ffllaagg is a
              synonym for iinnppuutt--mmeettaa.
       iisseeaarrcchh--tteerrmmiinnaattoorrss (("CC--[[CC--jj"))
              The string of characters that should  terminate  an  incremental
              search  without  subsequently  executing the character as a com-
              mand.  If this variable has not been given a value, the  charac-
              ters _E_S_C and CC--jj terminate an incremental search.
       kkeeyymmaapp ((eemmaaccss))
              Set  the current rreeaaddlliinnee keymap.  The set of valid keymap names
              is _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_d_a_r_d_, _e_m_a_c_s_-_m_e_t_a_,  _e_m_a_c_s_-_c_t_l_x_,  _v_i_,  _v_i_-_c_o_m_-
              _m_a_n_d,  and  _v_i_-_i_n_s_e_r_t.  _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d; _e_m_a_c_s is
              equivalent to _e_m_a_c_s_-_s_t_a_n_d_a_r_d.  The default value is  _e_m_a_c_s;  the
              value of eeddiittiinngg--mmooddee also affects the default keymap.
       kkeeyysseeqq--ttiimmeeoouutt ((550000))
              Specifies  the  duration rreeaaddlliinnee will wait for a character when
              reading an ambiguous key sequence (one that can form a  complete
              key sequence using the input read so far, or can take additional
              input  to complete a longer key sequence).  If rreeaaddlliinnee does not
              receive any input within the timeout, it uses  the  shorter  but
              complete  key sequence.  The value is specified in milliseconds,
              so a value of 1000 means that rreeaaddlliinnee will wait one second  for
              additional  input.  If this variable is set to a value less than
              or equal to zero, or to a non-numeric value, rreeaaddlliinnee waits  un-
              til  another key is pressed to decide which key sequence to com-
              plete.
       mmaarrkk--ddiirreeccttoorriieess ((OOnn))
              If set to OOnn, completed directory names have a slash appended.
       mmaarrkk--mmooddiiffiieedd--lliinneess ((OOffff))
              If set to OOnn, rreeaaddlliinnee displays history  lines  that  have  been
              modified with a preceding asterisk (**).
       mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess ((OOffff))
              If set to OOnn, completed names which are symbolic links to direc-
              tories  have  a slash appended, subject to the value of mmaarrkk--ddii--
              rreeccttoorriieess.
       mmaattcchh--hhiiddddeenn--ffiilleess ((OOnn))
              This variable, when set to OOnn, forces rreeaaddlliinnee  to  match  files
              whose  names  begin  with  a "."  (hidden files) when performing
              filename completion.  If set to OOffff, the user must  include  the
              leading "."  in the filename to be completed.
       mmeennuu--ccoommpplleettee--ddiissppllaayy--pprreeffiixx ((OOffff))
              If  set to OOnn, menu completion displays the common prefix of the
              list of possible completions (which may be empty) before cycling
              through the list.
       oouuttppuutt--mmeettaa ((OOffff))
              If set to OOnn, rreeaaddlliinnee displays characters with the  eighth  bit
              set  directly  rather  than  as a meta-prefixed escape sequence.
              The default is _O_f_f, but rreeaaddlliinnee sets it to  _O_n  if  the  locale
              contains  characters  whose encodings may include bytes with the
              eighth bit set.  This variable is dependent on the LLCC__CCTTYYPPEE  lo-
              cale category, and its value may change if the locale changes.
       ppaaggee--ccoommpplleettiioonnss ((OOnn))
              If set to OOnn, rreeaaddlliinnee uses an internal pager resembling _m_o_r_e(1)
              to display a screenful of possible completions at a time.
       pprreeffeerr--vviissiibbllee--bbeellll
              See bbeellll--ssttyyllee.
       pprriinntt--ccoommpplleettiioonnss--hhoorriizzoonnttaallllyy ((OOffff))
              If  set to OOnn, rreeaaddlliinnee displays completions with matches sorted
              horizontally in alphabetical order, rather than down the screen.
       rreevveerrtt--aallll--aatt--nneewwlliinnee ((OOffff))
              If set to OOnn, rreeaaddlliinnee will undo all changes  to  history  lines
              before  returning  when executing aacccceepptt--lliinnee.  By default, his-
              tory lines may be modified  and  retain  individual  undo  lists
              across calls to rreeaaddlliinnee.
       sseeaarrcchh--iiggnnoorree--ccaassee ((OOffff))
              If  set to OOnn, rreeaaddlliinnee performs incremental and non-incremental
              history list searches in a case-insensitive fashion.
       sshhooww--aallll--iiff--aammbbiigguuoouuss ((OOffff))
              This alters the default behavior of  the  completion  functions.
              If set to OOnn, words which have more than one possible completion
              cause  the  matches  to be listed immediately instead of ringing
              the bell.
       sshhooww--aallll--iiff--uunnmmooddiiffiieedd ((OOffff))
              This alters the default behavior of the completion functions  in
              a fashion similar to sshhooww--aallll--iiff--aammbbiigguuoouuss.  If set to OOnn, words
              which  have more than one possible completion without any possi-
              ble partial completion (the possible completions don't  share  a
              common  prefix)  cause  the matches to be listed immediately in-
              stead of ringing the bell.
       sshhooww--mmooddee--iinn--pprroommpptt ((OOffff))
              If set to OOnn, add a string to the beginning of the prompt  indi-
              cating  the  editing  mode:  emacs, vi command, or vi insertion.
              The mode strings are user-settable (e.g., _e_m_a_c_s_-_m_o_d_e_-_s_t_r_i_n_g).
       sskkiipp--ccoommpplleetteedd--tteexxtt ((OOffff))
              If set to OOnn, this alters the default completion  behavior  when
              inserting  a  single match into the line.  It's only active when
              performing completion in the middle  of  a  word.   If  enabled,
              rreeaaddlliinnee  does  not  insert  characters from the completion that
              match characters after point in the  word  being  completed,  so
              portions of the word following the cursor are not duplicated.
       vvii--ccmmdd--mmooddee--ssttrriinngg ((((ccmmdd))))
              If  the  _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this string is
              displayed immediately before the last line of the primary prompt
              when vi editing mode is active and in command mode.   The  value
              is expanded like a key binding, so the standard set of meta- and
              control-  prefixes  and backslash escape sequences is available.
              The \1 and \2 escapes begin and end  sequences  of  non-printing
              characters,  which  can  be used to embed a terminal control se-
              quence into the mode string.
       vvii--iinnss--mmooddee--ssttrriinngg ((((iinnss))))
              If the _s_h_o_w_-_m_o_d_e_-_i_n_-_p_r_o_m_p_t variable is enabled, this  string  is
              displayed immediately before the last line of the primary prompt
              when vi editing mode is active and in insertion mode.  The value
              is expanded like a key binding, so the standard set of meta- and
              control-  prefixes  and backslash escape sequences is available.
              The \1 and \2 escapes begin and end  sequences  of  non-printing
              characters,  which  can  be used to embed a terminal control se-
              quence into the mode string.
       vviissiibbllee--ssttaattss ((OOffff))
              If set to OOnn, a character denoting a file's type as reported  by
              _s_t_a_t(2)  is  appended to the filename when listing possible com-
              pletions.

   RReeaaddlliinnee CCoonnddiittiioonnaall CCoonnssttrruuccttss
       RReeaaddlliinnee implements a facility similar in  spirit  to  the  conditional
       compilation  features  of  the C preprocessor which allows key bindings
       and variable settings to be performed as the result  of  tests.   There
       are four parser directives available.

       $$iiff    The  $$iiff construct allows bindings to be made based on the edit-
              ing mode, the terminal being  used,  or  the  application  using
              rreeaaddlliinnee.   The text of the test, after any comparison operator,
              extends to the end of the line; unless otherwise noted, no char-
              acters are required to isolate it.

              mmooddee   The mmooddee== form of the  $$iiff  directive  is  used  to  test
                     whether  rreeaaddlliinnee  is  in  emacs or vi mode.  This may be
                     used in conjunction with the sseett kkeeyymmaapp command, for  in-
                     stance,   to  set  bindings  in  the  _e_m_a_c_s_-_s_t_a_n_d_a_r_d  and
                     _e_m_a_c_s_-_c_t_l_x keymaps only if rreeaaddlliinnee is  starting  out  in
                     emacs mode.

              tteerrmm   The  tteerrmm==  form may be used to include terminal-specific
                     key bindings, perhaps to bind the key sequences output by
                     the terminal's function keys.  The word on the right side
                     of the == is tested against both the full name of the ter-
                     minal and the portion of the  terminal  name  before  the
                     first  --.   This  allows  _x_t_e_r_m  to  match both _x_t_e_r_m and
                     _x_t_e_r_m_-_2_5_6_c_o_l_o_r, for instance.

              vveerrssiioonn
                     The vveerrssiioonn test  may  be  used  to  perform  comparisons
                     against  specific rreeaaddlliinnee versions.  The vveerrssiioonn expands
                     to the current rreeaaddlliinnee version.  The set  of  comparison
                     operators  includes  ==,  (and  ====), !!==, <<==, >>==, <<, and >>.
                     The version number supplied on the right side of the  op-
                     erator  consists  of  a major version number, an optional
                     decimal point, and an optional minor version (e.g., 77..11).
                     If the minor version is omitted, it defaults to  00.   The
                     operator  may  be  separated  from the string vveerrssiioonn and
                     from the version number argument by whitespace.

              _a_p_p_l_i_c_a_t_i_o_n
                     The _a_p_p_l_i_c_a_t_i_o_n construct is used to include application-
                     specific settings.  Each program using the  rreeaaddlliinnee  li-
                     brary  sets  the  _a_p_p_l_i_c_a_t_i_o_n _n_a_m_e, and an initialization
                     file can test for a particular value.  This could be used
                     to bind key sequences to functions useful for a  specific
                     program.   For instance, the following command adds a key
                     sequence that quotes the  current  or  previous  word  in
                     bbaasshh:

                     $$iiff Bash
                     # Quote the current or previous word
                     "\C-xq": "\eb\"\ef\""
                     $$eennddiiff

              _v_a_r_i_a_b_l_e
                     The _v_a_r_i_a_b_l_e construct provides simple equality tests for
                     rreeaaddlliinnee  variables and values.  The permitted comparison
                     operators are _=, _=_=, and _!_=.  The variable name  must  be
                     separated from the comparison operator by whitespace; the
                     operator  may  be  separated  from the value on the right
                     hand side by whitespace.  String  and  boolean  variables
                     may  be tested.  Boolean variables must be tested against
                     the values _o_n and _o_f_f.

       $$eellssee  Commands in this branch of the $$iiff directive are executed if the
              test fails.

       $$eennddiiff This command, as seen in the previous example, terminates an $$iiff
              command.

       $$iinncclluuddee
              This directive takes a single filename as an argument and  reads
              commands and key bindings from that file.  For example, the fol-
              lowing directive would read _/_e_t_c_/_i_n_p_u_t_r_c:

              $$iinncclluuddee  _/_e_t_c_/_i_n_p_u_t_r_c

   SSeeaarrcchhiinngg
       RReeaaddlliinnee  provides  commands  for searching through the command history
       (see HHIISSTTOORRYY below) for lines containing a specified string.  There are
       two search modes: _i_n_c_r_e_m_e_n_t_a_l and _n_o_n_-_i_n_c_r_e_m_e_n_t_a_l.

       Incremental searches begin before the  user  has  finished  typing  the
       search  string.  As each character of the search string is typed, rreeaadd--
       lliinnee displays the next entry from the history matching the string typed
       so far.  An incremental search requires  only  as  many  characters  as
       needed  to  find  the  desired history entry.  When using emacs editing
       mode, type CC--rr to search backward  in  the  history  for  a  particular
       string.   Typing CC--ss searches forward through the history.  The charac-
       ters present in the value of the iisseeaarrcchh--tteerrmmiinnaattoorrss variable are  used
       to  terminate an incremental search.  If that variable has not been as-
       signed a value, _E_S_C and  CC--jj  terminate  an  incremental  search.   CC--gg
       aborts  an incremental search and restores the original line.  When the
       search is terminated, the history entry containing  the  search  string
       becomes the current line.

       To  find other matching entries in the history list, type CC--rr or CC--ss as
       appropriate.  This searches backward or forward in the history for  the
       next  entry matching the search string typed so far.  Any other key se-
       quence bound to a rreeaaddlliinnee command terminates the search  and  executes
       that  command.   For  instance, a newline terminates the search and ac-
       cepts the line, thereby executing the command from the history list.  A
       movement command will terminate the search, make the  last  line  found
       the current line, and begin editing.

       RReeaaddlliinnee remembers the last incremental search string.  If two CC--rrs are
       typed  without any intervening characters defining a new search string,
       rreeaaddlliinnee uses any remembered search string.

       Non-incremental searches read the entire search string before  starting
       to search for matching history entries.  The search string may be typed
       by the user or be part of the contents of the current line.

   RReeaaddlliinnee CCoommmmaanndd NNaammeess
       The  following  is  a list of the names of the commands and the default
       key sequences to which they are bound.  Command names without an accom-
       panying key sequence are unbound by default.

       In the following descriptions, _p_o_i_n_t refers to the current cursor posi-
       tion, and _m_a_r_k refers to a cursor position saved by the  sseett--mmaarrkk  com-
       mand.   The  text  between the point and mark is referred to as the _r_e_-
       _g_i_o_n.  RReeaaddlliinnee has the concept of an _a_c_t_i_v_e _r_e_g_i_o_n: when the region is
       active, rreeaaddlliinnee redisplay highlights the region using the value of the
       aaccttiivvee--rreeggiioonn--ssttaarrtt--ccoolloorr variable.  The eennaabbllee--aaccttiivvee--rreeggiioonn  rreeaaddlliinnee
       variable turns this on and off.  Several commands set the region to ac-
       tive; those are noted below.

   CCoommmmaannddss ffoorr MMoovviinngg
       bbeeggiinnnniinngg--ooff--lliinnee ((CC--aa))
              Move  to  the start of the current line.  This may also be bound
              to the Home key on some keyboards.
       eenndd--ooff--lliinnee ((CC--ee))
              Move to the end of the line.  This may also be bound to the  End
              key on some keyboards.
       ffoorrwwaarrdd--cchhaarr ((CC--ff))
              Move  forward  a character.  This may also be bound to the right
              arrow key on some keyboards.
       bbaacckkwwaarrdd--cchhaarr ((CC--bb))
              Move back a character.  This may also be bound to the left arrow
              key on some keyboards.
       ffoorrwwaarrdd--wwoorrdd ((MM--ff))
              Move forward to the end of the next word.  Words are composed of
              alphanumeric characters (letters and digits).
       bbaacckkwwaarrdd--wwoorrdd ((MM--bb))
              Move back to the start of the current or previous  word.   Words
              are composed of alphanumeric characters (letters and digits).
       sshheellll--ffoorrwwaarrdd--wwoorrdd ((MM--CC--ff))
              Move  forward  to the end of the next word.  Words are delimited
              by non-quoted shell metacharacters.
       sshheellll--bbaacckkwwaarrdd--wwoorrdd ((MM--CC--bb))
              Move back to the start of the current or previous  word.   Words
              are delimited by non-quoted shell metacharacters.
       pprreevviioouuss--ssccrreeeenn--lliinnee
              Attempt  to move point to the same physical screen column on the
              previous physical screen line.  This will not have  the  desired
              effect  if  the current rreeaaddlliinnee line does not take up more than
              one physical line or if point is not greater than the length  of
              the prompt plus the screen width.
       nneexxtt--ssccrreeeenn--lliinnee
              Attempt  to move point to the same physical screen column on the
              next physical screen line.  This will not have the  desired  ef-
              fect if the current rreeaaddlliinnee line does not take up more than one
              physical  line  or if the length of the current rreeaaddlliinnee line is
              not greater than the length of the prompt plus the screen width.
       cclleeaarr--ddiissppllaayy ((MM--CC--ll))
              Clear the screen and, if  possible,  the  terminal's  scrollback
              buffer,  then  redraw the current line, leaving the current line
              at the top of the screen.
       cclleeaarr--ssccrreeeenn ((CC--ll))
              Clear the screen, then redraw the current line, leaving the cur-
              rent line at the top of the screen.  With  a  numeric  argument,
              refresh the current line without clearing the screen.
       rreeddrraaww--ccuurrrreenntt--lliinnee
              Refresh the current line.

   CCoommmmaannddss ffoorr MMaanniippuullaattiinngg tthhee HHiissttoorryy
       aacccceepptt--lliinnee ((NNeewwlliinnee,, RReettuurrnn))
              Accept the line regardless of where the cursor is.  If this line
              is  non-empty, add it to the history list according to the state
              of the HHIISSTTCCOONNTTRROOLL and HHIISSTTIIGGNNOORREE variables.  If the line  is  a
              modified  history line, restore the history line to its original
              state.
       pprreevviioouuss--hhiissttoorryy ((CC--pp))
              Fetch the previous command from the history list, moving back in
              the list.  This may also be bound to the up arrow  key  on  some
              keyboards.
       nneexxtt--hhiissttoorryy ((CC--nn))
              Fetch  the next command from the history list, moving forward in
              the list.  This may also be bound to the down arrow key on  some
              keyboards.
       bbeeggiinnnniinngg--ooff--hhiissttoorryy ((MM--<<))
              Move to the first line in the history.
       eenndd--ooff--hhiissttoorryy ((MM-->>))
              Move  to  the end of the input history, i.e., the line currently
              being entered.
       ooppeerraattee--aanndd--ggeett--nneexxtt ((CC--oo))
              Accept the current line for execution as if a newline  had  been
              entered,  and  fetch  the next line relative to the current line
              from the history for editing.  A numeric argument, if  supplied,
              specifies the history entry to use instead of the current line.
       ffeettcchh--hhiissttoorryy
              With  a numeric argument, fetch that entry from the history list
              and make it the current line.  Without an argument, move back to
              the first entry in the history list.
       rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((CC--rr))
              Search backward starting at the current  line  and  moving  "up"
              through  the  history  as  necessary.   This  is  an incremental
              search.  This command sets the region to the  matched  text  and
              activates the region.
       ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((CC--ss))
              Search  forward  starting  at the current line and moving "down"
              through the  history  as  necessary.   This  is  an  incremental
              search.   This  command  sets the region to the matched text and
              activates the region.
       nnoonn--iinnccrreemmeennttaall--rreevveerrssee--sseeaarrcchh--hhiissttoorryy ((MM--pp))
              Search backward through the history starting at the current line
              using a non-incremental search for  a  string  supplied  by  the
              user.  The search string may match anywhere in a history line.
       nnoonn--iinnccrreemmeennttaall--ffoorrwwaarrdd--sseeaarrcchh--hhiissttoorryy ((MM--nn))
              Search  forward  through  the  history  using  a non-incremental
              search for a string supplied by the user.  The search string may
              match anywhere in a history line.
       hhiissttoorryy--sseeaarrcchh--bbaacckkwwaarrdd
              Search backward through the history for the string of characters
              between the start of the current line and the point.  The search
              string must match at the beginning of a history line.  This is a
              non-incremental search.  This may be bound to the Page Up key on
              some keyboards.
       hhiissttoorryy--sseeaarrcchh--ffoorrwwaarrdd
              Search forward through the history for the string of  characters
              between the start of the current line and the point.  The search
              string must match at the beginning of a history line.  This is a
              non-incremental  search.  This may be bound to the Page Down key
              on some keyboards.
       hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--bbaacckkwwaarrdd
              Search backward through the history for the string of characters
              between the start of the current line and the point.  The search
              string may match anywhere in a history line.  This is a  non-in-
              cremental search.
       hhiissttoorryy--ssuubbssttrriinngg--sseeaarrcchh--ffoorrwwaarrdd
              Search  forward through the history for the string of characters
              between the start of the current line and the point.  The search
              string may match anywhere in a history line.  This is a  non-in-
              cremental search.
       yyaannkk--nntthh--aarrgg ((MM--CC--yy))
              Insert  the  first argument to the previous command (usually the
              second word on the previous line) at point.  With an argument _n,
              insert the _nth word from the previous command (the words in  the
              previous  command  begin  with word 0).  A negative argument in-
              serts the _nth word from the end of the previous  command.   Once
              the  argument _n is computed, this uses the history expansion fa-
              cilities to extract the _nth word, as if the "!_n" history  expan-
              sion had been specified.
       yyaannkk--llaasstt--aarrgg ((MM--..,, MM--__))
              Insert  the last argument to the previous command (the last word
              of the previous history entry).  With a numeric argument, behave
              exactly like yyaannkk--nntthh--aarrgg.  Successive  calls  to  yyaannkk--llaasstt--aarrgg
              move  back through the history list, inserting the last word (or
              the word specified by the argument to the first  call)  of  each
              line in turn.  Any numeric argument supplied to these successive
              calls  determines  the direction to move through the history.  A
              negative argument switches the  direction  through  the  history
              (back  or  forward).  This uses the history expansion facilities
              to extract the last word, as if the "!$" history  expansion  had
              been specified.
       sshheellll--eexxppaanndd--lliinnee ((MM--CC--ee))
              Expand  the line by performing shell word expansions.  This per-
              forms alias and history expansion, $$'_s_t_r_i_n_g' and $$"_s_t_r_i_n_g" quot-
              ing, tilde expansion, parameter and variable  expansion,  arith-
              metic  expansion,  command and process substitution, word split-
              ting, and quote removal.  An explicit argument  suppresses  com-
              mand  and process substitution.  See HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for
              a description of history expansion.
       hhiissttoorryy--eexxppaanndd--lliinnee ((MM--^^))
              Perform history expansion on the current line.  See HHIISSTTOORRYY  EEXX--
              PPAANNSSIIOONN below for a description of history expansion.
       mmaaggiicc--ssppaaccee
              Perform  history  expansion  on  the  current  line and insert a
              space.  See HHIISSTTOORRYY EEXXPPAANNSSIIOONN below for a description of history
              expansion.
       aalliiaass--eexxppaanndd--lliinnee
              Perform alias expansion on the current line.  See AALLIIAASSEESS  above
              for a description of alias expansion.
       hhiissttoorryy--aanndd--aalliiaass--eexxppaanndd--lliinnee
              Perform history and alias expansion on the current line.
       iinnsseerrtt--llaasstt--aarrgguummeenntt ((MM--..,, MM--__))
              A synonym for yyaannkk--llaasstt--aarrgg.
       eeddiitt--aanndd--eexxeeccuuttee--ccoommmmaanndd ((CC--xx CC--ee))
              Invoke  an  editor  on the current command line, and execute the
              result as shell commands.  BBaasshh attempts to invoke $$VVIISSUUAALL, $$EEDD--
              IITTOORR, and _e_m_a_c_s as the editor, in that order.

