### 36.7 Environment Variables ¶

`val =` getenv `("var")` ¶

  Return the value of the environment variable var.

  For example,

      getenv ("PATH")

  returns a string containing the value of your path.

  See also: setenv, unsetenv, isenv.

`tf =` isenv `(var)` ¶

  Return true if the variable var is an environment variable, and false otherwise.

  For example,

      tf = isenv ("PATH")

  will typically return true on UNIX systems because `"PATH"` is an environment variable for UNIX.

  See also: getenv, setenv, unsetenv.

setenv `("var", value)` ¶
setenv `(var)` ¶
putenv `(…)` ¶

  Set the value of the environment variable var to value.

  If no value is specified then the variable will be assigned the null string.

  Programming Note: `putenv` is an alias for `setenv` and can be used interchangeably.

  See also: unsetenv, getenv, isenv.

unsetenv `("var")` ¶
`status =` unsetenv `("var")` ¶

  Delete the environment variable var.

  Return 0 if the variable was deleted, or did not exist, and -1 if an error occurred.

  See also: setenv, getenv, isenv.

`homedir =` get_home_directory `()` ¶

  Return the current home directory.

  On most systems, this is equivalent to `getenv ("HOME")`. On Windows systems, if the environment variable `HOME` is not set then it is equivalent to `fullfile (getenv ("HOMEDRIVE"), getenv ("HOMEPATH"))`

  See also: getenv.