   CCoommmmaannddss ffoorr CChhaannggiinngg TTeexxtt
       _e_n_d_-_o_f_-_f_i_l_e ((uussuuaallllyy CC--dd))
              The character indicating end-of-file as  set,  for  example,  by
              _s_t_t_y(1).  If this character is read when there are no characters
              on the line, and point is at the beginning of the line, rreeaaddlliinnee
              interprets it as the end of input and returns EEOOFF.
       ddeelleettee--cchhaarr ((CC--dd))
              Delete the character at point.  If this function is bound to the
              same character as the tty EEOOFF character, as CC--dd commonly is, see
              above for the effects.  This may also be bound to the Delete key
              on some keyboards.
       bbaacckkwwaarrdd--ddeelleettee--cchhaarr ((RRuubboouutt))
              Delete  the  character  behind the cursor.  When given a numeric
              argument, save the deleted text on the kill ring.
       ffoorrwwaarrdd--bbaacckkwwaarrdd--ddeelleettee--cchhaarr
              Delete the character under the cursor, unless the cursor  is  at
              the end of the line, in which case the character behind the cur-
              sor is deleted.
       qquuootteedd--iinnsseerrtt ((CC--qq,, CC--vv))
              Add  the next character typed to the line verbatim.  This is how
              to insert characters like CC--qq, for example.
       ttaabb--iinnsseerrtt ((CC--vv TTAABB))
              Insert a tab character.
       sseellff--iinnsseerrtt ((aa,, bb,, AA,, 11,, !!,, ...))
              Insert the character typed.
       bbrraacckkeetteedd--ppaassttee--bbeeggiinn
              This function is intended to be bound to the  "bracketed  paste"
              escape  sequence  sent  by some terminals, and such a binding is
              assigned by default.  It allows rreeaaddlliinnee to  insert  the  pasted
              text  as  a single unit without treating each character as if it
              had been read from the keyboard.  The pasted characters are  in-
              serted  as  if each one was bound to sseellff--iinnsseerrtt instead of exe-
              cuting any editing commands.
              Bracketed paste sets the region to the inserted text  and  acti-
              vates the region.
       ttrraannssppoossee--cchhaarrss ((CC--tt))
              Drag  the  character  before point forward over the character at
              point, moving point forward as well.  If point is at the end  of
              the  line, then this transposes the two characters before point.
              Negative arguments have no effect.
       ttrraannssppoossee--wwoorrddss ((MM--tt))
              Drag the word before point past the  word  after  point,  moving
              point  past  that  word  as well.  If point is at the end of the
              line, this transposes the last two words on the line.
       sshheellll--ttrraannssppoossee--wwoorrddss ((MM--CC--tt))
              Drag the word before point past the  word  after  point,  moving
              point  past that word as well.  If the insertion point is at the
              end of the line, this transposes the last two words on the line.
              Word  boundaries  are  the  same   as   sshheellll--ffoorrwwaarrdd--wwoorrdd   and
              sshheellll--bbaacckkwwaarrdd--wwoorrdd.
       uuppccaassee--wwoorrdd ((MM--uu))
              Uppercase  the current (or following) word.  With a negative ar-
              gument, uppercase the previous word, but do not move point.
       ddoowwnnccaassee--wwoorrdd ((MM--ll))
              Lowercase the current (or following) word.  With a negative  ar-
              gument, lowercase the previous word, but do not move point.
       ccaappiittaalliizzee--wwoorrdd ((MM--cc))
              Capitalize the current (or following) word.  With a negative ar-
              gument, capitalize the previous word, but do not move point.
       oovveerrwwrriittee--mmooddee
              Toggle  overwrite mode.  With an explicit positive numeric argu-
              ment, switches to overwrite mode.  With an explicit non-positive
              numeric argument, switches to insert mode.  This command affects
              only eemmaaccss mode; vvii mode does overwrite differently.  Each  call
              to _r_e_a_d_l_i_n_e_(_) starts in insert mode.
              In  overwrite  mode, characters bound to sseellff--iinnsseerrtt replace the
              text at point rather than pushing the text to the right.   Char-
              acters  bound  to bbaacckkwwaarrdd--ddeelleettee--cchhaarr replace the character be-
              fore point with a space.  By default, this command  is  unbound,
              but may be bound to the Insert key on some keyboards.

   KKiilllliinngg aanndd YYaannkkiinngg
       kkiillll--lliinnee ((CC--kk))
              Kill the text from point to the end of the current line.  With a
              negative  numeric argument, kill backward from the cursor to the
              beginning of the line.
       bbaacckkwwaarrdd--kkiillll--lliinnee ((CC--xx RRuubboouutt))
              Kill backward to the beginning of the current line.  With a neg-
              ative numeric argument, kill forward from the cursor to the  end
              of the line.
       uunniixx--lliinnee--ddiissccaarrdd ((CC--uu))
              Kill  backward  from  point to the beginning of the line, saving
              the killed text on the kill-ring.
       kkiillll--wwhhoollee--lliinnee
              Kill all characters on the current line, no matter  where  point
              is.
       kkiillll--wwoorrdd ((MM--dd))
              Kill  from  point  to the end of the current word, or if between
              words, to the end of the next word.   Word  boundaries  are  the
              same as those used by ffoorrwwaarrdd--wwoorrdd.
       bbaacckkwwaarrdd--kkiillll--wwoorrdd ((MM--RRuubboouutt))
              Kill  the  word  behind  point.  Word boundaries are the same as
              those used by bbaacckkwwaarrdd--wwoorrdd.
       sshheellll--kkiillll--wwoorrdd ((MM--CC--dd))
              Kill from point to the end of the current word,  or  if  between
              words,  to  the  end  of the next word.  Word boundaries are the
              same as those used by sshheellll--ffoorrwwaarrdd--wwoorrdd.
       sshheellll--bbaacckkwwaarrdd--kkiillll--wwoorrdd
              Kill the word behind point.  Word boundaries  are  the  same  as
              those used by sshheellll--bbaacckkwwaarrdd--wwoorrdd.
       uunniixx--wwoorrdd--rruubboouutt ((CC--ww))
              Kill  the  word behind point, using white space as a word bound-
              ary, saving the killed text on the kill-ring.
       uunniixx--ffiilleennaammee--rruubboouutt
              Kill the word behind point, using  white  space  and  the  slash
              character  as the word boundaries, saving the killed text on the
              kill-ring.
       ddeelleettee--hhoorriizzoonnttaall--ssppaaccee ((MM--\\))
              Delete all spaces and tabs around point.
       kkiillll--rreeggiioonn
              Kill the text in the current region.
       ccooppyy--rreeggiioonn--aass--kkiillll
              Copy the text in the region to the kill buffer,  so  it  can  be
              yanked immediately.
       ccooppyy--bbaacckkwwaarrdd--wwoorrdd
              Copy  the word before point to the kill buffer.  The word bound-
              aries are the same as bbaacckkwwaarrdd--wwoorrdd.
       ccooppyy--ffoorrwwaarrdd--wwoorrdd
              Copy the word following point to  the  kill  buffer.   The  word
              boundaries are the same as ffoorrwwaarrdd--wwoorrdd.
       yyaannkk ((CC--yy))
              Yank the top of the kill ring into the buffer at point.
       yyaannkk--ppoopp ((MM--yy))
              Rotate  the kill ring, and yank the new top.  Only works follow-
              ing yyaannkk or yyaannkk--ppoopp.

   NNuummeerriicc AArrgguummeennttss
       ddiiggiitt--aarrgguummeenntt ((MM--00,, MM--11,, ...,, MM----))
              Add this digit to the argument already accumulating, or start  a
              new argument.  M-- starts a negative argument.
       uunniivveerrssaall--aarrgguummeenntt
              This  is another way to specify an argument.  If this command is
              followed by one or more digits, optionally with a leading  minus
              sign,  those digits define the argument.  If the command is fol-
              lowed by digits, executing uunniivveerrssaall--aarrgguummeenntt again ends the nu-
              meric argument, but is otherwise ignored.  As a special case, if
              this command is immediately followed by a character that is nei-
              ther a digit nor minus sign, the argument  count  for  the  next
              command  is multiplied by four.  The argument count is initially
              one, so executing this function the first time makes  the  argu-
              ment count four, a second time makes the argument count sixteen,
              and so on.

   CCoommpplleettiinngg
       ccoommpplleettee ((TTAABB))
              Attempt  to  perform  completion on the text before point.  BBaasshh
              attempts completion by first checking for any programmable  com-
              pletions  for  the command word (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn be-
              low), otherwise treating the text as a variable (if the text be-
              gins with $$), username (if the text begins with ~~), hostname (if
              the text begins with @@), or command  (including  aliases,  func-
              tions,  and  builtins)  in  turn.   If  none of these produces a
              match, it falls back to filename completion.
       ppoossssiibbllee--ccoommpplleettiioonnss ((MM--??))
              List the possible completions of the text  before  point.   When
              displaying completions, rreeaaddlliinnee sets the number of columns used
              for  display to the value of ccoommpplleettiioonn--ddiissppllaayy--wwiiddtthh, the value
              of the shell variable CCOOLLUUMMNNSS, or the screen width, in that  or-
              der.
       iinnsseerrtt--ccoommpplleettiioonnss ((MM--**))
              Insert  all completions of the text before point that would have
              been generated by ppoossssiibbllee--ccoommpplleettiioonnss, separated by a space.
       mmeennuu--ccoommpplleettee
              Similar to ccoommpplleettee, but replaces the word to be completed  with
              a  single  match from the list of possible completions.  Repeat-
              edly executing mmeennuu--ccoommpplleettee steps through the list of  possible
              completions,  inserting  each  match in turn.  At the end of the
              list of completions, mmeennuu--ccoommpplleettee rings the  bell  (subject  to
              the  setting  of bbeellll--ssttyyllee) and restores the original text.  An
              argument of _n moves _n positions forward in the list of  matches;
              a  negative argument moves backward through the list.  This com-
              mand is intended to be bound to TTAABB, but is unbound by default.
       mmeennuu--ccoommpplleettee--bbaacckkwwaarrdd
              Identical to mmeennuu--ccoommpplleettee, but moves backward through the  list
              of  possible  completions,  as if mmeennuu--ccoommpplleettee had been given a
              negative argument.  This command is unbound by default.
       eexxppoorrtt--ccoommpplleettiioonnss
              Perform completion on the word before point as  described  above
              and  write the list of possible completions to rreeaaddlliinnee's output
              stream using the following format, writing information on  sepa-
              rate lines:

              +o      the number of matches _N;
              +o      the word being completed;
              +o      _S:_E,  where  _S and _E are the start and end offsets of the
                     word in the rreeaaddlliinnee line buffer; then
              +o      each match, one per line

              If there are no matches, the first line will be  "0",  and  this
              command  does  not  print any output after the _S:_E.  If there is
              only a single match, this prints a single  line  containing  it.
              If  there  is more than one match, this prints the common prefix
              of the matches, which may be empty, on the first line after  the
              _S:_E, then the matches on subsequent lines.  In this case, _N will
              include the first line with the common prefix.

              The user or application should be able to accommodate the possi-
              bility of a blank line.  The intent is that the user or applica-
              tion  reads  _N lines after the line containing _S:_E to obtain the
              match list.  This command is unbound by default.

       ddeelleettee--cchhaarr--oorr--lliisstt
              Deletes the character under the cursor if not at  the  beginning
              or  end of the line (like ddeelleettee--cchhaarr).  At the end of the line,
              it behaves identically to ppoossssiibbllee--ccoommpplleettiioonnss.  This command is
              unbound by default.

       ccoommpplleettee--ffiilleennaammee ((MM--//))
              Attempt filename completion on the text before point.

       ppoossssiibbllee--ffiilleennaammee--ccoommpplleettiioonnss ((CC--xx //))
              List the possible completions of the text before point, treating
              it as a filename.

       ccoommpplleettee--uusseerrnnaammee ((MM--~~))
              Attempt completion on the text before point, treating  it  as  a
              username.

       ppoossssiibbllee--uusseerrnnaammee--ccoommpplleettiioonnss ((CC--xx ~~))
              List the possible completions of the text before point, treating
              it as a username.

       ccoommpplleettee--vvaarriiaabbllee ((MM--$$))
              Attempt  completion  on  the text before point, treating it as a
              shell variable.

       ppoossssiibbllee--vvaarriiaabbllee--ccoommpplleettiioonnss ((CC--xx $$))
              List the possible completions of the text before point, treating
              it as a shell variable.

       ccoommpplleettee--hhoossttnnaammee ((MM--@@))
              Attempt completion on the text before point, treating  it  as  a
              hostname.

       ppoossssiibbllee--hhoossttnnaammee--ccoommpplleettiioonnss ((CC--xx @@))
              List the possible completions of the text before point, treating
              it as a hostname.

       ccoommpplleettee--ccoommmmaanndd ((MM--!!))
              Attempt  completion  on  the text before point, treating it as a
              command name.  Command completion attempts  to  match  the  text
              against   aliases,   reserved   words,  shell  functions,  shell
              builtins, and finally executable filenames, in that order.

       ppoossssiibbllee--ccoommmmaanndd--ccoommpplleettiioonnss ((CC--xx !!))
              List the possible completions of the text before point, treating
              it as a command name.

       ddyynnaammiicc--ccoommpplleettee--hhiissttoorryy ((MM--TTAABB))
              Attempt completion on the text before point, comparing the  text
              against history list entries for possible completion matches.

       ddaabbbbrreevv--eexxppaanndd
              Attempt  menu completion on the text before point, comparing the
              text against lines from the history list for possible completion
              matches.

       ccoommpplleettee--iinnttoo--bbrraacceess ((MM--{{))
              Perform filename completion and insert the list of possible com-
              pletions enclosed within braces so the list is available to  the
              shell (see BBrraaccee EExxppaannssiioonn above).

   KKeeyybbooaarrdd MMaaccrrooss
       ssttaarrtt--kkbbdd--mmaaccrroo ((CC--xx (())
              Begin  saving  the  characters  typed  into the current keyboard
              macro.
       eenndd--kkbbdd--mmaaccrroo ((CC--xx ))))
              Stop saving the characters typed into the current keyboard macro
              and store the definition.
       ccaallll--llaasstt--kkbbdd--mmaaccrroo ((CC--xx ee))
              Re-execute the last keyboard macro defined, by making the  char-
              acters in the macro appear as if typed at the keyboard.
       pprriinntt--llaasstt--kkbbdd--mmaaccrroo (())
              Print  the  last keyboard macro defined in a format suitable for
              the _i_n_p_u_t_r_c file.

   MMiisscceellllaanneeoouuss
       rree--rreeaadd--iinniitt--ffiillee ((CC--xx CC--rr))
              Read in the contents of the _i_n_p_u_t_r_c file,  and  incorporate  any
              bindings or variable assignments found there.
       aabboorrtt ((CC--gg))
              Abort  the  current editing command and ring the terminal's bell
              (subject to the setting of bbeellll--ssttyyllee).
       ddoo--lloowweerrccaassee--vveerrssiioonn ((MM--AA,, MM--BB,, MM--_x,, ...))
              If the metafied character _x is uppercase, run the  command  that
              is bound to the corresponding metafied lowercase character.  The
              behavior is undefined if _x is already lowercase.
       pprreeffiixx--mmeettaa ((EESSCC))
              Metafy the next character typed.  EESSCC ff is equivalent to MMeettaa--ff.
       uunnddoo ((CC--__,, CC--xx CC--uu))
              Incremental undo, separately remembered for each line.
       rreevveerrtt--lliinnee ((MM--rr))
              Undo  all changes made to this line.  This is like executing the
              uunnddoo command enough times to return  the  line  to  its  initial
              state.
       ttiillddee--eexxppaanndd ((MM--&&))
              Perform tilde expansion on the current word.
       sseett--mmaarrkk ((CC--@@,, MM--<<ssppaaccee>>))
              Set  the  mark to the point.  If a numeric argument is supplied,
              set the mark to that position.
       eexxcchhaannggee--ppooiinntt--aanndd--mmaarrkk ((CC--xx CC--xx))
              Swap the point with the mark.  Set the current  cursor  position
              to the saved position, then set the mark to the old cursor posi-
              tion.
       cchhaarraacctteerr--sseeaarrcchh ((CC--]]))
              Read  a  character and move point to the next occurrence of that
              character.  A negative argument  searches  for  previous  occur-
              rences.
       cchhaarraacctteerr--sseeaarrcchh--bbaacckkwwaarrdd ((MM--CC--]]))
              Read  a  character  and move point to the previous occurrence of
              that character.  A negative argument searches for subsequent oc-
              currences.
       sskkiipp--ccssii--sseeqquueennccee
              Read enough characters to consume a multi-key sequence  such  as
              those  defined  for keys like Home and End.  CSI sequences begin
              with a Control Sequence Indicator (CSI), usually _E_S_C _[.  If this
              sequence is bound to "\e[", keys producing CSI sequences have no
              effect unless explicitly bound to a rreeaaddlliinnee command, instead of
              inserting stray characters into the editing buffer.  This is un-
              bound by default, but usually bound to _E_S_C _[.
       iinnsseerrtt--ccoommmmeenntt ((MM--##))
              Without a numeric argument, insert the  value  of  the  rreeaaddlliinnee
              ccoommmmeenntt--bbeeggiinn variable at the beginning of the current line.  If
              a  numeric  argument is supplied, this command acts as a toggle:
              if the characters at the beginning of the line do not match  the
              value  of  ccoommmmeenntt--bbeeggiinn, insert the value; otherwise delete the
              characters in ccoommmmeenntt--bbeeggiinn from the beginning of the line.   In
              either  case,  the  line  is  accepted  as if a newline had been
              typed.  The default value of ccoommmmeenntt--bbeeggiinn causes  this  command
              to make the current line a shell comment.  If a numeric argument
              causes the comment character to be removed, the line will be ex-
              ecuted by the shell.
       ssppeellll--ccoorrrreecctt--wwoorrdd ((CC--xx ss))
              Perform  spelling correction on the current word, treating it as
              a directory or filename, in the same way as  the  ccddssppeellll  shell
              option.    Word  boundaries  are  the  same  as  those  used  by
              sshheellll--ffoorrwwaarrdd--wwoorrdd.
       gglloobb--ccoommpplleettee--wwoorrdd ((MM--gg))
              Treat the word before point as a pattern for pathname expansion,
              with an asterisk implicitly appended, then use  the  pattern  to
              generate a list of matching file names for possible completions.
       gglloobb--eexxppaanndd--wwoorrdd ((CC--xx **))
              Treat the word before point as a pattern for pathname expansion,
              and  insert the list of matching file names, replacing the word.
              If a numeric argument is supplied, append a  **  before  pathname
              expansion.
       gglloobb--lliisstt--eexxppaannssiioonnss ((CC--xx gg))
              Display the list of expansions that would have been generated by
              gglloobb--eexxppaanndd--wwoorrdd  and redisplay the line.  If a numeric argument
              is supplied, append a ** before pathname expansion.
       dduummpp--ffuunnccttiioonnss
              Print all of the functions and their key bindings to  the  rreeaadd--
              lliinnee output stream.  If a numeric argument is supplied, the out-
              put  is  formatted  in such a way that it can be made part of an
              _i_n_p_u_t_r_c file.
       dduummpp--vvaarriiaabblleess
              Print all of the settable rreeaaddlliinnee variables and their values to
              the rreeaaddlliinnee output stream.  If a numeric argument is  supplied,
              the  output  is formatted in such a way that it can be made part
              of an _i_n_p_u_t_r_c file.
       dduummpp--mmaaccrrooss
              Print all of the rreeaaddlliinnee key sequences bound to macros and  the
              strings they output to the rreeaaddlliinnee output stream.  If a numeric
              argument is supplied, the output is formatted in such a way that
              it can be made part of an _i_n_p_u_t_r_c file.
       eexxeeccuuttee--nnaammeedd--ccoommmmaanndd ((MM--xx))
              Read a bindable rreeaaddlliinnee command name from the input and execute
              the  function  to  which  it's  bound, as if the key sequence to
              which it was bound appeared in the input.  If this  function  is
              supplied with a numeric argument, it passes that argument to the
              function it executes.
       ddiissppllaayy--sshheellll--vveerrssiioonn ((CC--xx CC--vv))
              Display version information about the current instance of bbaasshh.

   PPrrooggrraammmmaabbllee CCoommpplleettiioonn
       When  a user attempts word completion for a command or an argument to a
       command for which a completion specification (a _c_o_m_p_s_p_e_c) has been  de-
       fined  using  the  ccoommpplleettee builtin (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below),
       rreeaaddlliinnee invokes the programmable completion facilities.

       First, bbaasshh identifies the command name.  If a compspec  has  been  de-
       fined  for  that  command, the compspec is used to generate the list of
       possible completions for the word.  If the command word  is  the  empty
       string  (completion  attempted at the beginning of an empty line), bbaasshh
       uses any compspec defined with the --EE option to ccoommpplleettee.  The  --II  op-
       tion  to  ccoommpplleettee indicates that the command word is the first non-as-
       signment word on the line, or after a command delimiter such as ;; or ||.
       This usually indicates command name completion.

       If the command word is a full pathname, bbaasshh searches  for  a  compspec
       for  the  full  pathname  first.   If there is no compspec for the full
       pathname, bbaasshh attempts to find a compspec for  the  portion  following
       the  final slash.  If those searches do not result in a compspec, or if
       there is no compspec for the command word, bbaasshh uses any  compspec  de-
       fined  with  the  --DD option to ccoommpplleettee as the default.  If there is no
       default compspec, bbaasshh performs alias expansion on the command word  as
       a  final  resort,  and attempts to find a compspec for the command word
       resulting from any successful expansion.

       If a compspec is not found, bbaasshh performs its default completion as de-
       scribed above under CCoommpplleettiinngg.  Otherwise, once a  compspec  has  been
       found, bbaasshh uses it to generate the list of matching words.

       First,  bbaasshh performs the _a_c_t_i_o_n_s specified by the compspec.  This only
       returns matches which are prefixes of the word being  completed.   When
       the  --ff or --dd option is used for filename or directory name completion,
       bbaasshh uses the shell variable FFIIGGNNOORREE to filter the matches.

       Next, programmable completion generates matches specified by a pathname
       expansion pattern supplied as an argument to the --GG option.  The  words
       generated by the pattern need not match the word being completed.  BBaasshh
       uses  the  FFIIGGNNOORREE variable to filter the matches, but does not use the
       GGLLOOBBIIGGNNOORREE shell variable.

       Next, completion considers the string specified as the argument to  the
       --WW  option.   The string is first split using the characters in the IIFFSS
       special variable as delimiters.  This honors shell quoting  within  the
       string,  in order to provide a mechanism for the words to contain shell
       metacharacters or characters in the value of IIFFSS.  Each  word  is  then
       expanded using brace expansion, tilde expansion, parameter and variable
       expansion, command substitution, and arithmetic expansion, as described
       above under EEXXPPAANNSSIIOONN.  The results are split using the rules described
       above  under  WWoorrdd SSpplliittttiinngg.  The results of the expansion are prefix-
       matched against the word being completed, and the matching words become
       possible completions.

       After these matches have been generated, bbaasshh executes any shell  func-
       tion or command specified with the --FF and --CC options.  When the command
       or   function  is  invoked,  bbaasshh  assigns  values  to  the  CCOOMMPP__LLIINNEE,
       CCOOMMPP__PPOOIINNTT, CCOOMMPP__KKEEYY, and CCOOMMPP__TTYYPPEE variables as described above  under
       SShheellll  VVaarriiaabblleess.  If a shell function is being invoked, bbaasshh also sets
       the CCOOMMPP__WWOORRDDSS and CCOOMMPP__CCWWOORRDD variables.  When the function or  command
       is  invoked,  the  first argument ($$11) is the name of the command whose
       arguments are being completed, the second argument ($$22) is the word be-
       ing completed, and the third argument ($$33) is the  word  preceding  the
       word  being completed on the current command line.  There is no filter-
       ing of the generated completions against the word being completed;  the
       function  or command has complete freedom in generating the matches and
       they do not need to match a prefix of the word.

       Any function specified with --FF is invoked first.  The function may  use
       any of the shell facilities, including the ccoommppggeenn and ccoommppoopptt builtins
       described  below,  to  generate  the matches.  It must put the possible
       completions in the CCOOMMPPRREEPPLLYY array variable, one per array element.

       Next, any command specified with the --CC option is invoked in  an  envi-
       ronment  equivalent to command substitution.  It should print a list of
       completions, one per line, to the standard output.  Backslash will  es-
       cape  a  newline, if necessary.  These are added to the set of possible
       completions.

       After generating all of the possible completions, bbaasshh applies any fil-
       ter specified with the --XX option to the completions in the  list.   The
       filter  is a pattern as used for pathname expansion; a && in the pattern
       is replaced with the text of the word being completed.  A literal && may
       be escaped with a backslash; the backslash is removed before attempting
       a match.  Any completion that matches the pattern is removed  from  the
       list.   A  leading !! negates the pattern; in this case bbaasshh removes any
       completion that does not match the pattern.  If the  nnooccaasseemmaattcchh  shell
       option  is  enabled, bbaasshh performs the match without regard to the case
       of alphabetic characters.

       Finally, programmable completion adds any prefix and  suffix  specified
       with  the  --PP and --SS options, respectively, to each completion, and re-
       turns the result to rreeaaddlliinnee as the list of possible completions.

       If the previously-applied actions do not generate any matches, and  the
       --oo  ddiirrnnaammeess  option was supplied to ccoommpplleettee when the compspec was de-
       fined, bbaasshh attempts directory name completion.

       If the --oo pplluussddiirrss option was supplied to ccoommpplleettee  when  the  compspec
       was  defined,  bbaasshh  attempts  directory  name  completion and adds any
       matches to the set of possible completions.

       By default, if a compspec is found, whatever it generates  is  returned
       to  the  completion  code as the full set of possible completions.  The
       default bbaasshh completions and the rreeaaddlliinnee default of  filename  comple-
       tion  are  disabled.  If the --oo bbaasshhddeeffaauulltt option was supplied to ccoomm--
       pplleettee when the compspec was defined,  and  the  compspec  generates  no
       matches,  bbaasshh  attempts its default completions.  If the compspec and,
       if attempted, the default bbaasshh completions generate no matches, and the
       --oo ddeeffaauulltt option was supplied to ccoommpplleettee when the  compspec  was  de-
       fined, programmable completion performs rreeaaddlliinnee's default completion.

       The  options  supplied to ccoommpplleettee and ccoommppoopptt can control how rreeaaddlliinnee
       treats the completions.  For instance, the _-_o  _f_u_l_l_q_u_o_t_e  option  tells
       rreeaaddlliinnee  to  quote the matches as if they were filenames.  See the de-
       scription of ccoommpplleettee below for details.

       When a compspec indicates that it wants directory name completion,  the
       programmable  completion  functions force rreeaaddlliinnee to append a slash to
       completed names which are symbolic links to directories, subject to the
       value of the mmaarrkk--ddiirreeccttoorriieess rreeaaddlliinnee variable, regardless of the set-
       ting of the mmaarrkk--ssyymmlliinnkkeedd--ddiirreeccttoorriieess rreeaaddlliinnee variable.

       There is some support for dynamically modifying completions.   This  is
       most  useful  when used in combination with a default completion speci-
       fied with ccoommpplleettee --DD.  It's possible for shell functions  executed  as
       completion  functions  to indicate that completion should be retried by
       returning an exit status of 124.  If a shell function returns 124,  and
       changes the compspec associated with the command on which completion is
       being  attempted  (supplied  as the first argument when the function is
       executed), programmable completion restarts from the beginning, with an
       attempt to find a new compspec for that command.  This can be  used  to
       build  a  set  of  completions  dynamically as completion is attempted,
       rather than loading them all at once.

       For instance, assuming that there is a library of compspecs, each  kept
       in  a  file corresponding to the name of the command, the following de-
       fault completion function would load completions dynamically:
              _completion_loader()
              {
                . "/etc/bash_completion.d/$1.sh" \
                  >/dev/null 2>&1 && return 124
              }
              complete -D -F _completion_loader \
                  -o bashdefault -o default

HHIISSTTOORRYY
       When the --oo hhiissttoorryy option to the sseett builtin  is  enabled,  the  shell
       provides access to the _c_o_m_m_a_n_d _h_i_s_t_o_r_y, the list of commands previously
       typed.   The  value  of  the HHIISSTTSSIIZZEE variable is used as the number of
       commands to save in a history list: the shell saves  the  text  of  the
       last HHIISSTTSSIIZZEE commands (default 500).  The shell stores each command in
       the  history list prior to parameter and variable expansion (see EEXXPPAANN--
       SSIIOONN above) but after history expansion is performed,  subject  to  the
       values of the shell variables HHIISSTTIIGGNNOORREE and HHIISSTTCCOONNTTRROOLL.

       On  startup,  bbaasshh  initializes the history list by reading history en-
       tries  from  the  file  named  by  the   HHIISSTTFFIILLEE   variable   (default
       _~_/_._b_a_s_h___h_i_s_t_o_r_y).   That  file is referred to as the _h_i_s_t_o_r_y _f_i_l_e.  The
       history file is truncated, if necessary, to contain no  more  than  the
       number  of  history  entries specified by the value of the HHIISSTTFFIILLEESSIIZZEE
       variable.  If HHIISSTTFFIILLEESSIIZZEE is unset, or  set  to  null,  a  non-numeric
       value, or a numeric value less than zero, the history file is not trun-
       cated.

       When the history file is read, lines beginning with the history comment
       character followed immediately by a digit are interpreted as timestamps
       for  the  following history line.  These timestamps are optionally dis-
       played depending on the value of  the  HHIISSTTTTIIMMEEFFOORRMMAATT  variable.   When
       present,  history timestamps delimit history entries, making multi-line
       entries possible.

       When a shell with history enabled exits, bbaasshh copies the last $$HHIISSTTSSIIZZEE
       entries from the history list to $$HHIISSTTFFIILLEE.  If  the  hhiissttaappppeenndd  shell
       option  is  enabled  (see  the description of sshhoopptt under SSHHEELLLL BBUUIILLTTIINN
       CCOOMMMMAANNDDSS below), bbaasshh appends the entries to the history  file,  other-
       wise  it overwrites the history file.  If HHIISSTTFFIILLEE is unset or null, or
       if the history file is unwritable, the history  is  not  saved.   After
       saving  the history, bbaasshh truncates the history file to contain no more
       than HHIISSTTFFIILLEESSIIZZEE lines as described above.

       If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is set, the shell writes  the  timestamp
       information  associated  with  each  history entry to the history file,
       marked with the history comment character, so timestamps are  preserved
       across shell sessions.  This uses the history comment character to dis-
       tinguish  timestamps  from  other  history lines.  As above, when using
       HHIISSTTTTIIMMEEFFOORRMMAATT, the timestamps delimit multi-line history entries.

       The ffcc builtin command (see SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS below) will list  or
       edit and re-execute a portion of the history list.  The hhiissttoorryy builtin
       can display or modify the history list and manipulate the history file.
       When  using command-line editing, search commands are available in each
       editing mode that provide access to the history list.

       The shell allows control over which commands are saved on  the  history
       list.  The HHIISSTTCCOONNTTRROOLL and HHIISSTTIIGGNNOORREE variables are used to save only a
       subset  of  the  commands  entered.  If the ccmmddhhiisstt shell option is en-
       abled, the shell attempts to save each line of a multi-line command  in
       the  same  history entry, adding semicolons where necessary to preserve
       syntactic correctness.  The lliitthhiisstt shell option  modifies  ccmmddhhiisstt  by
       saving  the  command with embedded newlines instead of semicolons.  See
       the description of the sshhoopptt builtin below under SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
       for information on setting and unsetting shell options.

HHIISSTTOORRYY EEXXPPAANNSSIIOONN
       The shell supports a history expansion feature that is similar  to  the
       history  expansion in ccsshh.  This section describes what syntax features
       are available.

       History expansion is enabled by default for interactive shells, and can
       be disabled using the ++HH option to the sseett builtin command  (see  SSHHEELLLL
       BBUUIILLTTIINN CCOOMMMMAANNDDSS below).  Non-interactive shells do not perform history
       expansion by default, but it can be enabled with "set -H".

       History expansions introduce words from the history list into the input
       stream,  making  it  easy to repeat commands, insert the arguments to a
       previous command into the current input line, or fix errors in previous
       commands quickly.

       History expansion is performed immediately after  a  complete  line  is
       read,  before  the shell breaks it into words, and is performed on each
       line individually.  The shell attempts to inform the history  expansion
       functions about quoting still in effect from previous lines.

       It  takes  place in two parts.  The first is to determine which history
       list entry to use during substitution.  The second is  to  select  por-
       tions of that entry to include into the current one.

       The  entry  selected from the history is the _e_v_e_n_t, and the portions of
       that entry that are acted upon are _w_o_r_d_s.  Various _m_o_d_i_f_i_e_r_s are avail-
       able to manipulate the selected words.  The entry is split  into  words
       in  the same fashion as when reading input, so that several _m_e_t_a_c_h_a_r_a_c_-
       _t_e_r-separated words surrounded by quotes are considered one word.   The
       _e_v_e_n_t  _d_e_s_i_g_n_a_t_o_r  selects  the event, the optional _w_o_r_d _d_e_s_i_g_n_a_t_o_r se-
       lects words from the event, and various optional _m_o_d_i_f_i_e_r_s  are  avail-
       able to manipulate the selected words.

       History  expansions are introduced by the appearance of the history ex-
       pansion character, which is !! by default.  History expansions  may  ap-
       pear anywhere in the input, but do not nest.

       Only  backslash  (\\)  and single quotes can quote the history expansion
       character, but the history  expansion  character  is  also  treated  as
       quoted if it immediately precedes the closing double quote in a double-
       quoted string.

       Several  characters inhibit history expansion if found immediately fol-
       lowing the history expansion character, even if it is unquoted:  space,
       tab,  newline,  carriage  return, ==, and the other shell metacharacters
       defined above.

       There is a special abbreviation for substitution, active when the _q_u_i_c_k
       _s_u_b_s_t_i_t_u_t_i_o_n character (described above under hhiissttcchhaarrss) is  the  first
       character on the line.  It selects the previous history list entry, us-
       ing  an  event  designator equivalent to !!!!, and substitutes one string
       for another in that entry.  It is described below under EEvveenntt  DDeessiiggnnaa--
       ttoorrss.   This is the only history expansion that does not begin with the
       history expansion character.

       Several shell options settable with the sshhoopptt builtin will modify  his-
       tory  expansion  behavior (see the description of the sshhoopptt builtin be-
       low).and If the hhiissttvveerriiffyy shell option is enabled, and rreeaaddlliinnee is be-
       ing used, history substitutions are not immediately passed to the shell
       parser.  Instead, the expanded line is reloaded into the rreeaaddlliinnee edit-
       ing buffer for further modification.  If rreeaaddlliinnee is  being  used,  and
       the  hhiissttrreeeeddiitt  shell option is enabled, a failed history substitution
       is reloaded into the rreeaaddlliinnee editing buffer for correction.

       The --pp option to the hhiissttoorryy builtin command shows what a  history  ex-
       pansion  will do before using it.  The --ss option to the hhiissttoorryy builtin
       will add commands to the end of the history list without actually  exe-
       cuting them, so that they are available for subsequent recall.

       The  shell allows control of the various characters used by the history
       expansion mechanism (see the description of hhiissttcchhaarrss above under SShheellll
       VVaarriiaabblleess).  The shell uses the history comment character to mark  his-
       tory timestamps when writing the history file.

   EEvveenntt DDeessiiggnnaattoorrss
       An  event  designator  is  a reference to an entry in the history list.
       The event designator consists of the portion of the word beginning with
       the history expansion character and ending with the word designator  if
       present,  or  the  end  of the word.  Unless the reference is absolute,
       events are relative to the current position in the history list.

       !!      Start a history substitution, except when followed by  a  bbllaannkk,
              newline,  carriage  return, =, or, when the eexxttgglloobb shell option
              is enabled using the sshhoopptt builtin, (.
       !!_n     Refer to history list entry _n.
       !!--_n    Refer to the current entry minus _n.
       !!!!     Refer to the previous entry.  This is a synonym for "!-1".
       !!_s_t_r_i_n_g
              Refer to the most recent command preceding the current  position
              in the history list starting with _s_t_r_i_n_g.
       !!??_s_t_r_i_n_g[[??]]
              Refer  to the most recent command preceding the current position
              in the history list containing _s_t_r_i_n_g.  The trailing  ??  may  be
              omitted  if  _s_t_r_i_n_g  is  followed  immediately by a newline.  If
              _s_t_r_i_n_g is missing, this uses the string  from  the  most  recent
              search; it is an error if there is no previous search string.
       ^^_s_t_r_i_n_g_1^^_s_t_r_i_n_g_2^^
              Quick  substitution.   Repeat  the  previous  command, replacing
              _s_t_r_i_n_g_1 with  _s_t_r_i_n_g_2.   Equivalent  to  "!!:s^_s_t_r_i_n_g_1^_s_t_r_i_n_g_2^"
              (see MMooddiiffiieerrss below).
       !!##     The entire command line typed so far.

   WWoorrdd DDeessiiggnnaattoorrss
       Word designators are used to select desired words from the event.  They
       are optional; if the word designator isn't supplied, the history expan-
       sion uses the entire event.  A :: separates the event specification from
       the  word  designator.  It may be omitted if the word designator begins
       with a ^^, $$, **, --, or %%.  Words are numbered from the beginning of  the
       line,  with  the  first  word being denoted by 0 (zero).  Words are in-
       serted into the current line separated by single spaces.

       00 ((zzeerroo))
              The zeroth word.  For the shell, this is the command word.
       _n      The _nth word.
       ^^      The first argument: word 1.
       $$      The last word.  This is usually the last argument, but will  ex-
              pand to the zeroth word if there is only one word in the line.
       %%      The first word matched by the most recent "?_s_t_r_i_n_g?"  search, if
              the  search  string  begins  with  a character that is part of a
              word.  By default, searches begin at the end of  each  line  and
              proceed  to  the beginning, so the first word matched is the one
              closest to the end of the line.
       _x--_y    A range of words; "-_y" abbreviates "0-_y".
       **      All of the words but the zeroth.  This is a synonym  for  "_1_-_$".
              It  is  not  an  error to use ** if there is just one word in the
              event; it expands to the empty string in that case.
       xx**     Abbreviates _x_-_$.
       xx--     Abbreviates _x_-_$ like xx**, but omits the last word.  If xx is miss-
              ing, it defaults to 0.

       If a word designator is supplied without an  event  specification,  the
       previous command is used as the event, equivalent to !!!!.

   MMooddiiffiieerrss
       After  the  optional  word  designator, the expansion may include a se-
       quence of one or more of the following modifiers, each  preceded  by  a
       ":".   These  modify, or edit, the word or words selected from the his-
       tory event.

       hh      Remove a trailing pathname component, leaving only the head.
       tt      Remove all leading pathname components, leaving the tail.
       rr      Remove a trailing suffix of the form _._x_x_x, leaving the basename.
       ee      Remove all but the trailing suffix.
       pp      Print the new command but do not execute it.
       qq      Quote the substituted words, escaping further substitutions.
       xx      Quote the substituted words as with qq, but break into  words  at
              bbllaannkkss  and newlines.  The qq and xx modifiers are mutually exclu-
              sive; expansion uses the last one supplied.
       ss//_o_l_d//_n_e_w//
              Substitute _n_e_w for the first occurrence  of  _o_l_d  in  the  event
              line.  Any character may be used as the delimiter in place of /.
              The  final  delimiter is optional if it is the last character of
              the event line.  A single backslash quotes the delimiter in  _o_l_d
              and  _n_e_w.  If & appears in _n_e_w, it is replaced with _o_l_d.  A sin-
              gle backslash quotes the &.  If _o_l_d is null, it is  set  to  the
              last  _o_l_d  substituted, or, if no previous history substitutions
              took place, the last _s_t_r_i_n_g in a !!??_s_t_r_i_n_g[[??]]  search.  If _n_e_w is
              null, each matching _o_l_d is deleted.
       &&      Repeat the previous substitution.
       gg      Cause changes to be applied over the entire event line.  This is
              used in conjunction with "::ss" (e.g.,  "::ggss//_o_l_d//_n_e_w//")  or  "::&&".
              If  used with "::ss", any delimiter can be used in place of /, and
              the final delimiter is optional if it is the last  character  of
              the event line.  An aa may be used as a synonym for gg.
       GG      Apply the following "ss" or "&&" modifier once to each word in the
              event line.

SSHHEELLLL BBUUIILLTTIINN CCOOMMMMAANNDDSS
       Unless otherwise noted, each builtin command documented in this section
       as accepting options preceded by -- accepts ---- to signify the end of the
       options.  The ::, ttrruuee, ffaallssee, and tteesstt/[[ builtins do not accept options
       and  do  not treat ---- specially.  The eexxiitt, llooggoouutt, rreettuurrnn, bbrreeaakk, ccoonn--
       ttiinnuuee, lleett, and sshhiifftt builtins accept and process  arguments  beginning
       with  -- without requiring ----.  Other builtins that accept arguments but
       are not specified as accepting options  interpret  arguments  beginning
       with  --  as  invalid options and require ---- to prevent this interpreta-
       tion.

       :: [_a_r_g_u_m_e_n_t_s]
              No effect; the command does nothing beyond  expanding  _a_r_g_u_m_e_n_t_s
              and performing any specified redirections.  The return status is
              zero.

       .. [--pp _p_a_t_h] _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
       ssoouurrccee [--pp _p_a_t_h] _f_i_l_e_n_a_m_e [_a_r_g_u_m_e_n_t_s]
              The  .. command (ssoouurrccee) reads and execute commands from _f_i_l_e_n_a_m_e
              in the current shell environment and returns the exit status  of
              the last command executed from _f_i_l_e_n_a_m_e.

              If _f_i_l_e_n_a_m_e does not contain a slash, .. searches for it.  If the
              --pp  option  is supplied, .. treats _p_a_t_h as a colon-separated list
              of directories in which to find _f_i_l_e_n_a_m_e; otherwise, .. uses  the
              entries  in  PPAATTHH  to  find  the  directory containing _f_i_l_e_n_a_m_e.
              _f_i_l_e_n_a_m_e does not need to be executable.  When bbaasshh  is  not  in
              posix mode, it searches the current directory if _f_i_l_e_n_a_m_e is not
              found  in  PPAATTHH, but does not search the current directory if --pp
              is supplied.  If the ssoouurrcceeppaatthh option to the sshhoopptt builtin com-
              mand is turned off, .. does not search PPAATTHH.

              If any _a_r_g_u_m_e_n_t_s are supplied, they become the positional  para-
              meters  when _f_i_l_e_n_a_m_e is executed.  Otherwise the positional pa-
              rameters are unchanged.

              If the --TT option is enabled, .. inherits any trap on DDEEBBUUGG; if it
              is not, any DDEEBBUUGG trap string is saved and restored  around  the
              call to .., and .. unsets the DDEEBBUUGG trap while it executes.  If --TT
              is not set, and the sourced file changes the DDEEBBUUGG trap, the new
              value persists after .. completes.  The return status is the sta-
              tus of the last command executed from _f_i_l_e_n_a_m_e (0 if no commands
              are  executed),  and non-zero if _f_i_l_e_n_a_m_e is not found or cannot
              be read.

       aalliiaass [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
              With no arguments or with the --pp option, aalliiaass prints  the  list
              of  aliases  in  the  form  aalliiaass _n_a_m_e=_v_a_l_u_e on standard output.
              When arguments are supplied, define an alias for each _n_a_m_e whose
              _v_a_l_u_e is given.  A trailing space in _v_a_l_u_e causes the next  word
              to  be checked for alias substitution when the alias is expanded
              during command parsing.  For each _n_a_m_e in the argument list  for
              which  no  _v_a_l_u_e  is  supplied,  print the name and value of the
              alias _n_a_m_e.  aalliiaass returns true unless a _n_a_m_e is given  (without
              a corresponding =_v_a_l_u_e) for which no alias has been defined.

       bbgg [_j_o_b_s_p_e_c ...]
              Resume  each  suspended  job _j_o_b_s_p_e_c in the background, as if it
              had been started with &&.  If _j_o_b_s_p_e_c is not present,  the  shell
              uses its notion of the _c_u_r_r_e_n_t _j_o_b.  bbgg _j_o_b_s_p_e_c returns 0 unless
              run  when  job control is disabled or, when run with job control
              enabled, any specified _j_o_b_s_p_e_c was  not  found  or  was  started
              without job control.

       bbiinndd [--mm _k_e_y_m_a_p] [--llssvvSSVVXX]
       bbiinndd [--mm _k_e_y_m_a_p] [--qq _f_u_n_c_t_i_o_n] [--uu _f_u_n_c_t_i_o_n] [--rr _k_e_y_s_e_q]
       bbiinndd [--mm _k_e_y_m_a_p] --ff _f_i_l_e_n_a_m_e
       bbiinndd [--mm _k_e_y_m_a_p] --xx _k_e_y_s_e_q[:] _s_h_e_l_l_-_c_o_m_m_a_n_d
       bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_f_u_n_c_t_i_o_n_-_n_a_m_e
       bbiinndd [--mm _k_e_y_m_a_p] --pp|--PP [_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d]
       bbiinndd [--mm _k_e_y_m_a_p] _k_e_y_s_e_q:_r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d
       bbiinndd _r_e_a_d_l_i_n_e_-_c_o_m_m_a_n_d_-_l_i_n_e
              Display  current  rreeaaddlliinnee key and function bindings, bind a key
              sequence to a rreeaaddlliinnee function or macro or to a shell  command,
              or  set  a rreeaaddlliinnee variable.  Each non-option argument is a key
              binding or command as it would appear in a rreeaaddlliinnee  initializa-
              tion  file such as _._i_n_p_u_t_r_c, but each binding or command must be
              passed   as   a   separate    argument;    e.g.,    '"\C-x\C-r":
              re-read-init-file'.    In  the  following  descriptions,  output
              available to be re-read is formatted as commands that would  ap-
              pear in a rreeaaddlliinnee initialization file or that would be supplied
              as  individual  arguments  to  a bbiinndd command.  Options, if sup-
              plied, have the following meanings:
              --mm _k_e_y_m_a_p
                     Use _k_e_y_m_a_p as the keymap to be affected by the subsequent
                     bindings.  Acceptable _k_e_y_m_a_p names are _e_m_a_c_s_, _e_m_a_c_s_-_s_t_a_n_-
                     _d_a_r_d_, _e_m_a_c_s_-_m_e_t_a_, _e_m_a_c_s_-_c_t_l_x_,  _v_i_,  _v_i_-_m_o_v_e_,  _v_i_-_c_o_m_m_a_n_d,
                     and  _v_i_-_i_n_s_e_r_t.   _v_i is equivalent to _v_i_-_c_o_m_m_a_n_d (_v_i_-_m_o_v_e
                     is also a synonym); _e_m_a_c_s is  equivalent  to  _e_m_a_c_s_-_s_t_a_n_-
                     _d_a_r_d.
              --ll     List the names of all rreeaaddlliinnee functions.
              --pp     Display  rreeaaddlliinnee  function  names and bindings in such a
                     way that they can be used as an argument to a  subsequent
                     bbiinndd  command  or  in a rreeaaddlliinnee initialization file.  If
                     arguments remain after  option  processing,  bbiinndd  treats
                     them  as  rreeaaddlliinnee  command names and restricts output to
                     those names.
              --PP     List current rreeaaddlliinnee function names  and  bindings.   If
                     arguments  remain  after  option  processing, bbiinndd treats
                     them as rreeaaddlliinnee command names and  restricts  output  to
                     those names.
              --ss     Display  rreeaaddlliinnee  key  sequences bound to macros and the
                     strings they output in such a way that they can  be  used
                     as an argument to a subsequent bbiinndd command or in a rreeaadd--
                     lliinnee initialization file.
              --SS     Display  rreeaaddlliinnee  key  sequences bound to macros and the
                     strings they output.
              --vv     Display rreeaaddlliinnee variable names and values in such a  way
                     that they can be used as an argument to a subsequent bbiinndd
                     command or in a rreeaaddlliinnee initialization file.
              --VV     List current rreeaaddlliinnee variable names and values.
              --ff _f_i_l_e_n_a_m_e
                     Read key bindings from _f_i_l_e_n_a_m_e.
              --qq _f_u_n_c_t_i_o_n
                     Display  key  sequences  that  invoke  the named rreeaaddlliinnee
                     _f_u_n_c_t_i_o_n.
              --uu _f_u_n_c_t_i_o_n
                     Unbind all key sequences  bound  to  the  named  rreeaaddlliinnee
                     _f_u_n_c_t_i_o_n.
              --rr _k_e_y_s_e_q
                     Remove any current binding for _k_e_y_s_e_q.
              --xx _k_e_y_s_e_q[[:: ]]_s_h_e_l_l_-_c_o_m_m_a_n_d
                     Cause _s_h_e_l_l_-_c_o_m_m_a_n_d to be executed whenever _k_e_y_s_e_q is en-
                     tered.  The separator between _k_e_y_s_e_q and _s_h_e_l_l_-_c_o_m_m_a_n_d is
                     either  whitespace  or  a  colon  optionally  followed by
                     whitespace.  If the separator is  whitespace,  _s_h_e_l_l_-_c_o_m_-
                     _m_a_n_d  must  be enclosed in double quotes and rreeaaddlliinnee ex-
                     pands any of its special backslash-escapes in  _s_h_e_l_l_-_c_o_m_-
                     _m_a_n_d  before saving it.  If the separator is a colon, any
                     enclosing double quotes are optional, and  rreeaaddlliinnee  does
                     not  expand  the  command string before saving it.  Since
                     the entire key binding expression must be a single  argu-
                     ment,  it  should  be  enclosed  in  single quotes.  When
                     _s_h_e_l_l_-_c_o_m_m_a_n_d is  executed,  the  shell  sets  the  RREEAADD--
                     LLIINNEE__LLIINNEE  variable  to the contents of the rreeaaddlliinnee line
                     buffer and the RREEAADDLLIINNEE__PPOOIINNTT and RREEAADDLLIINNEE__MMAARRKK variables
                     to the current location of the insertion  point  and  the
                     saved  insertion  point  (the  mark),  respectively.  The
                     shell assigns any numeric argument the user  supplied  to
                     the  RREEAADDLLIINNEE__AARRGGUUMMEENNTT  variable.   If there was no argu-
                     ment, that variable is not set.  If the executed  command
                     changes   the   value  of  any  of  RREEAADDLLIINNEE__LLIINNEE,  RREEAADD--
                     LLIINNEE__PPOOIINNTT, or RREEAADDLLIINNEE__MMAARRKK, those new  values  will  be
                     reflected in the editing state.
              --XX     List  all  key  sequences bound to shell commands and the
                     associated commands in a format that can be reused as  an
                     argument to a subsequent bbiinndd command.

              The  return value is 0 unless an unrecognized option is supplied
              or an error occurred.

       bbrreeaakk [_n]
              Exit from within a ffoorr, wwhhiillee, uunnttiill, or sseelleecctt loop.  If  _n  is
              specified, bbrreeaakk exits _n enclosing loops.  _n must be >= 1.  If _n
              is  greater  than  the  number of enclosing loops, all enclosing
              loops are exited.  The return value is 0 unless _n is not greater
              than or equal to 1.

       bbuuiillttiinn _s_h_e_l_l_-_b_u_i_l_t_i_n [_a_r_g_u_m_e_n_t_s]
              Execute the specified shell builtin  _s_h_e_l_l_-_b_u_i_l_t_i_n,  passing  it
              _a_r_g_u_m_e_n_t_s,  and  return  its  exit  status.  This is useful when
              defining a function whose name is the same as a  shell  builtin,
              retaining  the functionality of the builtin within the function.
              The ccdd builtin is commonly redefined this way.  The return  sta-
              tus is false if _s_h_e_l_l_-_b_u_i_l_t_i_n is not a shell builtin command.

       ccaalllleerr [_e_x_p_r]
              Returns the context of any active subroutine call (a shell func-
              tion or a script executed with the .. or ssoouurrccee builtins).

              Without  _e_x_p_r,  ccaalllleerr displays the line number and source file-
              name of the current subroutine call.  If a non-negative  integer
              is supplied as _e_x_p_r, ccaalllleerr displays the line number, subroutine
              name, and source file corresponding to that position in the cur-
              rent  execution call stack.  This extra information may be used,
              for example, to print a stack trace.  The current frame is frame
              0.

              The return value is 0 unless the shell is not executing  a  sub-
              routine  call or _e_x_p_r does not correspond to a valid position in
              the call stack.

       ccdd [--LL] [--@@] [_d_i_r]
       ccdd --PP [--ee] [--@@] [_d_i_r]
              Change the current directory to _d_i_r.  if _d_i_r  is  not  supplied,
              the  value of the HHOOMMEE shell variable is used as _d_i_r.  The vari-
              able CCDDPPAATTHH exists, and _d_i_r does not begin with a slash (/),  ccdd
              uses it as a search path: the shell searches each directory name
              in  CCDDPPAATTHH  for  _d_i_r.  Alternative directory names in CCDDPPAATTHH are
              separated by a colon (:).  A null directory name  in  CCDDPPAATTHH  is
              the same as the current directory, i.e., ".".

              The  --PP option causes ccdd to use the physical directory structure
              by resolving symbolic links while traversing _d_i_r and before pro-
              cessing instances of _._. in _d_i_r (see also the --PP  option  to  the
              sseett builtin command).

              The  --LL  option  forces ccdd to follow symbolic links by resolving
              the link after processing instances of _._. in _d_i_r.  If _._. appears
              in _d_i_r, ccdd processes it by  removing  the  immediately  previous
              pathname component from _d_i_r, back to a slash or the beginning of
              _d_i_r,  and  verifying that the portion of _d_i_r it has processed to
              that point is still a valid directory name  after  removing  the
              pathname component.  If it is not a valid directory name, ccdd re-
              turns  a  non-zero status.  If neither --LL nor --PP is supplied, ccdd
              behaves as if --LL had been supplied.

              If the --ee option is supplied with --PP, and ccdd cannot successfully
              determine the current working directory after a  successful  di-
              rectory change, it returns a non-zero status.

              On  systems that support it, the --@@ option presents the extended
              attributes associated with a file as a directory.

              An argument of -- is converted to $$OOLLDDPPWWDD before  attempting  the
              directory change.

              If  ccdd  uses  a non-empty directory name from CCDDPPAATTHH, or if -- is
              the first argument, and the directory change is  successful,  ccdd
              writes the absolute pathname of the new working directory to the
              standard output.

              If  the directory change is successful, ccdd sets the value of the
              PPWWDD environment variable to the new directory name, and sets the
              OOLLDDPPWWDD environment variable to the value of the current  working
              directory before the change.

              The  return  value  is  true  if  the directory was successfully
              changed; false otherwise.

       ccoommmmaanndd [--ppVVvv] _c_o_m_m_a_n_d [_a_r_g ...]
              The ccoommmmaanndd builtin runs _c_o_m_m_a_n_d with _a_r_g_s suppressing the  nor-
              mal shell function lookup for _c_o_m_m_a_n_d.  Only builtin commands or
              commands  found  in the PPAATTHH named _c_o_m_m_a_n_d are executed.  If the
              --pp option is supplied, the search for _c_o_m_m_a_n_d is performed using
              a default value for PPAATTHH that is guaranteed to find all  of  the
              standard utilities.

              If  either the --VV or --vv option is supplied, ccoommmmaanndd prints a de-
              scription of _c_o_m_m_a_n_d.  The --vv option displays a single word  in-
              dicating  the command or filename used to invoke _c_o_m_m_a_n_d; the --VV
              option produces a more verbose description.

              If the --VV or --vv option is supplied, the exit status is  zero  if
              _c_o_m_m_a_n_d  was  found,  and non-zero if not.  If neither option is
              supplied and an error occurred or _c_o_m_m_a_n_d cannot be  found,  the
              exit  status  is 127.  Otherwise, the exit status of the ccoommmmaanndd
              builtin is the exit status of _c_o_m_m_a_n_d.

       ccoommppggeenn [--VV _v_a_r_n_a_m_e] [_o_p_t_i_o_n] [_w_o_r_d]
              Generate possible completion matches for _w_o_r_d according  to  the
              _o_p_t_i_o_ns,  which  may  be  any  option  accepted  by the ccoommpplleettee
              builtin with the exceptions of --pp, --rr, --DD, --EE, and --II, and write
              the matches to the standard output.

              If the --VV option is supplied, ccoommppggeenn stores the generated  com-
              pletions  into  the  indexed  array  variable _v_a_r_n_a_m_e instead of
              writing them to the standard output.

              When using the --FF or --CC options, the various shell variables set
              by the programmable completion facilities, while available, will
              not have useful values.

              The matches will be generated in the same way as if the program-
              mable completion code had generated them directly from a comple-
              tion specification with the same flags.  If _w_o_r_d  is  specified,
              only  those  completions  matching  _w_o_r_d  will  be  displayed or
              stored.

              The return value is true unless an invalid option  is  supplied,
              or no matches were generated.

       ccoommpplleettee [--aabbccddeeffggjjkkssuuvv] [--oo _c_o_m_p_-_o_p_t_i_o_n] [--DDEEII] [--AA _a_c_t_i_o_n]
              [--GG _g_l_o_b_p_a_t] [--WW _w_o_r_d_l_i_s_t] [--FF _f_u_n_c_t_i_o_n] [--CC _c_o_m_m_a_n_d]
              [--XX _f_i_l_t_e_r_p_a_t] [--PP _p_r_e_f_i_x] [--SS _s_u_f_f_i_x] _n_a_m_e [_n_a_m_e ...]
       ccoommpplleettee --pprr [--DDEEII] [_n_a_m_e ...]
              Specify how arguments to each _n_a_m_e should be completed.

              If the --pp option is supplied, or if no options or _n_a_m_es are sup-
              plied,  print  existing  completion specifications in a way that
              allows them to be reused as input.  The --rr option removes a com-
              pletion specification for each _n_a_m_e, or, if no  _n_a_m_es  are  sup-
              plied, all completion specifications.

              The  --DD option indicates that other supplied options and actions
              should apply to the "default" command completion; that is,  com-
              pletion  attempted on a command for which no completion has pre-
              viously been defined.  The --EE option indicates that  other  sup-
              plied  options  and actions should apply to "empty" command com-
              pletion; that is, completion attempted on a blank line.  The  --II
              option  indicates that other supplied options and actions should
              apply to completion on the initial non-assignment  word  on  the
              line, or after a command delimiter such as ;; or ||, which is usu-
              ally command name completion.  If multiple options are supplied,
              the --DD option takes precedence over --EE, and both take precedence
              over  --II.   If any of --DD, --EE, or --II are supplied, any other _n_a_m_e
              arguments are ignored; these completions only apply to the  case
              specified by the option.

              The process of applying these completion specifications when at-
              tempting  word completion  is described above under PPrrooggrraammmmaabbllee
              CCoommpplleettiioonn.

              Other options, if specified, have the following  meanings.   The
              arguments  to the --GG, --WW, and --XX options (and, if necessary, the
              --PP and --SS options) should be quoted to protect them from  expan-
              sion before the ccoommpplleettee builtin is invoked.

              --oo _c_o_m_p_-_o_p_t_i_o_n
                      The  _c_o_m_p_-_o_p_t_i_o_n  controls  several aspects of the comp-
                      spec's behavior beyond the simple generation of  comple-
                      tions.  _c_o_m_p_-_o_p_t_i_o_n may be one of:
                      bbaasshhddeeffaauulltt
                              Perform the rest of the default bbaasshh completions
                              if the compspec generates no matches.
                      ddeeffaauulltt Use  rreeaaddlliinnee's  default  filename completion if
                              the compspec generates no matches.
                      ddiirrnnaammeess
                              Perform directory name completion if  the  comp-
                              spec generates no matches.
                      ffiilleennaammeess
                              Tell  rreeaaddlliinnee that the compspec generates file-
                              names, so it can perform  any  filename-specific
                              processing  (such as adding a slash to directory
                              names, quoting special characters, or  suppress-
                              ing  trailing  spaces).   This is intended to be
                              used with shell functions.
                      ffuullllqquuoottee
                              Tell rreeaaddlliinnee to quote all the  completed  words
                              even if they are not filenames.
                      nnooqquuoottee Tell  rreeaaddlliinnee  not to quote the completed words
                              if they are filenames (quoting filenames is  the
                              default).
                      nnoossoorrtt  Tell  rreeaaddlliinnee  not to sort the list of possible
                              completions alphabetically.
                      nnoossppaaccee Tell rreeaaddlliinnee not to append  a  space  (the  de-
                              fault)  to  words  completed  at  the end of the
                              line.
                      pplluussddiirrss
                              After generating  any  matches  defined  by  the
                              compspec,  attempt directory name completion and
                              add any matches to the results of the other  ac-
                              tions.
              --AA _a_c_t_i_o_n
                      The  _a_c_t_i_o_n  may  be  one of the following to generate a
                      list of possible completions:
                      aalliiaass   Alias names.  May also be specified as --aa.
                      aarrrraayyvvaarr
                              Array variable names.
                      bbiinnddiinngg RReeaaddlliinnee key binding names.
                      bbuuiillttiinn Names of shell builtin commands.   May  also  be
                              specified as --bb.
                      ccoommmmaanndd Command names.  May also be specified as --cc.
                      ddiirreeccttoorryy
                              Directory names.  May also be specified as --dd.
                      ddiissaabblleedd
                              Names of disabled shell builtins.
                      eennaabblleedd Names of enabled shell builtins.
                      eexxppoorrtt  Names  of exported shell variables.  May also be
                              specified as --ee.
                      ffiillee    File and directory names, similar to  rreeaaddlliinnee's
                              filename  completion.   May also be specified as
                              --ff.
                      ffuunnccttiioonn
                              Names of shell functions.
                      ggrroouupp   Group names.  May also be specified as --gg.
                      hheellppttooppiicc
                              Help topics as accepted by the hheellpp builtin.
                      hhoossttnnaammee
                              Hostnames, as taken from the file  specified  by
                              the HHOOSSTTFFIILLEE shell variable.
                      jjoobb     Job  names,  if job control is active.  May also
                              be specified as --jj.
                      kkeeyywwoorrdd Shell reserved words.  May also be specified  as
                              --kk.
                      rruunnnniinngg Names of running jobs, if job control is active.
                      sseerrvviiccee Service names.  May also be specified as --ss.
                      sseettoopptt  Valid  arguments  for  the  --oo option to the sseett
                              builtin.
                      sshhoopptt   Shell option names  as  accepted  by  the  sshhoopptt
                              builtin.
                      ssiiggnnaall  Signal names.
                      ssttooppppeedd Names of stopped jobs, if job control is active.
                      uusseerr    User names.  May also be specified as --uu.
                      vvaarriiaabbllee
                              Names of all shell variables.  May also be spec-
                              ified as --vv.
              --CC _c_o_m_m_a_n_d
                      _c_o_m_m_a_n_d  is  executed in a subshell environment, and its
                      output is used as the possible  completions.   Arguments
                      are passed as with the --FF option.
              --FF _f_u_n_c_t_i_o_n
                      The  shell  function _f_u_n_c_t_i_o_n is executed in the current
                      shell environment.  When the function is  executed,  the
                      first argument ($$11) is the name of the command whose ar-
                      guments are being completed, the second argument ($$22) is
                      the word being completed, and the third argument ($$33) is
                      the  word preceding the word being completed on the cur-
                      rent command line.  When _f_u_n_c_t_i_o_n finishes, programmable
                      completion retrieves the possible completions  from  the
                      value of the CCOOMMPPRREEPPLLYY array variable.
              --GG _g_l_o_b_p_a_t
                      Expand  the pathname expansion pattern _g_l_o_b_p_a_t to gener-
                      ate the possible completions.
              --PP _p_r_e_f_i_x
                      Add _p_r_e_f_i_x to the beginning of each possible  completion
                      after all other options have been applied.
              --SS _s_u_f_f_i_x
                      Append  _s_u_f_f_i_x  to  each  possible  completion after all
                      other options have been applied.
              --WW _w_o_r_d_l_i_s_t
                      Split the _w_o_r_d_l_i_s_t using the characters in the IIFFSS  spe-
                      cial  variable  as delimiters, and expand each resulting
                      word.  Shell quoting is honored within _w_o_r_d_l_i_s_t, in  or-
                      der  to  provide  a  mechanism  for the words to contain
                      shell metacharacters or characters in the value of  IIFFSS.
                      The  possible  completions are the members of the resul-
                      tant list which match a prefix of the  word  being  com-
                      pleted.
              --XX _f_i_l_t_e_r_p_a_t
                      _f_i_l_t_e_r_p_a_t  is  a pattern as used for pathname expansion.
                      It is applied to the list of possible completions gener-
                      ated by the preceding options and  arguments,  and  each
                      completion  matching _f_i_l_t_e_r_p_a_t is removed from the list.
                      A leading !! in _f_i_l_t_e_r_p_a_t negates the  pattern;  in  this
                      case, any completion not matching _f_i_l_t_e_r_p_a_t is removed.

              The  return  value is true unless an invalid option is supplied,
              an option other than --pp, --rr, --DD, --EE, or --II is supplied without a
              _n_a_m_e argument, an attempt is made to remove a completion  speci-
              fication for a _n_a_m_e for which no specification exists, or an er-
              ror occurs adding a completion specification.

       ccoommppoopptt [--oo _o_p_t_i_o_n] [--DDEEII] [++oo _o_p_t_i_o_n] [_n_a_m_e]
              Modify  completion  options  for  each _n_a_m_e according to the _o_p_-
              _t_i_o_ns, or for the currently-executing completion if no _n_a_m_es are
              supplied.  If no _o_p_t_i_o_ns are supplied,  display  the  completion
              options  for  each _n_a_m_e or the current completion.  The possible
              values of _o_p_t_i_o_n are those valid for the  ccoommpplleettee  builtin  de-
              scribed above.

              The --DD option indicates that other supplied options should apply
              to  the  "default"  command  completion; the --EE option indicates
              that other supplied options should apply to "empty" command com-
              pletion; and the --II option indicates that other supplied options
              should apply to completion on the  initial  word  on  the  line.
              These are determined in the same way as the ccoommpplleettee builtin.

              If multiple options are supplied, the --DD option takes precedence
              over --EE, and both take precedence over --II.

              The  return  value is true unless an invalid option is supplied,
              an attempt is made to modify the options for a _n_a_m_e for which no
              completion specification exists, or an output error occurs.

       ccoonnttiinnuuee [_n]
              ccoonnttiinnuuee resumes the next iteration of the enclosing ffoorr, wwhhiillee,
              uunnttiill, or sseelleecctt loop.  If _n is specified, bbaasshh resumes the  _nth
              enclosing  loop.  _n must be >= 1.  If _n is greater than the num-
              ber of enclosing loops, the shell  resumes  the  last  enclosing
              loop  (the "top-level" loop).  The return value is 0 unless _n is
              not greater than or equal to 1.

       ddeeccllaarree [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
       ttyyppeesseett [--aaAAffFFggiiIIllnnrrttuuxx] [--pp] [_n_a_m_e[=_v_a_l_u_e] ...]
              Declare variables and/or give them attributes.  If no _n_a_m_es  are
              given then display the values of variables or functions.  The --pp
              option  will  display  the  attributes  and values of each _n_a_m_e.
              When --pp is used with _n_a_m_e arguments, additional  options,  other
              than --ff and --FF, are ignored.

              When --pp is supplied without _n_a_m_e arguments, ddeeccllaarree will display
              the attributes and values of all variables having the attributes
              specified  by  the  additional options.  If no other options are
              supplied with --pp, ddeeccllaarree will display the attributes and values
              of all shell variables.  The --ff option restricts the display  to
              shell functions.

              The --FF option inhibits the display of function definitions; only
              the  function  name and attributes are printed.  If the eexxttddeebbuugg
              shell option is enabled using sshhoopptt, the source  file  name  and
              line  number  where  each _n_a_m_e is defined are displayed as well.
              The --FF option implies --ff.

              The --gg option forces variables to be created or modified at  the
              global scope, even when ddeeccllaarree is executed in a shell function.
              It is ignored when ddeeccllaarree is not executed in a shell function.

              The  --II  option causes local variables to inherit the attributes
              (except the _n_a_m_e_r_e_f attribute) and value of any  existing  vari-
              able  with the same _n_a_m_e at a surrounding scope.  If there is no
              existing variable, the local variable is initially unset.

              The following options can be used to restrict  output  to  vari-
              ables  with the specified attribute or to give variables attrib-
              utes:
              --aa     Each _n_a_m_e  is  an  indexed  array  variable  (see  AArrrraayyss
                     above).
              --AA     Each  _n_a_m_e  is  an associative array variable (see AArrrraayyss
                     above).
              --ff     Each _n_a_m_e refers to a shell function.
              --ii     The variable is treated as an integer; arithmetic evalua-
                     tion (see AARRIITTHHMMEETTIICC EEVVAALLUUAATTIIOONN above) is performed  when
                     the variable is assigned a value.
              --ll     When  the  variable  is  assigned a value, all upper-case
                     characters are converted to lower-case.   The  upper-case
                     attribute is disabled.
              --nn     Give  each  _n_a_m_e  the _n_a_m_e_r_e_f attribute, making it a name
                     reference to another variable.  That  other  variable  is
                     defined  by  the  value of _n_a_m_e.  All references, assign-
                     ments, and attribute modifications to _n_a_m_e, except  those
                     using  or changing the --nn attribute itself, are performed
                     on the variable referenced by _n_a_m_e's value.  The  nameref
                     attribute cannot be applied to array variables.
              --rr     Make _n_a_m_es readonly.  These names cannot then be assigned
                     values by subsequent assignment statements or unset.
              --tt     Give each _n_a_m_e the _t_r_a_c_e attribute.  Traced functions in-
                     herit  the DDEEBBUUGG and RREETTUURRNN traps from the calling shell.
                     The trace attribute has no special meaning for variables.
              --uu     When the variable is assigned  a  value,  all  lower-case
                     characters  are  converted to upper-case.  The lower-case
                     attribute is disabled.
              --xx     Mark each _n_a_m_e for export to subsequent commands via  the
                     environment.

              Using  "+"  instead of "-" turns off the specified attribute in-
              stead, with the exceptions that ++aa and ++AA may not be used to de-
              stroy array variables and ++rr will not remove  the  readonly  at-
              tribute.

              When  used in a function, ddeeccllaarree and ttyyppeesseett make each _n_a_m_e lo-
              cal, as with the llooccaall command, unless the  --gg  option  is  sup-
              plied.   If  a variable name is followed by =_v_a_l_u_e, the value of
              the variable is set to _v_a_l_u_e.  When using --aa or --AA and the  com-
              pound  assignment  syntax  to create array variables, additional
              attributes do not take effect until subsequent assignments.

              The return value is 0 unless an invalid option  is  encountered,
              an  attempt  is made to define a function using "-f foo=bar", an
              attempt is made to assign a value to a readonly variable, an at-
              tempt is made to assign a value to an array variable without us-
              ing the compound assignment syntax (see AArrrraayyss  above),  one  of
              the _n_a_m_e_s is not a valid shell variable name, an attempt is made
              to  turn off readonly status for a readonly variable, an attempt
              is made to turn off array status for an array  variable,  or  an
              attempt is made to display a non-existent function with --ff.

       ddiirrss [[--ccllppvv]] [[++_n]] [[--_n]]
              Without options, display the list of currently remembered direc-
              tories.   The default display is on a single line with directory
              names separated by spaces.  Directories are added  to  the  list
              with  the  ppuusshhdd  command; the ppooppdd command removes entries from
              the list.  The current directory is always the  first  directory
              in the stack.

              Options, if supplied, have the following meanings:
              --cc     Clears  the  directory  stack  by deleting all of the en-
                     tries.
              --ll     Produces a listing  using  full  pathnames;  the  default
                     listing format uses a tilde to denote the home directory.
              --pp     Print the directory stack with one entry per line.
              --vv     Print  the  directory stack with one entry per line, pre-
                     fixing each entry with its index in the stack.
              ++_n     Displays the _nth entry counting from the left of the list
                     shown by ddiirrss when invoked without options, starting with
                     zero.
              --_n     Displays the _nth entry counting from  the  right  of  the
                     list shown by ddiirrss when invoked without options, starting
                     with zero.

              The  return value is 0 unless an invalid option is supplied or _n
              indexes beyond the end of the directory stack.

       ddiissoowwnn [--aarr] [--hh] [_i_d ...]
              Without options, remove each _i_d from the table of  active  jobs.
              Each  _i_d may be a job specification _j_o_b_s_p_e_c or a process ID _p_i_d;
              if _i_d is a _p_i_d, ddiissoowwnn uses the job containing _p_i_d as _j_o_b_s_p_e_c.

              If the --hh option is supplied, ddiissoowwnn does not  remove  the  jobs
              corresponding  to  each _i_d from the jobs table, but rather marks
              them so the shell does not send SSIIGGHHUUPP to the job if  the  shell
              receives a SSIIGGHHUUPP.

              If  no _i_d is supplied, the --aa option means to remove or mark all
              jobs; the --rr option without an _i_d argument removes or marks run-
              ning jobs.  If no _i_d is supplied, and neither the --aa nor the  --rr
              option is supplied, ddiissoowwnn removes or marks the current job.

              The return value is 0 unless an _i_d does not specify a valid job.

       eecchhoo [--nneeEE] [_a_r_g ...]
              Output  the  _a_r_gs,  separated  by spaces, followed by a newline.
              The return status is 0 unless a write error occurs.   If  --nn  is
              specified, the trailing newline is not printed.

              If  the  --ee option is given, eecchhoo interprets the following back-
              slash-escaped characters.  The --EE option disables interpretation
              of these escape characters, even on systems where they  are  in-
              terpreted  by  default.   The  xxppgg__eecchhoo  shell option determines
              whether or not eecchhoo interprets any options and expands these es-
              cape characters.  eecchhoo does not interpret ---- to mean the end  of
              options.

              eecchhoo interprets the following escape sequences:
              \\aa     alert (bell)
              \\bb     backspace
              \\cc     suppress further output
              \\ee
              \\EE     an escape character
              \\ff     form feed
              \\nn     new line
              \\rr     carriage return
              \\tt     horizontal tab
              \\vv     vertical tab
              \\\\     backslash
              \\00_n_n_n  The  eight-bit  character  whose value is the octal value
                     _n_n_n (zero to three octal digits).
              \\xx_H_H   The eight-bit character whose value  is  the  hexadecimal
                     value _H_H (one or two hex digits).
              \\uu_H_H_H_H The  Unicode (ISO/IEC 10646) character whose value is the
                     hexadecimal value _H_H_H_H (one to four hex digits).
              \\UU_H_H_H_H_H_H_H_H
                     The Unicode (ISO/IEC 10646) character whose value is  the
                     hexadecimal value _H_H_H_H_H_H_H_H (one to eight hex digits).

              eecchhoo  writes  any  unrecognized backslash-escaped characters un-
              changed.

       eennaabbllee [--aa] [--ddnnppss] [--ff _f_i_l_e_n_a_m_e] [_n_a_m_e ...]
              Enable and disable builtin shell commands.  Disabling a  builtin
              allows  an  executable  file  which has the same name as a shell
              builtin to be executed without specifying a full pathname,  even
              though the shell normally searches for builtins before files.

              If  --nn  is supplied, each _n_a_m_e is disabled; otherwise, _n_a_m_es are
              enabled.  For example, to use the tteesstt binary found  using  PPAATTHH
              instead of the shell builtin version, run "enable -n test".

              If  no  _n_a_m_e arguments are supplied, or if the --pp option is sup-
              plied, print a list of shell builtins.  With no other option ar-
              guments, the list consists of all enabled shell builtins.  If --nn
              is supplied, print only disabled builtins.  If --aa  is  supplied,
              the  list  printed  includes all builtins, with an indication of
              whether or not each is enabled.  The --ss option means to restrict
              the output to the POSIX _s_p_e_c_i_a_l builtins.

              The --ff option means to load the new builtin  command  _n_a_m_e  from
              shared object _f_i_l_e_n_a_m_e, on systems that support dynamic loading.
              If _f_i_l_e_n_a_m_e does not contain a slash, BBaasshh will use the value of
              the  BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH  variable  as a colon-separated list of
              directories in which to search for _f_i_l_e_n_a_m_e.   The  default  for
              BBAASSHH__LLOOAADDAABBLLEESS__PPAATTHH  is system-dependent, and may include "." to
              force a search of the current directory.   The  --dd  option  will
              delete  a builtin previously loaded with --ff.  If _-_s is used with
              _-_f, the new builtin becomes a POSIX special builtin.

              If no options are supplied and a _n_a_m_e is not  a  shell  builtin,
              eennaabbllee  will  attempt  to  load  _n_a_m_e from a shared object named
              _n_a_m_e, as if the command were "enable -f _n_a_m_e _n_a_m_e".

              The return value is 0 unless a _n_a_m_e is not a  shell  builtin  or
              there is an error loading a new builtin from a shared object.

       eevvaall [_a_r_g ...]
              Concatenate  the _a_r_gs together into a single command, separating
              them with spaces.  BBaasshh then reads and execute this command, and
              returns its exit status as the return status of eevvaall.  If  there
              are no _a_r_g_s, or only null arguments, eevvaall returns 0.

       eexxeecc [--ccll] [--aa _n_a_m_e] [_c_o_m_m_a_n_d [_a_r_g_u_m_e_n_t_s]]
              If  _c_o_m_m_a_n_d is specified, it replaces the shell without creating
              a new process.  _c_o_m_m_a_n_d cannot be a shell builtin  or  function.
              The _a_r_g_u_m_e_n_t_s become the arguments to _c_o_m_m_a_n_d.  If the --ll option
              is supplied, the shell places a dash at the beginning of the ze-
              roth  argument  passed  to _c_o_m_m_a_n_d.  This is what _l_o_g_i_n(1) does.
              The --cc option causes _c_o_m_m_a_n_d to be executed with an empty  envi-
              ronment.  If --aa is supplied, the shell passes _n_a_m_e as the zeroth
              argument to the executed command.

              If _c_o_m_m_a_n_d cannot be executed for some reason, a non-interactive
              shell  exits,  unless  the eexxeeccffaaiill shell option is enabled.  In
              that case, it returns a non-zero status.  An  interactive  shell
              returns  a  non-zero  status  if the file cannot be executed.  A
              subshell exits unconditionally if eexxeecc fails.

              If _c_o_m_m_a_n_d is not specified, any redirections take effect in the
              current shell, and the return status is 0.  If there is a  redi-
              rection error, the return status is 1.

       eexxiitt [_n]
              Cause  the  shell  to exit with a status of _n.  If _n is omitted,
              the exit status is that of the last command executed.  Any  trap
              on EEXXIITT is executed before the shell terminates.

       eexxppoorrtt [--ffnn] [_n_a_m_e[=_v_a_l_u_e]] ...
       eexxppoorrtt --pp [[--ff]]
              The  supplied _n_a_m_e_s are marked for automatic export to the envi-
              ronment of subsequently executed commands.  If the --ff option  is
              given, the _n_a_m_e_s refer to functions.

              The  --nn  option unexports, or removes the export attribute, from
              each _n_a_m_e.  If no _n_a_m_e_s are given, or if only the --pp  option  is
              supplied,  eexxppoorrtt displays a list of names of all exported vari-
              ables on the standard output.  Using --pp and --ff together displays
              exported functions.  The --pp option displays  output  in  a  form
              that may be reused as input.

              eexxppoorrtt  allows  the value of a variable to be set when it is ex-
              ported or unexported by following the variable name with =_v_a_l_u_e.
              This sets the value of the variable to _v_a_l_u_e while modifying the
              export attribute.  eexxppoorrtt returns an exit status of 0 unless  an
              invalid  option  is encountered, one of the _n_a_m_e_s is not a valid
              shell variable name, or --ff is supplied with a _n_a_m_e that is not a
              function.

       ffaallssee  Does nothing; returns a non-zero status.

       ffcc [--ee _e_n_a_m_e] [--llnnrr] [_f_i_r_s_t] [_l_a_s_t]
       ffcc --ss [_p_a_t=_r_e_p] [_c_m_d]
              The first form selects a range of commands from  _f_i_r_s_t  to  _l_a_s_t
              from  the  history  list  and  displays or edits and re-executes
              them.  _F_i_r_s_t and _l_a_s_t may be specified as a  string  (to  locate
              the  last command beginning with that string) or as a number (an
              index into the history list, where a negative number is used  as
              an offset from the current command number).

              When listing, a _f_i_r_s_t or _l_a_s_t of 0 is equivalent to -1 and -0 is
              equivalent to the current command (usually the ffcc command); oth-
              erwise  0 is equivalent to -1 and -0 is invalid.  If _l_a_s_t is not
              specified, it is set to the current command for listing (so that
              "fc -l -10" prints the last 10 commands) and to _f_i_r_s_t otherwise.
              If _f_i_r_s_t is not specified, it is set to the previous command for
              editing and -16 for listing.

              If the --ll option is supplied, the commands  are  listed  on  the
              standard  output.   The --nn option suppresses the command numbers
              when listing.  The --rr option reverses the order of the commands.

              Otherwise, ffcc invokes the editor named by _e_n_a_m_e on a  file  con-
              taining  those  commands.  If _e_n_a_m_e is not supplied, ffcc uses the
              value of the FFCCEEDDIITT variable, and the value of EEDDIITTOORR if  FFCCEEDDIITT
              is  not set.  If neither variable is set, ffcc uses _v_i_. When edit-
              ing is complete, ffcc reads the file containing  the  edited  com-
              mands and echoes and executes them.

              In  the second form, ffcc re-executes _c_o_m_m_a_n_d after replacing each
              instance of _p_a_t with _r_e_p.  _C_o_m_m_a_n_d is interpreted  the  same  as
              _f_i_r_s_t above.

              A  useful alias to use with ffcc is "r="fc -s"", so that typing "r
              cc" runs the last command beginning with "cc" and typing "r" re-
              executes the last command.

              If the first form is used, the return value is  zero  unless  an
              invalid  option  is encountered or _f_i_r_s_t or _l_a_s_t specify history
              lines out of range.  When editing and  re-executing  a  file  of
              commands, the return value is the value of the last command exe-
              cuted or failure if an error occurs with the temporary file.  If
              the second form is used, the return status is that of the re-ex-
              ecuted  command, unless _c_m_d does not specify a valid history en-
              try, in which case ffcc returns a non-zero status.

       ffgg [_j_o_b_s_p_e_c]
              Resume _j_o_b_s_p_e_c in the foreground, and make it the  current  job.
              If  _j_o_b_s_p_e_c  is  not  present, ffgg uses the shell's notion of the
              _c_u_r_r_e_n_t _j_o_b.  The return value is that  of  the  command  placed
              into  the foreground, or failure if run when job control is dis-
              abled or, when run with job control enabled, if _j_o_b_s_p_e_c does not
              specify a valid job or _j_o_b_s_p_e_c specifies a job that was  started
              without job control.

       ggeettooppttss _o_p_t_s_t_r_i_n_g _n_a_m_e [_a_r_g ...]
              ggeettooppttss  is  used  by shell scripts and functions to parse posi-
              tional parameters and obtain options and their arguments.   _o_p_t_-
              _s_t_r_i_n_g  contains  the  option  characters to be recognized; if a
              character is followed by a colon, the option is expected to have
              an argument, which should be separated from it by  white  space.
              The colon and question mark characters may not be used as option
              characters.

              Each  time  it is invoked, ggeettooppttss places the next option in the
              shell variable _n_a_m_e, initializing _n_a_m_e if it does not exist, and
              the index of the next argument to be processed into the variable
              OOPPTTIINNDD.  OOPPTTIINNDD is initialized to 1 each time  the  shell  or  a
              shell  script  is invoked.  When an option requires an argument,
              ggeettooppttss places that argument into the variable OOPPTTAARRGG.

              The shell does not reset OOPPTTIINNDD automatically; it must be  manu-
              ally  reset  between  multiple  calls to ggeettooppttss within the same
              shell invocation to use a new set of parameters.

              When it reaches the end of options, ggeettooppttss exits with a  return
              value  greater  than  zero.   OOPPTTIINNDD  is set to the index of the
              first non-option argument, and _n_a_m_e is set to ?.

              ggeettooppttss normally parses the positional parameters, but  if  more
              arguments  are  supplied as _a_r_g values, ggeettooppttss parses those in-
              stead.

              ggeettooppttss can report errors in two ways.  If the  first  character
              of  _o_p_t_s_t_r_i_n_g  is  a colon, ggeettooppttss uses _s_i_l_e_n_t error reporting.
              In normal operation, ggeettooppttss prints diagnostic messages when  it
              encounters  invalid options or missing option arguments.  If the
              variable OOPPTTEERRRR is set to 0, ggeettooppttss does not display any  error
              messages,  even  if  the  first  character of _o_p_t_s_t_r_i_n_g is not a
              colon.

              If ggeettooppttss detects an invalid option, it places ? into _n_a_m_e and,
              if not silent, prints an error message and  unsets  OOPPTTAARRGG.   If
              ggeettooppttss  is silent, it assigns the option character found to OOPP--
              TTAARRGG and does not print a diagnostic message.

              If a required argument is not found, and ggeettooppttss is not  silent,
              it sets the value of _n_a_m_e to a question mark (??), unsets OOPPTTAARRGG,
              and  prints a diagnostic message.  If ggeettooppttss is silent, it sets
              the value of _n_a_m_e to a colon (::) and sets OOPPTTAARRGG to  the  option
              character found.

              ggeettooppttss  returns true if an option, specified or unspecified, is
              found.  It returns false if the end of options is encountered or
              an error occurs.

       hhaasshh [--llrr] [--pp _f_i_l_e_n_a_m_e] [--ddtt] [_n_a_m_e]
              Each time hhaasshh is invoked, it remembers the full pathname of the
              command _n_a_m_e as  determined  by  searching  the  directories  in
              $$PPAATTHH.   Any previously-remembered pathname associated with _n_a_m_e
              is discarded.  If the --pp option is supplied, hhaasshh uses  _f_i_l_e_n_a_m_e
              as the full pathname of the command.

              The  --rr  option  causes the shell to forget all remembered loca-
              tions.  Assigning to the PPAATTHH variable also  clears  all  hashed
              filenames.   The --dd option causes the shell to forget the remem-
              bered location of each _n_a_m_e.

              If the --tt option is supplied, hhaasshh prints the full pathname cor-
              responding to each _n_a_m_e.  If multiple _n_a_m_e  arguments  are  sup-
              plied  with  --tt,  hhaasshh  prints the _n_a_m_e before the corresponding
              hashed full pathname.  The --ll option displays output in a format
              that may be reused as input.

              If no arguments are given, or  if  only  --ll  is  supplied,  hhaasshh
              prints  information  about remembered commands.  The --tt, --dd, and
              --pp options (the options that act on the _n_a_m_e arguments) are  mu-
              tually exclusive.  Only one will be active.  If more than one is
              supplied,  --tt  has higher priority than --pp, and both have higher
              priority than --dd.

              The return status is zero unless a _n_a_m_e is not found or  an  in-
              valid option is supplied.

       hheellpp [--ddmmss] [_p_a_t_t_e_r_n]
              Display  helpful information about builtin commands.  If _p_a_t_t_e_r_n
              is specified, hheellpp gives detailed help on all commands  matching
              _p_a_t_t_e_r_n  as described below; otherwise it displays a list of all
              the builtins and shell compound commands.

              Options, if supplied, have the follow meanings:

              --dd     Display a short description of each _p_a_t_t_e_r_n
              --mm     Display the description of each _p_a_t_t_e_r_n in a manpage-like
                     format
              --ss     Display only a short usage synopsis for each _p_a_t_t_e_r_n

              If _p_a_t_t_e_r_n contains pattern  matching  characters  (see  PPaatttteerrnn
              MMaattcchhiinngg  above) it's treated as a shell pattern and hheellpp prints
              the description of each help topic matching _p_a_t_t_e_r_n.

              If not, and _p_a_t_t_e_r_n exactly matches the name of  a  help  topic,
              hheellpp  prints the description associated with that topic.  Other-
              wise, hheellpp performs prefix matching and prints the  descriptions
              of all matching help topics.

              The return status is 0 unless no command matches _p_a_t_t_e_r_n.

       hhiissttoorryy [[_n]]
       hhiissttoorryy --cc
       hhiissttoorryy --dd _o_f_f_s_e_t
       hhiissttoorryy --dd _s_t_a_r_t-_e_n_d
       hhiissttoorryy --aannrrww [_f_i_l_e_n_a_m_e]
       hhiissttoorryy --pp _a_r_g [_a_r_g ...]
       hhiissttoorryy --ss _a_r_g [_a_r_g ...]
              With  no options, display the command history list with numbers.
              Entries prefixed with a ** have been modified.  An argument of  _n
              lists  only the last _n entries.  If the shell variable HHIISSTTTTIIMMEE--
              FFOORRMMAATT is set and not null, it is used as a  format  string  for
              _s_t_r_f_t_i_m_e(3)  to display the time stamp associated with each dis-
              played history entry.  If hhiissttoorryy uses HHIISSTTTTIIMMEEFFOORRMMAATT,  it  does
              not  print an intervening space between the formatted time stamp
              and the history entry.

              If _f_i_l_e_n_a_m_e is supplied, hhiissttoorryy uses it as the name of the his-
              tory file; if not, it uses the value of HHIISSTTFFIILLEE.   If  _f_i_l_e_n_a_m_e
              is  not  supplied and HHIISSTTFFIILLEE is unset or null, the --aa,, --nn,, --rr,,
              and --ww options have no effect.

              Options, if supplied, have the following meanings:
              --cc     Clear the history list by deleting all the entries.  This
                     can be used with the other options to replace the history
                     list.
              --dd _o_f_f_s_e_t
                     Delete the history entry at position _o_f_f_s_e_t.   If  _o_f_f_s_e_t
                     is negative, it is interpreted as relative to one greater
                     than the last history position, so negative indices count
                     back  from  the  end  of  the history, and an index of -1
                     refers to the current hhiissttoorryy --dd command.
              --dd _s_t_a_r_t-_e_n_d
                     Delete the range of  history  entries  between  positions
                     _s_t_a_r_t  and  _e_n_d, inclusive.  Positive and negative values
                     for _s_t_a_r_t and _e_n_d are interpreted as described above.
              --aa     Append the "new"  history  lines  to  the  history  file.
                     These  are  history  lines entered since the beginning of
                     the current bbaasshh session, but not already appended to the
                     history file.
              --nn     Read the history lines not already read from the  history
                     file and add them to the current history list.  These are
                     lines appended to the history file since the beginning of
                     the current bbaasshh session.
              --rr     Read the history file and append its contents to the cur-
                     rent history list.
              --ww     Write the current history list to the history file, over-
                     writing the history file.
              --pp     Perform  history  substitution  on the following _a_r_g_s and
                     display the result on the standard output, without  stor-
                     ing  the  results  in the history list.  Each _a_r_g must be
                     quoted to disable normal history expansion.
              --ss     Store the _a_r_g_s in the history list  as  a  single  entry.
                     The  last  command  in the history list is removed before
                     adding the _a_r_g_s.

              If the HHIISSTTTTIIMMEEFFOORRMMAATT variable is set, hhiissttoorryy writes  the  time
              stamp information associated with each history entry to the his-
              tory  file,  marked  with  the  history comment character as de-
              scribed above.  When the history file is read,  lines  beginning
              with  the  history  comment  character followed immediately by a
              digit are interpreted as timestamps for  the  following  history
              entry.

              The  return  value is 0 unless an invalid option is encountered,
              an error occurs while reading or writing the  history  file,  an
              invalid _o_f_f_s_e_t or range is supplied as an argument to --dd, or the
              history expansion supplied as an argument to --pp fails.

       jjoobbss [--llnnpprrss] [ _j_o_b_s_p_e_c ... ]
       jjoobbss --xx _c_o_m_m_a_n_d [ _a_r_g_s ... ]
              The first form lists the active jobs.  The options have the fol-
              lowing meanings:
              --ll     List process IDs in addition to the normal information.
              --nn     Display  information  only  about  jobs that have changed
                     status since the user was last notified of their status.
              --pp     List only the process  ID  of  the  job's  process  group
                     leader.
              --rr     Display only running jobs.
              --ss     Display only stopped jobs.

              If  _j_o_b_s_p_e_c  is  supplied,  jjoobbss restricts output to information
              about that job.  The return status is 0 unless an invalid option
              is encountered or an invalid _j_o_b_s_p_e_c is supplied.

              If the --xx option is supplied, jjoobbss replaces any _j_o_b_s_p_e_c found in
              _c_o_m_m_a_n_d or _a_r_g_s with the corresponding process group ID, and ex-
              ecutes _c_o_m_m_a_n_d, passing it _a_r_g_s, returning its exit status.

       kkiillll [--ss _s_i_g_s_p_e_c | --nn _s_i_g_n_u_m | --_s_i_g_s_p_e_c] _i_d [ ... ]
       kkiillll --ll|--LL [_s_i_g_s_p_e_c | _e_x_i_t___s_t_a_t_u_s]
              Send the signal specified by _s_i_g_s_p_e_c or _s_i_g_n_u_m to the  processes
              named by each _i_d.  Each _i_d may be a job specification _j_o_b_s_p_e_c or
              a  process  ID _p_i_d.  _s_i_g_s_p_e_c is either a case-insensitive signal
              name such as SSIIGGKKIILLLL (with or without the SSIIGG prefix) or a  sig-
              nal  number;  _s_i_g_n_u_m is a signal number.  If _s_i_g_s_p_e_c is not sup-
              plied, then kkiillll sends SSIIGGTTEERRMM.

              The --ll option lists the signal names.  If any arguments are sup-
              plied when --ll is given, kkiillll lists the names of the signals cor-
              responding to the arguments, and the return status  is  0.   The
              _e_x_i_t___s_t_a_t_u_s  argument to --ll is a number specifying either a sig-
              nal number or the exit status of a process terminated by a  sig-
              nal;  if it is supplied, kkiillll prints the name of the signal that
              caused the process to terminate.  kkiillll assumes that process exit
              statuses are greater than 128; anything less than that is a sig-
              nal number.  The --LL option is equivalent to --ll.

              kkiillll returns true if at least one signal was successfully  sent,
              or false if an error occurs or an invalid option is encountered.

       lleett _a_r_g [_a_r_g ...]
              Each  _a_r_g  is  evaluated as an arithmetic expression (see AARRIITTHH--
              MMEETTIICC EEVVAALLUUAATTIIOONN above).  If the last _a_r_g evaluates  to  0,  lleett
              returns 1; otherwise lleett returns 0.

       llooccaall [_o_p_t_i_o_n] [_n_a_m_e[=_v_a_l_u_e] ... | - ]
              For each argument, create a local variable named _n_a_m_e and assign
              it  _v_a_l_u_e.  The _o_p_t_i_o_n can be any of the options accepted by ddee--
              ccllaarree.  When llooccaall is used within  a  function,  it  causes  the
              variable  _n_a_m_e  to have a visible scope restricted to that func-
              tion and its children.  It is an error to  use  llooccaall  when  not
              within a function.

              If  _n_a_m_e  is  -,  it makes the set of shell options local to the
              function in which llooccaall is invoked: any  shell  options  changed
              using  the sseett builtin inside the function after the call to lloo--
              ccaall are restored to their original values when the function  re-
              turns.   The restore is performed as if a series of sseett commands
              were executed to restore the values that were  in  place  before
              the function.

              With  no operands, llooccaall writes a list of local variables to the
              standard output.

              The return status is 0 unless llooccaall is used outside a  function,
              an invalid _n_a_m_e is supplied, or _n_a_m_e is a readonly variable.

       llooggoouutt [[_n]]
              Exit  a login shell, returning a status of _n to the shell's par-
              ent.

       mmaappffiillee [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
       _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
       rreeaaddaarrrraayy [--dd _d_e_l_i_m] [--nn _c_o_u_n_t] [--OO _o_r_i_g_i_n] [--ss _c_o_u_n_t] [--tt] [--uu _f_d] [--CC
       _c_a_l_l_b_a_c_k] [--cc _q_u_a_n_t_u_m] [_a_r_r_a_y]
              Read lines from the standard input, or from file  descriptor  _f_d
              if  the  --uu  option is supplied, into the indexed array variable
              _a_r_r_a_y.  The variable MMAAPPFFIILLEE is the default _a_r_r_a_y.  Options,  if
              supplied, have the following meanings:
              --dd     Use  the first character of _d_e_l_i_m to terminate each input
                     line, rather than newline.  If _d_e_l_i_m is the empty string,
                     mmaappffiillee will terminate a line when it reads a NUL charac-
                     ter.
              --nn     Copy at most _c_o_u_n_t lines.  If _c_o_u_n_t is 0, copy all lines.
              --OO     Begin assigning to _a_r_r_a_y at index  _o_r_i_g_i_n.   The  default
                     index is 0.
              --ss     Discard the first _c_o_u_n_t lines read.
              --tt     Remove  a trailing _d_e_l_i_m (default newline) from each line
                     read.
              --uu     Read lines from file descriptor _f_d instead of  the  stan-
                     dard input.
              --CC     Evaluate  _c_a_l_l_b_a_c_k each time _q_u_a_n_t_u_m lines are read.  The
                     --cc option specifies _q_u_a_n_t_u_m.
              --cc     Specify the number of lines read  between  each  call  to
                     _c_a_l_l_b_a_c_k.

              If  --CC  is  specified  without  --cc, the default quantum is 5000.
              When _c_a_l_l_b_a_c_k is evaluated, it is supplied the index of the next
              array element to be assigned and the line to be assigned to that
              element as additional arguments.  _c_a_l_l_b_a_c_k  is  evaluated  after
              the line is read but before the array element is assigned.

              If  not supplied with an explicit origin, mmaappffiillee will clear _a_r_-
              _r_a_y before assigning to it.

              mmaappffiillee returns zero unless an invalid option or option argument
              is supplied, _a_r_r_a_y is invalid or unassignable, or  if  _a_r_r_a_y  is
              not an indexed array.

       ppooppdd [-nn] [+_n] [-_n]
              Remove  entries from the directory stack.  The elements are num-
              bered from 0 starting at the first directory listed by ddiirrss,  so
              ppooppdd  is  equivalent  to "popd +0."  With no arguments, ppooppdd re-
              moves the top directory from the stack, and changes to  the  new
              top directory.  Arguments, if supplied, have the following mean-
              ings:
              --nn     Suppress the normal change of directory when removing di-
                     rectories from the stack, only manipulate the stack.
              ++_n     Remove  the  _nth entry counting from the left of the list
                     shown by ddiirrss, starting with zero, from the  stack.   For
                     example: "popd +0" removes the first directory, "popd +1"
                     the second.
              --_n     Remove  the _nth entry counting from the right of the list
                     shown by ddiirrss, starting with zero.   For  example:  "popd
                     -0"  removes  the  last  directory, "popd -1" the next to
                     last.

              If the top element of the directory stack is modified,  and  the
              _-_n  option  was not supplied, ppooppdd uses the ccdd builtin to change
              to the directory at the top of the stack.  If the ccdd fails, ppooppdd
              returns a non-zero value.

              Otherwise, ppooppdd returns false if an invalid option is  supplied,
              the  directory stack is empty, or _n specifies a non-existent di-
              rectory stack entry.

              If the ppooppdd command is successful, bbaasshh runs ddiirrss  to  show  the
              final  contents of the directory stack, and the return status is
              0.

       pprriinnttff [--vv _v_a_r] _f_o_r_m_a_t [_a_r_g_u_m_e_n_t_s]
              Write the formatted _a_r_g_u_m_e_n_t_s to the standard output  under  the
              control  of the _f_o_r_m_a_t.  The --vv option assigns the output to the
              variable _v_a_r rather than printing it to the standard output.

              The _f_o_r_m_a_t is a character string which contains three  types  of
              objects:  plain  characters, which are simply copied to standard
              output, character escape  sequences,  which  are  converted  and
              copied  to  the standard output, and format specifications, each
              of which causes printing of the next  successive  _a_r_g_u_m_e_n_t.   In
              addition  to  the  standard  _p_r_i_n_t_f(3)  format  characters ccCCssSS--
              nnddiioouuxxXXeeEEffFFggGGaaAA, pprriinnttff interprets the following additional for-
              mat specifiers:
              %%bb     causes pprriinnttff to expand backslash escape sequences in the
                     corresponding _a_r_g_u_m_e_n_t in the same way as eecchhoo --ee.
              %%qq     causes pprriinnttff to output the corresponding _a_r_g_u_m_e_n_t  in  a
                     format  that can be reused as shell input.  %%qq and %%QQ use
                     the $$'''' quoting style if any characters in  the  argument
                     string  require  it, and backslash quoting otherwise.  If
                     the format string uses the _p_r_i_n_t_f alternate  form,  these
                     two  formats  quote  the  argument  string  using  single
                     quotes.
              %%QQ     like %%qq, but applies any supplied precision to the  _a_r_g_u_-
                     _m_e_n_t before quoting it.
              %%((_d_a_t_e_f_m_t))TT
                     causes  pprriinnttff  to  output the date-time string resulting
                     from using _d_a_t_e_f_m_t as a format  string  for  _s_t_r_f_t_i_m_e(3).
                     The corresponding _a_r_g_u_m_e_n_t is an integer representing the
                     number of seconds since the epoch.  This format specifier
                     recognizes two special argument values: -1 represents the
                     current  time,  and  -2 represents the time the shell was
                     invoked.  If no argument is specified, conversion behaves
                     as if -1 had been supplied.  This is an exception to  the
                     usual pprriinnttff behavior.

              The %b, %q, and %T format specifiers all use the field width and
              precision arguments from the format specification and write that
              many  bytes from (or use that wide a field for) the expanded ar-
              gument, which usually contains more characters than  the  origi-
              nal.

              The %n format specifier accepts a corresponding argument that is
              treated as a shell variable name.

              The  %s  and  %c  format specifiers accept an l (long) modifier,
              which forces them to convert the argument string to a wide-char-
              acter string and apply any supplied field width and precision in
              terms of characters, not bytes.  The %S and %C format specifiers
              are equivalent to %ls and %lc, respectively.

              Arguments to non-string format specifiers are treated as C  con-
              stants, except that a leading plus or minus sign is allowed, and
              if  the leading character is a single or double quote, the value
              is the numeric value of the following character, using the  cur-
              rent locale.

              The  _f_o_r_m_a_t  is  reused as necessary to consume all of the _a_r_g_u_-
              _m_e_n_t_s.  If the _f_o_r_m_a_t requires more _a_r_g_u_m_e_n_t_s than are supplied,
              the extra format specifications behave as if  a  zero  value  or
              null  string,  as  appropriate,  had  been supplied.  The return
              value is zero on success, non-zero if an invalid option is  sup-
              plied or a write or assignment error occurs.

       ppuusshhdd [--nn] [+_n] [-_n]
       ppuusshhdd [--nn] [_d_i_r]
              Add a directory to the top of the directory stack, or rotate the
              stack,  making  the new top of the stack the current working di-
              rectory.  With no arguments, ppuusshhdd exchanges the  top  two  ele-
              ments  of the directory stack.  Arguments, if supplied, have the
              following meanings:
              --nn     Suppress the normal change of directory when rotating  or
                     adding  directories  to  the  stack,  only manipulate the
                     stack.
              ++_n     Rotate the stack so that the _nth directory (counting from
                     the left of the list shown by ddiirrss, starting  with  zero)
                     is at the top.
              --_n     Rotates  the  stack  so  that the _nth directory (counting
                     from the right of the list shown by ddiirrss,  starting  with
                     zero) is at the top.
              _d_i_r    Adds _d_i_r to the directory stack at the top.

              After the stack has been modified, if the --nn option was not sup-
              plied,  ppuusshhdd  uses the ccdd builtin to change to the directory at
              the top of the stack.  If the ccdd fails, ppuusshhdd returns a non-zero
              value.

              Otherwise, if no arguments are supplied, ppuusshhdd returns zero  un-
              less  the directory stack is empty.  When rotating the directory
              stack, ppuusshhdd returns zero unless the directory stack is empty or
              _n specifies a non-existent directory stack element.

              If the ppuusshhdd command is successful, bbaasshh runs ddiirrss to  show  the
              final contents of the directory stack.

       ppwwdd [--LLPP]
              Print  the  absolute  pathname of the current working directory.
              The pathname printed contains no symbolic links if the --PP option
              is supplied or the --oo pphhyyssiiccaall option to the sseett builtin command
              is enabled.  If the --LL option is used, the pathname printed  may
              contain  symbolic links.  The return status is 0 unless an error
              occurs while reading the name of the current directory or an in-
              valid option is supplied.

       rreeaadd [--EEeerrss] [--aa _a_n_a_m_e] [--dd _d_e_l_i_m] [--ii _t_e_x_t] [--nn _n_c_h_a_r_s] [--NN _n_c_h_a_r_s]
       [--pp _p_r_o_m_p_t] [--tt _t_i_m_e_o_u_t] [--uu _f_d] [_n_a_m_e ...]
              Read one line from the standard input, or from the file descrip-
              tor _f_d supplied as an argument to the --uu option, split  it  into
              words  as  described  above under WWoorrdd SSpplliittttiinngg, and assign the
              first word to the first _n_a_m_e, the  second  word  to  the  second
              _n_a_m_e,  and  so  on.  If there are more words than names, the re-
              maining words and their intervening delimiters are  assigned  to
              the  last  _n_a_m_e.   If  there are fewer words read from the input
              stream than names, the remaining names are assigned  empty  val-
              ues.   The  characters in the value of the IIFFSS variable are used
              to split the line into words using the same rules the shell uses
              for expansion (described above under WWoorrdd SSpplliittttiinngg).  The back-
              slash character (\\) removes any special  meaning  for  the  next
              character read and is used for line continuation.

              Options, if supplied, have the following meanings:
              --aa _a_n_a_m_e
                     The words are assigned to sequential indices of the array
                     variable _a_n_a_m_e, starting at 0.  _a_n_a_m_e is unset before any
                     new  values  are  assigned.  Other _n_a_m_e arguments are ig-
                     nored.
              --dd _d_e_l_i_m
                     The first character of _d_e_l_i_m terminates the  input  line,
                     rather  than newline.  If _d_e_l_i_m is the empty string, rreeaadd
                     will terminate a line when it reads a NUL character.
              --ee     If the standard input is coming  from  a  terminal,  rreeaadd
                     uses  rreeaaddlliinnee  (see  RREEAADDLLIINNEE above) to obtain the line.
                     RReeaaddlliinnee uses the current (or default,  if  line  editing
                     was  not  previously  active)  editing settings, but uses
                     rreeaaddlliinnee's default filename completion.
              --EE     If the standard input is coming  from  a  terminal,  rreeaadd
                     uses  rreeaaddlliinnee  (see  RREEAADDLLIINNEE above) to obtain the line.
                     RReeaaddlliinnee uses the current (or default,  if  line  editing
                     was  not  previously  active)  editing settings, but uses
                     bash's default completion, including programmable comple-
                     tion.
              --ii _t_e_x_t
                     If rreeaaddlliinnee is being used to read the line,  rreeaadd  places
                     _t_e_x_t into the editing buffer before editing begins.
              --nn _n_c_h_a_r_s
                     rreeaadd  returns after reading _n_c_h_a_r_s characters rather than
                     waiting for a complete line of input, unless  it  encoun-
                     ters  EOF or rreeaadd times out, but honors a delimiter if it
                     reads fewer than _n_c_h_a_r_s characters before the delimiter.
              --NN _n_c_h_a_r_s
                     rreeaadd returns  after  reading  exactly  _n_c_h_a_r_s  characters
                     rather  than waiting for a complete line of input, unless
                     it encounters EOF or rreeaadd times out.  Any delimiter char-
                     acters in the input are not treated specially and do  not
                     cause rreeaadd to return until it has read _n_c_h_a_r_s characters.
                     The result is not split on the characters in IIFFSS; the in-
                     tent is that the variable is assigned exactly the charac-
                     ters  read  (with  the exception of backslash; see the --rr
                     option below).
              --pp _p_r_o_m_p_t
                     Display _p_r_o_m_p_t on standard error, without a trailing new-
                     line, before attempting to read any input,  but  only  if
                     input is coming from a terminal.
              --rr     Backslash does not act as an escape character.  The back-
                     slash  is considered to be part of the line.  In particu-
                     lar, a backslash-newline pair may not then be used  as  a
                     line continuation.
              --ss     Silent mode.  If input is coming from a terminal, charac-
                     ters are not echoed.
              --tt _t_i_m_e_o_u_t
                     Cause  rreeaadd to time out and return failure if it does not
                     read a complete line of input (or a specified  number  of
                     characters)  within  _t_i_m_e_o_u_t  seconds.   _t_i_m_e_o_u_t may be a
                     decimal number with a fractional  portion  following  the
                     decimal  point.  This option is only effective if rreeaadd is
                     reading input from a terminal,  pipe,  or  other  special
                     file;  it  has no effect when reading from regular files.
                     If rreeaadd times out, it saves any partial input  read  into
                     the  specified  variable  _n_a_m_e,  and  the  exit status is
                     greater than 128.  If _t_i_m_e_o_u_t is 0, rreeaadd returns  immedi-
                     ately,  without  trying  to read any data.  In this case,
                     the exit status is 0 if input is available on the  speci-
                     fied  file  descriptor, or the read will return EOF, non-
                     zero otherwise.
              --uu _f_d  Read input from file descriptor _f_d instead of  the  stan-
                     dard input.

              Other  than  the  case where _d_e_l_i_m is the empty string, rreeaadd ig-
              nores any NUL characters in the input.

              If no _n_a_m_e_s are supplied, rreeaadd assigns the  line  read,  without
              the  ending  delimiter but otherwise unmodified, to the variable
              RREEPPLLYY.

              The exit status is zero, unless end-of-file is encountered, rreeaadd
              times out (in which case the status  is  greater  than  128),  a
              variable assignment error (such as assigning to a readonly vari-
              able)  occurs,  or an invalid file descriptor is supplied as the
              argument to --uu.

       rreeaaddoonnllyy [--aaAAff] [--pp] [_n_a_m_e[=_w_o_r_d] ...]
              The given _n_a_m_e_s are marked readonly; the values of  these  _n_a_m_e_s
              may not be changed by subsequent assignment or unset.  If the --ff
              option  is  supplied, each _n_a_m_e refers to a shell function.  The
              --aa option restricts the variables to indexed arrays; the --AA  op-
              tion restricts the variables to associative arrays.  If both op-
              tions  are  supplied, --AA takes precedence.  If no _n_a_m_e arguments
              are supplied, or if the --pp option is supplied, print a  list  of
              all  readonly  names.  The other options may be used to restrict
              the output to a subset of the set of readonly names.  The --pp op-
              tion displays output in a format that may be reused as input.

              rreeaaddoonnllyy allows the value of a variable to be set  at  the  same
              time the readonly attribute is changed by following the variable
              name  with  =_v_a_l_u_e.   This  sets the value of the variable is to
              _v_a_l_u_e while modifying the readonly attribute.

              The return status is 0 unless an invalid option is  encountered,
              one  of  the  _n_a_m_e_s is not a valid shell variable name, or --ff is
              supplied with a _n_a_m_e that is not a function.

       rreettuurrnn [_n]
              Stop executing a shell function or sourced file and  return  the
              value specified by _n to its caller.  If _n is omitted, the return
              status  is that of the last command executed.  If rreettuurrnn is exe-
              cuted by a trap handler, the last command used to determine  the
              status is the last command executed before the trap handler.  If
              rreettuurrnn is executed during a DDEEBBUUGG trap, the last command used to
              determine  the  status  is the last command executed by the trap
              handler before rreettuurrnn was invoked.

              When rreettuurrnn is used to terminate execution of a script being ex-
              ecuted by the ..  (ssoouurrccee) command, it causes the shell  to  stop
              executing  that script and return either _n or the exit status of
              the last command executed within the script as the  exit  status
              of  the script.  If _n is supplied, the return value is its least
              significant 8 bits.

              Any command associated with the RREETTUURRNN trap is  executed  before
              execution resumes after the function or script.

              The  return  status  is non-zero if rreettuurrnn is supplied a non-nu-
              meric argument, or is used outside a function and not during ex-
              ecution of a script by .. or ssoouurrccee.

       sseett [--aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [--oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...]
       sseett [++aabbeeffhhkkmmnnppttuuvvxxBBCCEEHHPPTT] [++oo _o_p_t_i_o_n_-_n_a_m_e] [----] [--] [_a_r_g ...]
       sseett --oo
       sseett ++oo Without options, display the name and value of each shell  vari-
              able  in a format that can be reused as input for setting or re-
              setting the currently-set variables.  Read-only variables cannot
              be reset.  In posix mode, only shell variables are listed.   The
              output  is sorted according to the current locale.  When options
              are specified, they set or unset shell  attributes.   Any  argu-
              ments  remaining  after  option processing are treated as values
              for the positional parameters and are assigned, in order, to $$11,
              $$22, ..., $$_n.  Options, if specified, have  the  following  mean-
              ings:
              --aa      Each variable or function that is created or modified is
                      given  the export attribute and marked for export to the
                      environment of subsequent commands.
              --bb      Report the status of terminated background jobs  immedi-
                      ately, rather than before the next primary prompt or af-
                      ter  a foreground command terminates.  This is effective
                      only when job control is enabled.
              --ee      Exit immediately if a _p_i_p_e_l_i_n_e (which may consist  of  a
                      single  _s_i_m_p_l_e  _c_o_m_m_a_n_d),  a _l_i_s_t, or a _c_o_m_p_o_u_n_d _c_o_m_m_a_n_d
                      (see SSHHEELLLL GGRRAAMMMMAARR above), exits with a non-zero status.
                      The shell does not exit if the  command  that  fails  is
                      part  of  the command list immediately following a wwhhiillee
                      or uunnttiill reserved word, part of the test  following  the
                      iiff  or eelliiff reserved words, part of any command executed
                      in a &&&& or |||| list except the command following the  fi-
                      nal  &&&&  or  ||||,  any command in a pipeline but the last
                      (subject to the state of the ppiippeeffaaiill shell option),  or
                      if  the command's return value is being inverted with !!.
                      If a compound command other than a  subshell  returns  a
                      non-zero  status  because  a command failed while --ee was
                      being ignored, the shell does not exit.  A trap on  EERRRR,
                      if set, is executed before the shell exits.  This option
                      applies to the shell environment and each subshell envi-
                      ronment  separately  (see  CCOOMMMMAANNDD EEXXEECCUUTTIIOONN EENNVVIIRROONNMMEENNTT
                      above), and may cause subshells to exit before executing
                      all the commands in the subshell.

                      If a compound command or shell function  executes  in  a
                      context  where --ee is being ignored, none of the commands
                      executed within the compound command  or  function  body
                      will  be  affected  by the --ee setting, even if --ee is set
                      and a command returns a failure status.  If  a  compound
                      command  or  shell function sets --ee while executing in a
                      context where --ee is ignored, that setting will not  have
                      any  effect  until  the  compound command or the command
                      containing the function call completes.
              --ff      Disable pathname expansion.
              --hh      Remember the location of commands as they are looked  up
                      for execution.  This is enabled by default.
              --kk      All  arguments  in the form of assignment statements are
                      placed in the environment for a command, not just  those
                      that precede the command name.
              --mm      Monitor  mode.   Job control is enabled.  This option is
                      on by default for interactive  shells  on  systems  that
                      support  it  (see JJOOBB CCOONNTTRROOLL above).  All processes run
                      in a separate process group.  When a background job com-
                      pletes, the shell prints a line containing its exit sta-
                      tus.
              --nn      Read commands but do not execute them.  This may be used
                      to check a shell script for syntax errors.  This is  ig-
                      nored by interactive shells.
              --oo _o_p_t_i_o_n_-_n_a_m_e
                      The _o_p_t_i_o_n_-_n_a_m_e can be one of the following:
                      aalllleexxppoorrtt
                              Same as --aa.
                      bbrraacceeeexxppaanndd
                              Same as --BB.
                      eemmaaccss   Use  an  emacs-style command line editing inter-
                              face.  This is enabled by default when the shell
                              is interactive, unless the shell is started with
                              the ----nnooeeddiittiinngg option.  This also  affects  the
                              editing interface used for rreeaadd --ee.
                      eerrrreexxiitt Same as --ee.
                      eerrrrttrraaccee
                              Same as --EE.
                      ffuunnccttrraaccee
                              Same as --TT.
                      hhaasshhaallll Same as --hh.
                      hhiisstteexxppaanndd
                              Same as --HH.
                      hhiissttoorryy Enable command history, as described above under
                              HHIISSTTOORRYY.  This option is on by default in inter-
                              active shells.
                      iiggnnoorreeeeooff
                              The   effect   is   as   if  the  shell  command
                              "IGNOREEOF=10"  had  been  executed  (see  SShheellll
                              VVaarriiaabblleess above).
                      kkeeyywwoorrdd Same as --kk.
                      mmoonniittoorr Same as --mm.
                      nnoocclloobbbbeerr
                              Same as --CC.
                      nnooeexxeecc  Same as --nn.
                      nnoogglloobb  Same as --ff.
                      nnoolloogg   Currently ignored.
                      nnoottiiffyy  Same as --bb.
                      nnoouunnsseett Same as --uu.
                      oonneeccmmdd  Same as --tt.
                      pphhyyssiiccaall
                              Same as --PP.
                      ppiippeeffaaiill
                              If  set,  the  return value of a pipeline is the
                              value of the last (rightmost)  command  to  exit
                              with  a non-zero status, or zero if all commands
                              in the pipeline exit successfully.  This  option
                              is disabled by default.
                      ppoossiixx   Enable  posix  mode; change the behavior of bbaasshh
                              where the default  operation  differs  from  the
                              POSIX  standard  to match the standard.  See SSEEEE
                              AALLSSOO below for a reference to  a  document  that
                              details how posix mode affects bash's behavior.
                      pprriivviilleeggeedd
                              Same as --pp.
                      vveerrbboossee Same as --vv.
                      vvii      Use  a  vi-style command line editing interface.
                              This also affects the editing interface used for
                              rreeaadd --ee.
                      xxttrraaccee  Same as --xx.
                      If --oo is supplied with no _o_p_t_i_o_n_-_n_a_m_e,  sseett  prints  the
                      current  shell  option settings.  If ++oo is supplied with
                      no _o_p_t_i_o_n_-_n_a_m_e, sseett prints a series of sseett  commands  to
                      recreate  the  current  option  settings on the standard
                      output.
              --pp      Turn on _p_r_i_v_i_l_e_g_e_d mode.  In this mode, the  shell  does
                      not  read  the $$EENNVV and $$BBAASSHH__EENNVV files, shell functions
                      are not inherited from the environment,  and  the  SSHHEELL--
                      LLOOPPTTSS,  BBAASSHHOOPPTTSS,  CCDDPPAATTHH,  and GGLLOOBBIIGGNNOORREE variables, if
                      they appear in the environment,  are  ignored.   If  the
                      shell  is started with the effective user (group) id not
                      equal to the real user (group) id, and the --pp option  is
                      not  supplied, these actions are taken and the effective
                      user id is set to the real user id.  If the --pp option is
                      supplied at startup, the effective user id is not reset.
                      Turning this option off causes the  effective  user  and
                      group ids to be set to the real user and group ids.
              --rr      Enable restricted shell mode.  This option cannot be un-
                      set once it has been set.
              --tt      Exit after reading and executing one command.
              --uu      Treat unset variables and parameters other than the spe-
                      cial  parameters  "@"  and  "*", or array variables sub-
                      scripted with "@" or "*", as an  error  when  performing
                      parameter  expansion.   If  expansion is attempted on an
                      unset variable or parameter, the shell prints  an  error
                      message,  and, if not interactive, exits with a non-zero
                      status.
              --vv      Print shell input lines as they are read.
              --xx      After expanding each _s_i_m_p_l_e _c_o_m_m_a_n_d, ffoorr  command,  ccaassee
                      command, sseelleecctt command, or arithmetic ffoorr command, dis-
                      play  the expanded value of PPSS44, followed by the command
                      and its expanded arguments or associated word  list,  to
                      the standard error.
              --BB      The  shell performs brace expansion (see BBrraaccee EExxppaannssiioonn
                      above).  This is on by default.
              --CC      If set, bbaasshh does not overwrite an  existing  file  with
                      the  >>,  >>&&,  and  <<>>  redirection operators.  Using the
                      redirection operator >>|| instead of >> will override  this
                      and force the creation of an output file.
              --EE      If set, any trap on EERRRR is inherited by shell functions,
                      command  substitutions,  and commands executed in a sub-
                      shell environment.  The EERRRR trap is normally not  inher-
                      ited in such cases.
              --HH      Enable !!  style history substitution.  This option is on
                      by default when the shell is interactive.
              --PP      If  set,  the shell does not resolve symbolic links when
                      executing commands such as ccdd that  change  the  current
                      working  directory.   It  uses  the  physical  directory
                      structure instead.  By default, bbaasshh follows the logical
                      chain of  directories  when  performing  commands  which
                      change the current directory.
              --TT      If  set,  any traps on DDEEBBUUGG and RREETTUURRNN are inherited by
                      shell functions, command substitutions, and commands ex-
                      ecuted in a subshell environment.  The DDEEBBUUGG and  RREETTUURRNN
                      traps are normally not inherited in such cases.
              ----      If no arguments follow this option, unset the positional
                      parameters.  Otherwise, set the positional parameters to
                      the _a_r_gs, even if some of them begin with a --.
              --       Signal the end of options, and assign all remaining _a_r_gs
                      to the positional parameters.  The --xx and --vv options are
                      turned  off.  If there are no _a_r_gs, the positional para-
                      meters remain unchanged.

              The options are off by default unless otherwise noted.  Using  +
              rather  than  -  causes these options to be turned off.  The op-
              tions can also be specified as arguments to an invocation of the
              shell.  The current set of options may be found in $$--.  The  re-
              turn  status  is always zero unless an invalid option is encoun-
              tered.

       sshhiifftt [_n]
              Rename positional parameters from _n+1 ... to $$11 ........  Parameters
              represented by the numbers $$## down to $$##-_n+1 are unset.  _n  must
              be  a  non-negative number less than or equal to $$##.  If _n is 0,
              no parameters are changed.  If _n is not given, it is assumed  to
              be  1.   If  _n is greater than $$##, the positional parameters are
              not changed.  The return status is greater than  zero  if  _n  is
              greater than $$## or less than zero; otherwise 0.

       sshhoopptt [--ppqqssuu] [--oo] [_o_p_t_n_a_m_e ...]
              Toggle  the values of settings controlling optional shell behav-
              ior.  The settings can be either those listed below, or, if  the
              --oo option is used, those available with the --oo option to the sseett
              builtin command.

              With  no  options,  or with the --pp option, display a list of all
              settable options, with an indication of whether or not  each  is
              set;  if  any _o_p_t_n_a_m_e_s are supplied, the output is restricted to
              those options.  The --pp option displays output in a form that may
              be reused as input.

              Other options have the following meanings:
              --ss     Enable (set) each _o_p_t_n_a_m_e.
              --uu     Disable (unset) each _o_p_t_n_a_m_e.
              --qq     Suppresses normal output (quiet mode); the return  status
                     indicates whether the _o_p_t_n_a_m_e is set or unset.  If multi-
                     ple  _o_p_t_n_a_m_e  arguments  are supplied with --qq, the return
                     status is zero if all _o_p_t_n_a_m_e_s are enabled; non-zero oth-
                     erwise.
              --oo     Restricts the values of _o_p_t_n_a_m_e to be those  defined  for
                     the --oo option to the sseett builtin.

              If  either  --ss  or  --uu  is used with no _o_p_t_n_a_m_e arguments, sshhoopptt
              shows only those options which are set or  unset,  respectively.
              Unless  otherwise  noted, the sshhoopptt options are disabled (unset)
              by default.

              The return status when listing options is zero if  all  _o_p_t_n_a_m_e_s
              are  enabled, non-zero otherwise.  When setting or unsetting op-
              tions, the return status is zero unless  an  _o_p_t_n_a_m_e  is  not  a
              valid shell option.

              The list of sshhoopptt options is:

              aarrrraayy__eexxppaanndd__oonnccee
                      If  set, the shell suppresses multiple evaluation of as-
                      sociative and indexed array subscripts during arithmetic
                      expression evaluation, while executing builtins that can
                      perform  variable  assignments,  and   while   executing
                      builtins that perform array dereferencing.
              aassssoocc__eexxppaanndd__oonnccee
                      Deprecated; a synonym for aarrrraayy__eexxppaanndd__oonnccee.
              aauuttooccdd  If  set,  a command name that is the name of a directory
                      is executed as if it were the argument to  the  ccdd  com-
                      mand.  This option is only used by interactive shells.
              bbaasshh__ssoouurrccee__ffuullllppaatthh
                      If  set,  filenames added to the BBAASSHH__SSOOUURRCCEE array vari-
                      able are converted to full pathnames  (see  SShheellll  VVaarrii--
                      aabblleess above).
              ccddaabbllee__vvaarrss
                      If  set,  an  argument to the ccdd builtin command that is
                      not a directory is assumed to be the name of a  variable
                      whose value is the directory to change to.
              ccddssppeellll If  set, the ccdd command attempts to correct minor errors
                      in the spelling of a directory component.  Minor  errors
                      include  transposed characters, a missing character, and
                      one extra character.  If ccdd corrects the directory name,
                      it prints the corrected filename, and the  command  pro-
                      ceeds.  This option is only used by interactive shells.
              cchheecckkhhaasshh
                      If set, bbaasshh checks that a command found in the hash ta-
                      ble  exists  before  trying  to execute it.  If a hashed
                      command no longer exists, bbaasshh performs  a  normal  path
                      search.
              cchheecckkjjoobbss
                      If set, bbaasshh lists the status of any stopped and running
                      jobs  before  exiting an interactive shell.  If any jobs
                      are running, bbaasshh defers the exit until a second exit is
                      attempted without an intervening command (see  JJOOBB  CCOONN--
                      TTRROOLL  above).  The shell always postpones exiting if any
                      jobs are stopped.
              cchheecckkwwiinnssiizzee
                      If set, bbaasshh checks the window size after each  external
                      (non-builtin)  command  and,  if  necessary, updates the
                      values of LLIINNEESS and CCOOLLUUMMNNSS, using the  file  descriptor
                      associated  with the standard error if it is a terminal.
                      This option is enabled by default.
              ccmmddhhiisstt If set, bbaasshh attempts to save all lines of  a  multiple-
                      line  command  in  the  same history entry.  This allows
                      easy re-editing of multi-line commands.  This option  is
                      enabled  by  default,  but only has an effect if command
                      history is enabled, as described above under HHIISSTTOORRYY.
              ccoommppaatt3311
              ccoommppaatt3322
              ccoommppaatt4400
              ccoommppaatt4411
              ccoommppaatt4422
              ccoommppaatt4433
              ccoommppaatt4444
                      These control aspects of the shell's compatibility  mode
                      (see SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE below).
              ccoommpplleettee__ffuullllqquuoottee
                      If  set,  bbaasshh  quotes all shell metacharacters in file-
                      names and directory names  when  performing  completion.
                      If not set, bbaasshh removes metacharacters such as the dol-
                      lar  sign from the set of characters that will be quoted
                      in completed filenames when these metacharacters  appear
                      in  shell  variable references in words to be completed.
                      This means that dollar signs in variable names that  ex-
                      pand  to  directories  will  not be quoted; however, any
                      dollar signs appearing in filenames will not be  quoted,
                      either.   This  is  active only when bash is using back-
                      slashes to quote completed filenames.  This variable  is
                      set  by  default,  which is the default bash behavior in
                      versions through 4.2.
              ddiirreexxppaanndd
                      If set, bbaasshh replaces directory names with  the  results
                      of  word  expansion when performing filename completion.
                      This  changes  the  contents  of  the  rreeaaddlliinnee  editing
                      buffer.   If not set, bbaasshh attempts to preserve what the
                      user typed.
              ddiirrssppeellll
                      If set, bbaasshh attempts spelling correction  on  directory
                      names  during word completion if the directory name ini-
                      tially supplied does not exist.
              ddoottgglloobb If set, bbaasshh includes filenames beginning with a "."  in
                      the  results of pathname expansion.  The filenames _. and
                      _._. must always be matched explicitly, even if ddoottgglloobb is
                      set.
              eexxeeccffaaiill
                      If set, a non-interactive shell will not exit if it can-
                      not execute the file specified as  an  argument  to  the
                      eexxeecc  builtin.   An  interactive  shell does not exit if
                      eexxeecc fails.
              eexxppaanndd__aalliiaasseess
                      If set, aliases are expanded as  described  above  under
                      AALLIIAASSEESS.  This option is enabled by default for interac-
                      tive shells.
              eexxttddeebbuugg
                      If  set at shell invocation, or in a shell startup file,
                      arrange to execute the debugger profile before the shell
                      starts, identical to the ----ddeebbuuggggeerr option.  If set  af-
                      ter  invocation,  behavior intended for use by debuggers
                      is enabled:
                      11..     The --FF option to the ddeeccllaarree builtin displays the
                             source file name and line number corresponding to
                             each function name supplied as an argument.
                      22..     If the command run by the DDEEBBUUGG  trap  returns  a
                             non-zero  value,  the next command is skipped and
                             not executed.
                      33..     If the command run by the DDEEBBUUGG  trap  returns  a
                             value  of 2, and the shell is executing in a sub-
                             routine (a shell function or a shell script  exe-
                             cuted  by  the  ..  or ssoouurrccee builtins), the shell
                             simulates a call to rreettuurrnn.
                      44..     BBAASSHH__AARRGGCC and BBAASSHH__AARRGGVV are updated as  described
                             in their descriptions above).
                      55..     Function  tracing  is  enabled: command substitu-
                             tion, shell functions, and subshells invoked with
                             (( _c_o_m_m_a_n_d )) inherit the DDEEBBUUGG and RREETTUURRNN traps.
                      66..     Error tracing is enabled:  command  substitution,
                             shell  functions,  and  subshells  invoked with ((
                             _c_o_m_m_a_n_d )) inherit the EERRRR trap.
              eexxttgglloobb If set, enable the extended  pattern  matching  features
                      described above under PPaatthhnnaammee EExxppaannssiioonn.
              eexxttqquuoottee
                      If  set,  $$'_s_t_r_i_n_g'  and  $$"_s_t_r_i_n_g" quoting is performed
                      within  $${{_p_a_r_a_m_e_t_e_r}}  expansions  enclosed   in   double
                      quotes.  This option is enabled by default.
              ffaaiillgglloobb
                      If  set,  patterns  which fail to match filenames during
                      pathname expansion result in an expansion error.
              ffoorrccee__ffiiggnnoorree
                      If set, the suffixes  specified  by  the  FFIIGGNNOORREE  shell
                      variable  cause words to be ignored when performing word
                      completion even if the ignored words are the only possi-
                      ble completions.  See SShheellll VVaarriiaabblleess above  for  a  de-
                      scription  of  FFIIGGNNOORREE.   This  option is enabled by de-
                      fault.
              gglloobbaasscciiiirraannggeess
                      If set,  range  expressions  used  in  pattern  matching
                      bracket  expressions (see PPaatttteerrnn MMaattcchhiinngg above) behave
                      as if in the traditional C locale when  performing  com-
                      parisons.   That  is, pattern matching does not take the
                      current locale's collating sequence into account,  so  bb
                      will  not  collate  between  AA and BB, and upper-case and
                      lower-case ASCII characters will collate together.
              gglloobbsskkiippddoottss
                      If set, pathname expansion will never  match  the  file-
                      names  _.  and _._., even if the pattern begins with a ".".
                      This option is enabled by default.
              gglloobbssttaarr
                      If set, the pattern **** used in a pathname expansion con-
                      text will match all files and zero or  more  directories
                      and  subdirectories.  If the pattern is followed by a //,
                      only directories and subdirectories match.
              ggnnuu__eerrrrffmmtt
                      If set, shell error messages are written in the standard
                      GNU error message format.
              hhiissttaappppeenndd
                      If set, the history list is appended to the  file  named
                      by the value of the HHIISSTTFFIILLEE variable when the shell ex-
                      its, rather than overwriting the file.
              hhiissttrreeeeddiitt
                      If  set,  and  rreeaaddlliinnee is being used, the user is given
                      the opportunity to re-edit a  failed  history  substitu-
                      tion.
              hhiissttvveerriiffyy
                      If  set, and rreeaaddlliinnee is being used, the results of his-
                      tory substitution are  not  immediately  passed  to  the
                      shell  parser.   Instead,  the  resulting line is loaded
                      into the rreeaaddlliinnee editing buffer, allowing further modi-
                      fication.
              hhoossttccoommpplleettee
                      If set, and rreeaaddlliinnee is being used, bbaasshh will attempt to
                      perform hostname completion when a word containing  a  @@
                      is   being  completed  (see  CCoommpplleettiinngg  under  RREEAADDLLIINNEE
                      above).  This is enabled by default.
              hhuuppoonneexxiitt
                      If set, bbaasshh will send SSIIGGHHUUPP to all jobs when an inter-
                      active login shell exits.
              iinnhheerriitt__eerrrreexxiitt
                      If set, command substitution inherits the value  of  the
                      eerrrreexxiitt  option, instead of unsetting it in the subshell
                      environment.  This option is enabled when posix mode  is
                      enabled.
              iinntteerraaccttiivvee__ccoommmmeennttss
                      In  an interactive shell, a word beginning with ## causes
                      that word and all remaining characters on that  line  to
                      be  ignored, as in a non-interactive shell (see CCOOMMMMEENNTTSS
                      above).  This option is enabled by default.
              llaassttppiippee
                      If set, and job control is not active,  the  shell  runs
                      the last command of a pipeline not executed in the back-
                      ground in the current shell environment.
              lliitthhiisstt If  set,  and  the ccmmddhhiisstt option is enabled, multi-line
                      commands are saved to the history with embedded newlines
                      rather than using semicolon separators where possible.
              llooccaallvvaarr__iinnhheerriitt
                      If set, local variables inherit the value and attributes
                      of a variable of the same name that exists at a previous
                      scope before any new value is assigned.  The nameref at-
                      tribute is not inherited.
              llooccaallvvaarr__uunnsseett
                      If set, calling uunnsseett on  local  variables  in  previous
                      function  scopes  marks  them so subsequent lookups find
                      them unset until that function returns.  This is identi-
                      cal to the behavior of unsetting local variables at  the
                      current function scope.
              llooggiinn__sshheellll
                      The  shell  sets this option if it is started as a login
                      shell (see IINNVVOOCCAATTIIOONN above).   The  value  may  not  be
                      changed.
              mmaaiillwwaarrnn
                      If  set,  and  a file that bbaasshh is checking for mail has
                      been accessed since the last time it was  checked,  bbaasshh
                      displays  the  message  "The  mail  in _m_a_i_l_f_i_l_e has been
                      read".
              nnoo__eemmppttyy__ccmmdd__ccoommpplleettiioonn
                      If set, and rreeaaddlliinnee is being used, bbaasshh does not search
                      PPAATTHH for possible completions  when  completion  is  at-
                      tempted on an empty line.
              nnooccaasseegglloobb
                      If  set,  bbaasshh  matches  filenames in a case-insensitive
                      fashion when performing pathname expansion (see PPaatthhnnaammee
                      EExxppaannssiioonn above).
              nnooccaasseemmaattcchh
                      If set, bbaasshh  matches  patterns  in  a  case-insensitive
                      fashion when performing matching while executing ccaassee or
                      [[[[ conditional commands, when performing pattern substi-
                      tution  word expansions, or when filtering possible com-
                      pletions as part of programmable completion.
              nnooeexxppaanndd__ttrraannssllaattiioonn
                      If set, bbaasshh encloses the translated results  of  $$""...""
                      quoting  in  single quotes instead of double quotes.  If
                      the string is not translated, this has no effect.
              nnuullllgglloobb
                      If set, pathname expansion patterns which match no files
                      (see PPaatthhnnaammee EExxppaannssiioonn above) expand to nothing and are
                      removed, rather than expanding to themselves.
              ppaattssuubb__rreeppllaacceemmeenntt
                      If set, bbaasshh expands occurrences of && in the replacement
                      string of pattern substitution to the  text  matched  by
                      the  pattern,  as  described  under  PPaarraammeetteerr EExxppaannssiioonn
                      above.  This option is enabled by default.
              pprrooggccoommpp
                      If set, enable the  programmable  completion  facilities
                      (see PPrrooggrraammmmaabbllee CCoommpplleettiioonn above).  This option is en-
                      abled by default.
              pprrooggccoommpp__aalliiaass
                      If  set,  and  programmable  completion is enabled, bbaasshh
                      treats a command name that doesn't have any  completions
                      as a possible alias and attempts alias expansion.  If it
                      has  an alias, bbaasshh attempts programmable completion us-
                      ing the command word resulting from the expanded alias.
              pprroommppttvvaarrss
                      If set, prompt strings undergo parameter expansion, com-
                      mand substitution, arithmetic expansion, and  quote  re-
                      moval  after  being  expanded  as described in PPRROOMMPPTTIINNGG
                      above.  This option is enabled by default.
              rreessttrriicctteedd__sshheellll
                      The shell sets this option  if  it  is  started  in  re-
                      stricted  mode  (see RREESSTTRRIICCTTEEDD SSHHEELLLL below).  The value
                      may not be changed.  This is not reset when the  startup
                      files  are  executed, allowing the startup files to dis-
                      cover whether or not a shell is restricted.
              sshhiifftt__vveerrbboossee
                      If set, the sshhiifftt builtin prints an error  message  when
                      the shift count exceeds the number of positional parame-
                      ters.
              ssoouurrcceeppaatthh
                      If set, the .. (ssoouurrccee) builtin uses the value of PPAATTHH to
                      find  the  directory  containing the file supplied as an
                      argument when the --pp option is not supplied.   This  op-
                      tion is enabled by default.
              vvaarrrreeddiirr__cclloossee
                      If  set, the shell automatically closes file descriptors
                      assigned using the  _{_v_a_r_n_a_m_e_}  redirection  syntax  (see
                      RREEDDIIRREECCTTIIOONN above) instead of leaving them open when the
                      command completes.
              xxppgg__eecchhoo
                      If  set,  the  eecchhoo builtin expands backslash-escape se-
                      quences by default.  If the ppoossiixx shell option  is  also
                      enabled, eecchhoo does not interpret any options.

       ssuussppeenndd [--ff]
              Suspend  the execution of this shell until it receives a SSIIGGCCOONNTT
              signal.  A login shell, or a shell without job control  enabled,
              cannot  be suspended; the --ff option will override this and force
              the suspension.  The return status is 0 unless the  shell  is  a
              login  shell  or  job  control is not enabled and --ff is not sup-
              plied.

       tteesstt _e_x_p_r
       [[ _e_x_p_r ]]
              Return a status of 0 (true) or 1 (false) depending on the evalu-
              ation of the conditional expression  _e_x_p_r.   Each  operator  and
              operand  must  be a separate argument.  Expressions are composed
              of the primaries described above under CCOONNDDIITTIIOONNAALL  EEXXPPRREESSSSIIOONNSS.
              tteesstt  does not accept any options, nor does it accept and ignore
              an argument of ---- as signifying the end of options.

              Expressions may  be  combined  using  the  following  operators,
              listed  in  decreasing  order of precedence.  The evaluation de-
              pends on the number of arguments; see below.  tteesstt uses operator
              precedence when there are five or more arguments.
              !! _e_x_p_r True if _e_x_p_r is false.
              (( _e_x_p_r ))
                     Returns the value of _e_x_p_r.  This may be used to  override
                     normal operator precedence.
              _e_x_p_r_1 -aa _e_x_p_r_2
                     True if both _e_x_p_r_1 and _e_x_p_r_2 are true.
              _e_x_p_r_1 -oo _e_x_p_r_2
                     True if either _e_x_p_r_1 or _e_x_p_r_2 is true.

              tteesstt and [[ evaluate conditional expressions using a set of rules
              based on the number of arguments.

              0 arguments
                     The expression is false.
              1 argument
                     The expression is true if and only if the argument is not
                     null.
              2 arguments
                     If the first argument is !!, the expression is true if and
                     only  if the second argument is null.  If the first argu-
                     ment is one of the  unary  conditional  operators  listed
                     above  under  CCOONNDDIITTIIOONNAALL  EEXXPPRREESSSSIIOONNSS, the expression is
                     true if the unary test is true.  If the first argument is
                     not a valid unary conditional operator, the expression is
                     false.
              3 arguments
                     The following conditions are applied in the order listed.
                     If the second argument is one of the  binary  conditional
                     operators listed above under CCOONNDDIITTIIOONNAALL EEXXPPRREESSSSIIOONNSS, the
                     result of the expression is the result of the binary test
                     using  the first and third arguments as operands.  The --aa
                     and --oo operators are  considered  binary  operators  when
                     there  are  three arguments.  If the first argument is !!,
                     the value is the negation of the two-argument test  using
                     the second and third arguments.  If the first argument is
                     exactly (( and the third argument is exactly )), the result
                     is  the one-argument test of the second argument.  Other-
                     wise, the expression is false.
              4 arguments
                     The following conditions are applied in the order listed.
                     If the first argument is !!, the result is the negation of
                     the three-argument expression composed of  the  remaining
                     arguments.   If  the  first argument is exactly (( and the
                     fourth argument is exactly )), the result is the two-argu-
                     ment test of the second and third arguments.   Otherwise,
                     the  expression  is  parsed  and  evaluated  according to
                     precedence using the rules listed above.
              5 or more arguments
                     The expression  is  parsed  and  evaluated  according  to
                     precedence using the rules listed above.

              When the shell is in posix mode, or if the expression is part of
              the [[[[ command, the << and >> operators sort using the current lo-
              cale.   If  the  shell is not in posix mode, the tteesstt and [[ com-
              mands sort lexicographically using ASCII ordering.

              The historical operator-precedence parsing with 4 or more  argu-
              ments  can  lead  to ambiguities when it encounters strings that
              look like primaries.  The POSIX standard has deprecated  the  --aa
              and  --oo  primaries and enclosing expressions within parentheses.
              Scripts should no longer use them.  It's much more  reliable  to
              restrict  test  invocations  to a single primary, and to replace
              uses of --aa and --oo with the shell's &&&& and |||| list operators.

       ttiimmeess  Print the accumulated user and system times for  the  shell  and
              for processes run from the shell.  The return status is 0.

       ttrraapp [--llppPP] [[_a_c_t_i_o_n] _s_i_g_s_p_e_c ...]
              The _a_c_t_i_o_n is a command that is read and executed when the shell
              receives  any  of the signals _s_i_g_s_p_e_c.  If _a_c_t_i_o_n is absent (and
              there is a single _s_i_g_s_p_e_c) or --, each specified _s_i_g_s_p_e_c is reset
              to the value it had when the shell was started.   If  _a_c_t_i_o_n  is
              the  null string the signal specified by each _s_i_g_s_p_e_c is ignored
              by the shell and by the commands it invokes.

              If no arguments are supplied, ttrraapp displays the actions  associ-
              ated with each trapped signal as a set of ttrraapp commands that can
              be  reused as shell input to restore the current signal disposi-
              tions.  If --pp is given, and _a_c_t_i_o_n is  not  present,  then  ttrraapp
              displays  the  actions  associated with each _s_i_g_s_p_e_c or, if none
              are supplied, for all trapped signals, as a set of ttrraapp commands
              that can be reused as shell input to restore the current  signal
              dispositions.   The  --PP  option  behaves similarly, but displays
              only the actions associated with each _s_i_g_s_p_e_c argument.  --PP  re-
              quires  at least one _s_i_g_s_p_e_c argument.  The --PP or --pp options may
              be used in a subshell environment (e.g.,  command  substitution)
              and,  as  long  as they are used before ttrraapp is used to change a
              signal's handling, will display the state of its parent's traps.

              The --ll option prints a list of signal  names  and  their  corre-
              sponding  numbers.  Each _s_i_g_s_p_e_c is either a signal name defined
              in <_s_i_g_n_a_l_._h>, or a signal number.  Signal names are case insen-
              sitive and the SSIIGG prefix is optional.  If --ll is  supplied  with
              no _s_i_g_s_p_e_c arguments, it prints a list of valid signal names.

              If  a  _s_i_g_s_p_e_c  is EEXXIITT (0), _a_c_t_i_o_n is executed on exit from the
              shell.  If a _s_i_g_s_p_e_c is DDEEBBUUGG, _a_c_t_i_o_n is executed  before  every
              _s_i_m_p_l_e  _c_o_m_m_a_n_d,  _f_o_r  command, _c_a_s_e command, _s_e_l_e_c_t command, ((
              arithmetic command, [[ conditional command, arithmetic _f_o_r  com-
              mand,  and before the first command executes in a shell function
              (see SSHHEELLLL GGRRAAMMMMAARR above).  Refer  to  the  description  of  the
              eexxttddeebbuugg  shell  option (see sshhoopptt above) for details of its ef-
              fect on the DDEEBBUUGG trap.  If a _s_i_g_s_p_e_c is RREETTUURRNN, _a_c_t_i_o_n is  exe-
              cuted each time a shell function or a script executed with the ..
              or ssoouurrccee builtins finishes executing.

              If  a  _s_i_g_s_p_e_c  is  EERRRR,  _a_c_t_i_o_n is executed whenever a pipeline
              (which may consist of a single simple command),  a  list,  or  a
              compound  command returns a non-zero exit status, subject to the
              following conditions.  The EERRRR  trap  is  not  executed  if  the
              failed command is part of the command list immediately following
              a wwhhiillee or uunnttiill reserved word, part of the test in an _i_f state-
              ment,  part  of a command executed in a &&&& or |||| list except the
              command following the final &&&& or ||||, any command in a  pipeline
              but  the  last  (subject  to the state of the ppiippeeffaaiill shell op-
              tion), or if the command's return value is being inverted  using
              !!.  These are the same conditions obeyed by the eerrrreexxiitt (--ee) op-
              tion.

              When the shell is not interactive, signals ignored upon entry to
              the shell cannot be trapped or reset.  Interactive shells permit
              trapping signals ignored on entry.  Trapped signals that are not
              being  ignored  are reset to their original values in a subshell
              or subshell environment when one is created.  The return  status
              is false if any _s_i_g_s_p_e_c is invalid; otherwise ttrraapp returns true.

       ttrruuee   Does nothing, returns a 0 status.

       ttyyppee [--aaffttppPP] _n_a_m_e [_n_a_m_e ...]
              Indicate how each _n_a_m_e would be interpreted if used as a command
              name.

              If  the  --tt option is used, ttyyppee prints a string which is one of
              _a_l_i_a_s, _k_e_y_w_o_r_d, _f_u_n_c_t_i_o_n, _b_u_i_l_t_i_n, or _f_i_l_e if _n_a_m_e is an  alias,
              shell  reserved word, function, builtin, or executable file, re-
              spectively.  If the _n_a_m_e is not found, ttyyppee prints  nothing  and
              returns a non-zero exit status.

              If  the  --pp  option is used, ttyyppee either returns the pathname of
              the executable file that would be found by searching  $$PPAATTHH  for
              _n_a_m_e or nothing if "type -t name" would not return _f_i_l_e.  The --PP
              option  forces  a  PPAATTHH  search  for each _n_a_m_e, even if "type -t
              name" would not return _f_i_l_e.  If _n_a_m_e is present in the table of
              hashed commands, --pp and --PP print the hashed value, which is  not
              necessarily the file that appears first in PPAATTHH.

              If  the  --aa  option  is used, ttyyppee prints all of the places that
              contain a command named _n_a_m_e.  This includes  aliases,  reserved
              words,  functions, and builtins, but the path search options (--pp
              and --PP) can be supplied to restrict  the  output  to  executable
              files.   ttyyppee does not consult the table of hashed commands when
              using --aa with --pp, and only performs a PPAATTHH search for _n_a_m_e.

              The --ff option suppresses shell function lookup, as with the ccoomm--
              mmaanndd builtin.  ttyyppee returns true if all  of  the  arguments  are
              found, false if any are not found.

       uulliimmiitt [--HHSS] --aa
       uulliimmiitt [--HHSS] [--bbccddeeffiikkllmmnnppqqrrssttuuvvxxPPRRTT [_l_i_m_i_t]]
              Provides  control  over the resources available to the shell and
              to processes it starts, on systems that allow such control.

              The --HH and --SS options specify whether the hard or soft limit  is
              set for the given resource.  A hard limit cannot be increased by
              a non-root user once it is set; a soft limit may be increased up
              to  the value of the hard limit.  If neither --HH nor --SS is speci-
              fied, uulliimmiitt sets both the soft and hard limits.

              The value of _l_i_m_i_t can be a number in the unit specified for the
              resource or one of the special values hhaarrdd, ssoofftt, or  uunnlliimmiitteedd,
              which  stand for the current hard limit, the current soft limit,
              and no limit, respectively.  If _l_i_m_i_t is omitted, uulliimmiitt  prints
              the  current value of the soft limit of the resource, unless the
              --HH option is given.  When more than one resource  is  specified,
              the  limit name and unit, if appropriate, are printed before the
              value.  Other options are interpreted as follows:
              --aa     Report all current limits; no limits are set.
              --bb     The maximum socket buffer size.
              --cc     The maximum size of core files created.
              --dd     The maximum size of a process's data segment.
              --ee     The maximum scheduling priority ("nice").
              --ff     The maximum size of files written by the  shell  and  its
                     children.
              --ii     The maximum number of pending signals.
              --kk     The maximum number of kqueues that may be allocated.
              --ll     The maximum size that may be locked into memory.
              --mm     The  maximum resident set size (many systems do not honor
                     this limit).
              --nn     The maximum number of open file descriptors (most systems
                     do not allow this value to be set).
              --pp     The pipe size in 512-byte blocks (this may not be set).
              --qq     The maximum number of bytes in POSIX message queues.
              --rr     The maximum real-time scheduling priority.
              --ss     The maximum stack size.
              --tt     The maximum amount of cpu time in seconds.
              --uu     The maximum number of processes  available  to  a  single
                     user.
              --vv     The  maximum  amount  of  virtual memory available to the
                     shell and, on some systems, to its children.
              --xx     The maximum number of file locks.
              --PP     The maximum number of pseudoterminals.
              --RR     The maximum time  a  real-time  process  can  run  before
                     blocking, in microseconds.
              --TT     The maximum number of threads.

              If  _l_i_m_i_t  is  supplied, and the --aa option is not used, _l_i_m_i_t is
              the new value of the specified resource.  If no option  is  sup-
              plied, then --ff is assumed.

              Values  are  in 1024-byte increments, except for --tt, which is in
              seconds; --RR, which is in microseconds; --pp, which is in units  of
              512-byte  blocks; --PP, --TT, --bb, --kk, --nn, and --uu, which are unscaled
              values; and, when in  posix  mode,  --cc  and  --ff,  which  are  in
              512-byte  increments.   The return status is 0 unless an invalid
              option or argument is supplied, or an error occurs while setting
              a new limit.

       uummaasskk [--pp] [--SS] [_m_o_d_e]
              Set the user file-creation mask to _m_o_d_e.  If _m_o_d_e begins with  a
              digit, it is interpreted as an octal number; otherwise it is in-
              terpreted  as  a  symbolic mode mask similar to that accepted by
              _c_h_m_o_d(1).  If _m_o_d_e is omitted, uummaasskk prints the current value of
              the mask.  The --SS option without a _m_o_d_e argument prints the mask
              in a symbolic format; the default output is an octal number.  If
              the --pp option is supplied, and _m_o_d_e is omitted, the output is in
              a form that may be reused as input.  The return status  is  zero
              if  the mode was successfully changed or if no _m_o_d_e argument was
              supplied, and non-zero otherwise.

       uunnaalliiaass [-aa] [_n_a_m_e ...]
              Remove each _n_a_m_e from the list of defined  aliases.   If  --aa  is
              supplied,  remove  all  alias  definitions.  The return value is
              true unless a supplied _n_a_m_e is not a defined alias.

       uunnsseett [-ffvv] [-nn] [_n_a_m_e ...]
              For each _n_a_m_e, remove the corresponding  variable  or  function.
              If the --vv option is given, each _n_a_m_e refers to a shell variable,
              and  that  variable  is  removed.  If --ff is specified, each _n_a_m_e
              refers to a shell function, and the function definition  is  re-
              moved.   If  the  --nn  option is supplied, and _n_a_m_e is a variable
              with the _n_a_m_e_r_e_f attribute, _n_a_m_e will be unset rather  than  the
              variable  it  references.   --nn has no effect if the --ff option is
              supplied.  Read-only variables and functions may not  be  unset.
              When  variables  or functions are removed, they are also removed
              from the environment passed to subsequent commands.  If  no  op-
              tions  are supplied, each _n_a_m_e refers to a variable; if there is
              no variable by that name, a function with that name, if any,  is
              unset.   Some  shell  variables  may  not  be  unset.  If any of
              BBAASSHH__AALLIIAASSEESS,  BBAASSHH__AARRGGVV00,  BBAASSHH__CCMMDDSS,  BBAASSHH__CCOOMMMMAANNDD,  BBAASSHH__SSUUBB--
              SSHHEELLLL,   BBAASSHHPPIIDD,   CCOOMMPP__WWOORRDDBBRREEAAKKSS,   DDIIRRSSTTAACCKK,  EEPPOOCCHHRREEAALLTTIIMMEE,
              EEPPOOCCHHSSEECCOONNDDSS, FFUUNNCCNNAAMMEE, GGRROOUUPPSS, HHIISSTTCCMMDD,  LLIINNEENNOO,  RRAANNDDOOMM,  SSEECC--
              OONNDDSS,  or SSRRAANNDDOOMM are unset, they lose their special properties,
              even if they are subsequently reset.  The exit  status  is  true
              unless a _n_a_m_e is readonly or may not be unset.

       wwaaiitt [--ffnn] [--pp _v_a_r_n_a_m_e] [_i_d ...]
              Wait for each specified child process _i_d and return the termina-
              tion  status of the last _i_d.  Each _i_d may be a process ID _p_i_d or
              a job specification _j_o_b_s_p_e_c; if  a  jobspec  is  supplied,  wwaaiitt
              waits for all processes in the job.

              If  no  options  or _i_ds are supplied, wwaaiitt waits for all running
              background jobs and the last-executed process  substitution,  if
              its process id is the same as $$!!, and the return status is zero.

              If  the  --nn  option  is  supplied, wwaaiitt waits for any one of the
              given _i_ds or, if no _i_ds are supplied, any job or process substi-
              tution, to complete and returns its exit status.  If none of the
              supplied _i_ds is a child of the shell, or if no _i_ds are  supplied
              and  the  shell has no unwaited-for children, the exit status is
              127.

              If the --pp option is supplied, wwaaiitt assigns the  process  or  job
              identifier  of  the job for which the exit status is returned to
              the variable _v_a_r_n_a_m_e named by the option  argument.   The  vari-
              able,  which cannot be readonly, will be unset initially, before
              any assignment.  This is useful only when used with the  --nn  op-
              tion.

              Supplying  the  --ff  option,  when job control is enabled, forces
              wwaaiitt to wait for each _i_d to terminate before returning its  sta-
              tus, instead of returning when it changes status.

              If  none  of  the  _i_ds  specify  one of the shell's active child
              processes, the return status is 127.  If wwaaiitt is interrupted  by
              a  signal,  any _v_a_r_n_a_m_e will remain unset, and the return status
              will be greater than 128,  as  described  under  SSIIGGNNAALLSS  above.
              Otherwise, the return status is the exit status of the last _i_d.

SSHHEELLLL CCOOMMPPAATTIIBBIILLIITTYY MMOODDEE
       Bash-4.0  introduced the concept of a _s_h_e_l_l _c_o_m_p_a_t_i_b_i_l_i_t_y _l_e_v_e_l, speci-
       fied as a set of options to the shopt builtin (ccoommppaatt3311, ccoommppaatt3322, ccoomm--
       ppaatt4400, ccoommppaatt4411, and so on).  There is only one  current  compatibility
       level -- each option is mutually exclusive.  The compatibility level is
       intended  to allow users to select behavior from previous versions that
       is incompatible with newer versions while they migrate scripts  to  use
       current  features  and behavior.  It's intended to be a temporary solu-
       tion.

       This section does not mention behavior that is standard for a  particu-
       lar  version  (e.g., setting ccoommppaatt3322 means that quoting the right hand
       side of the regexp matching operator quotes special  regexp  characters
       in  the word, which is default behavior in bash-3.2 and subsequent ver-
       sions).

       If a user enables, say, ccoommppaatt3322, it may affect the behavior  of  other
       compatibility  levels  up  to  and  including the current compatibility
       level.  The idea is that each  compatibility  level  controls  behavior
       that  changed  in that version of bbaasshh, but that behavior may have been
       present in earlier versions.  For instance, the change to  use  locale-
       based  comparisons  with  the  [[[[ command came in bash-4.1, and earlier
       versions used ASCII-based comparisons, so enabling ccoommppaatt3322 will enable
       ASCII-based comparisons as well.  That granularity may  not  be  suffi-
       cient  for  all uses, and as a result users should employ compatibility
       levels carefully.  Read the documentation for a particular  feature  to
       find out the current behavior.

       Bash-4.3  introduced  a new shell variable: BBAASSHH__CCOOMMPPAATT.  The value as-
       signed to this variable (a decimal version number like 4.2, or an inte-
       ger corresponding to the ccoommppaatt_N_N option, like 42) determines the  com-
       patibility level.

       Starting with bash-4.4, bbaasshh began deprecating older compatibility lev-
       els.  Eventually, the options will be removed in favor of BBAASSHH__CCOOMMPPAATT.

       Bash-5.0  was the final version for which there was an individual shopt
       option for the previous version.  BBAASSHH__CCOOMMPPAATT is the only mechanism  to
       control the compatibility level in versions newer than bash-5.0.

       The  following  table describes the behavior changes controlled by each
       compatibility level setting.  The ccoommppaatt_N_N tag is used as shorthand for
       setting the compatibility level to _N_N using one of the following mecha-
       nisms.  For versions prior to bash-5.0, the compatibility level may  be
       set  using  the  corresponding ccoommppaatt_N_N shopt option.  For bash-4.3 and
       later versions, the BBAASSHH__CCOOMMPPAATT variable is preferred, and  it  is  re-
       quired for bash-5.1 and later versions.

       ccoommppaatt3311
              +o      Quoting the rhs of the [[[[ command's regexp matching oper-
                     ator (=~) has no special effect.

       ccoommppaatt3322
              +o      The  <<  and >> operators to the [[[[ command do not consider
                     the current locale when comparing strings; they use ASCII
                     ordering.

       ccoommppaatt4400
              +o      The << and >> operators to the [[[[ command do  not  consider
                     the current locale when comparing strings; they use ASCII
                     ordering.  BBaasshh versions prior to bash-4.1 use ASCII col-
                     lation  and _s_t_r_c_m_p(3); bash-4.1 and later use the current
                     locale's collation sequence and _s_t_r_c_o_l_l(3).

       ccoommppaatt4411
              +o      In posix mode, ttiimmee may be followed by options and  still
                     be recognized as a reserved word (this is POSIX interpre-
                     tation 267).
              +o      In _p_o_s_i_x mode, the parser requires that an even number of
                     single  quotes  occur  in  the  _w_o_r_d portion of a double-
                     quoted parameter expansion and treats them specially,  so
                     that  characters  within the single quotes are considered
                     quoted (this is POSIX interpretation 221).

       ccoommppaatt4422
              +o      The replacement string in double-quoted pattern substitu-
                     tion does not undergo quote removal, as it does  in  ver-
                     sions after bash-4.2.
              +o      In  posix mode, single quotes are considered special when
                     expanding the _w_o_r_d portion of a  double-quoted  parameter
                     expansion  and  can  be  used to quote a closing brace or
                     other special character (this is part of POSIX  interpre-
                     tation  221);  in  later  versions, single quotes are not
                     special within double-quoted word expansions.

       ccoommppaatt4433
              +o      Word expansion errors  are  considered  non-fatal  errors
                     that  cause  the  current  command to fail, even in posix
                     mode (the default behavior is to make them  fatal  errors
                     that cause the shell to exit).
              +o      When   executing   a   shell  function,  the  loop  state
                     (while/until/etc.)  is not reset, so bbrreeaakk or ccoonnttiinnuuee in
                     that function will break or continue loops in the calling
                     context.  Bash-4.4 and later reset the loop state to pre-
                     vent this.

       ccoommppaatt4444
              +o      The shell sets  up  the  values  used  by  BBAASSHH__AARRGGVV  and
                     BBAASSHH__AARRGGCC  so  they  can expand to the shell's positional
                     parameters even if extended debugging  mode  is  not  en-
                     abled.
              +o      A  subshell  inherits  loops  from its parent context, so
                     bbrreeaakk or  ccoonnttiinnuuee  will  cause  the  subshell  to  exit.
                     Bash-5.0  and  later  reset the loop state to prevent the
                     exit
              +o      Variable assignments preceding builtins like  eexxppoorrtt  and
                     rreeaaddoonnllyy that set attributes continue to affect variables
                     with the same name in the calling environment even if the
                     shell is not in posix mode.

       ccoommppaatt5500
              +o      Bash-5.1  changed  the way $$RRAANNDDOOMM is generated to intro-
                     duce slightly more randomness.  If the shell  compatibil-
                     ity level is set to 50 or lower, it reverts to the method
                     from  bash-5.0 and previous versions, so seeding the ran-
                     dom number generator by assigning a value to RRAANNDDOOMM  will
                     produce the same sequence as in bash-5.0.
              +o      If  the  command hash table is empty, bash versions prior
                     to bash-5.1 printed an informational message to that  ef-
                     fect,  even  when  producing output that can be reused as
                     input.  Bash-5.1 suppresses that message when the --ll  op-
                     tion is supplied.

       ccoommppaatt5511
              +o      The  uunnsseett  builtin  treats  attempts to unset array sub-
                     scripts @@ and ** differently depending on whether the  ar-
                     ray  is  indexed  or associative, and differently than in
                     previous versions.
              +o      Arithmetic commands ( ((((...)))) ) and the expressions in an
                     arithmetic for statement can be expanded more than once.
              +o      Expressions used as arguments to arithmetic operators  in
                     the  [[[[  conditional  command  can  be expanded more than
                     once.
              +o      The expressions in substring  parameter  brace  expansion
                     can be expanded more than once.
              +o      The expressions in the $$((((...)))) word expansion can be ex-
                     panded more than once.
              +o      Arithmetic  expressions  used as indexed array subscripts
                     can be expanded more than once.
              +o      tteesstt --vv, when given an argument of AA[[@@]], where  AA  is  an
                     existing associative array, will return true if the array
                     has  any set elements.  Bash-5.2 will look for and report
                     on a key named @@.
              +o      The  ${_p_a_r_a_m_e_t_e_r[[::]]==_v_a_l_u_e}  word  expansion  will  return
                     _v_a_l_u_e,  before any variable-specific transformations have
                     been performed (e.g., converting to lowercase).  Bash-5.2
                     will return the final value assigned to the variable.
              +o      Parsing command substitutions will behave as if  extended
                     globbing (see the description of the sshhoopptt builtin above)
                     is  enabled,  so that parsing a command substitution con-
                     taining an extglob pattern (say, as part of a shell func-
                     tion) will not fail.  This assumes the intent is  to  en-
                     able  extglob before the command is executed and word ex-
                     pansions are performed.  It will fail at  word  expansion
                     time  if extglob hasn't been enabled by the time the com-
                     mand is executed.

       ccoommppaatt5522
              +o      The tteesstt builtin uses its historical algorithm  to  parse
                     parenthesized  subexpressions when given five or more ar-
                     guments.
              +o      If the --pp or --PP option is supplied to the  bbiinndd  builtin,
                     bbiinndd treats any arguments remaining after option process-
                     ing  as  bindable command names, and displays any key se-
                     quences bound to those commands, instead of treating  the
                     arguments as key sequences to bind.

RREESSTTRRIICCTTEEDD SSHHEELLLL
       If bbaasshh is started with the name rrbbaasshh, or the --rr option is supplied at
       invocation,  the  shell becomes _r_e_s_t_r_i_c_t_e_d.  A restricted shell is used
       to set up an environment more controlled than the standard  shell.   It
       behaves  identically  to bbaasshh with the exception that the following are
       disallowed or not performed:

       +o      Changing directories with ccdd.

       +o      Setting or unsetting the values of SSHHEELLLL, PPAATTHH,  HHIISSTTFFIILLEE,  EENNVV,
              or BBAASSHH__EENNVV.

       +o      Specifying command names containing //.

       +o      Specifying  a  filename  containing  a // as an argument to the ..
              builtin command.

       +o      Using the --pp option to the  ..   builtin  command  to  specify  a
              search path.

       +o      Specifying  a  filename containing a slash as an argument to the
              hhiissttoorryy builtin command.

       +o      Specifying a filename containing a slash as an argument  to  the
              --pp option to the hhaasshh builtin command.

       +o      Importing  function  definitions  from  the shell environment at
              startup.

       +o      Parsing the values of BBAASSHHOOPPTTSS and SSHHEELLLLOOPPTTSS from the shell  en-
              vironment at startup.

       +o      Redirecting  output using the >, >|, <>, >&, &>, and >> redirec-
              tion operators.

       +o      Using the eexxeecc builtin command to replace the shell with another
              command.

       +o      Adding or deleting builtin commands with the --ff and  --dd  options
              to the eennaabbllee builtin command.

       +o      Using  the  eennaabbllee  builtin  command  to  enable  disabled shell
              builtins.

       +o      Specifying the --pp option to the ccoommmmaanndd builtin command.

       +o      Turning off  restricted  mode  with  sseett  ++rr  or  sshhoopptt  --uu  rree--
              ssttrriicctteedd__sshheellll.

       These restrictions are enforced after any startup files are read.

       When a command that is found to be a shell script is executed (see CCOOMM--
       MMAANNDD  EEXXEECCUUTTIIOONN  above),  rrbbaasshh turns off any restrictions in the shell
       spawned to execute the script.

SSEEEE AALLSSOO
       _B_a_s_h _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l, Brian Fox and Chet Ramey
       _T_h_e _G_n_u _R_e_a_d_l_i_n_e _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
       _T_h_e _G_n_u _H_i_s_t_o_r_y _L_i_b_r_a_r_y, Brian Fox and Chet Ramey
       _P_o_r_t_a_b_l_e _O_p_e_r_a_t_i_n_g _S_y_s_t_e_m _I_n_t_e_r_f_a_c_e _(_P_O_S_I_X_) _P_a_r_t _2_: _S_h_e_l_l _a_n_d _U_t_i_l_i_-
       _t_i_e_s, IEEE --
              http://pubs.opengroup.org/onlinepubs/9799919799/
       http://tiswww.case.edu/~chet/bash/POSIX -- a description of posix mode
       _s_h(1), _k_s_h(1), _c_s_h(1)
       _e_m_a_c_s(1), _v_i(1)
       _r_e_a_d_l_i_n_e(3)

FFIILLEESS
       _/_b_i_n_/_b_a_s_h
              The bbaasshh executable
       _/_e_t_c_/_p_r_o_f_i_l_e
              The systemwide initialization file, executed for login shells
       _~_/_._b_a_s_h___p_r_o_f_i_l_e
              The personal initialization file, executed for login shells
       _~_/_._b_a_s_h_r_c
              The individual per-interactive-shell startup file
       _~_/_._b_a_s_h___l_o_g_o_u_t
              The individual login shell cleanup file, executed when  a  login
              shell exits
       _~_/_._b_a_s_h___h_i_s_t_o_r_y
              The  default value of HHIISSTTFFIILLEE, the file in which bash saves the
              command history
       _~_/_._i_n_p_u_t_r_c
              Individual _r_e_a_d_l_i_n_e initialization file

AAUUTTHHOORRSS
       Brian Fox, Free Software Foundation
       bfox@gnu.org

       Chet Ramey, Case Western Reserve University
       chet.ramey@case.edu

BBUUGG RREEPPOORRTTSS
       If you find a bug in bbaasshh, you should report it.  But first, you should
       make sure that it really is a bug, and that it appears  in  the  latest
       version   of  bbaasshh.   The  latest  version  is  always  available  from
       _f_t_p_:_/_/_f_t_p_._g_n_u_._o_r_g_/_p_u_b_/_g_n_u_/_b_a_s_h_/          and          _h_t_t_p_:_/_/_g_i_t_._s_a_v_a_n_-
       _n_a_h_._g_n_u_._o_r_g_/_c_g_i_t_/_b_a_s_h_._g_i_t_/_s_n_a_p_s_h_o_t_/_b_a_s_h_-_m_a_s_t_e_r_._t_a_r_._g_z.

       Once  you  have  determined that a bug actually exists, use the _b_a_s_h_b_u_g
       command to submit a bug report.  If you have a fix, you are  encouraged
       to mail that as well!  You may send suggestions and "philosophical" bug
       reports  to  _b_u_g_-_b_a_s_h_@_g_n_u_._o_r_g  or  post  them  to  the Usenet newsgroup
       ggnnuu..bbaasshh..bbuugg.

       ALL bug reports should include:

       The version number of bbaasshh
       The hardware and operating system
       The compiler used to compile
       A description of the bug behavior
       A short script or "recipe" which exercises the bug

       _b_a_s_h_b_u_g inserts the first three items automatically into  the  template
       it provides for filing a bug report.

       Comments and bug reports concerning this manual page should be directed
       to _c_h_e_t_._r_a_m_e_y_@_c_a_s_e_._e_d_u.

BBUUGGSS
       It's too big and too slow.

       There are some subtle differences between bbaasshh and traditional versions
       of sshh, mostly because of the POSIX specification.

       Aliases are confusing in some uses.

       Shell builtin commands and functions are not stoppable/restartable.

       Compound  commands  and  command  lists of the form "a ; b ; c" are not
       handled gracefully when  combined  with  process  suspension.   When  a
       process  is stopped, the shell immediately executes the next command in
       the list or breaks out of any existing loops.  It suffices  to  enclose
       the  command  in  parentheses to force it into a subshell, which may be
       stopped as a unit, or to start the command in the background and  imme-
       diately bring it into the foreground.

       Array variables may not (yet) be exported.

GNU Bash 5.3                     2025 April 7                          _B_A_S_H(1)
