get_environment_variable in Fortran Wiki

## Description
Get the `value` of the environmental variable `name`.
Note that `get_environment_variable` need not be thread-safe. It
is the responsibility of the user to ensure that the environment is
not being updated concurrently with a call to the
`get_environment_variable` intrinsic.
## Standard
[[Fortran 2003]] and later
## Class
Subroutine
## Syntax
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ {: lang=fortran }
call get_environment_variable(name[, value, length, status, trim_name)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
## Arguments
 - `name` - (Optional) Shall be a scalar of type `character` and of default kind.
 - `value` - (Optional) Shall be a scalar of type `character` and of default kind.
 - `length` - (Optional) Shall be a scalar of type `integer` and of default kind.
 - `status` - (Optional) Shall be a scalar of type `integer` and of default kind.
 - `trim_name` - (Optional) Shall be a scalar of type `logical` and of default kind.
## Return value
Stores the value of `name` in `value`. If `value` is
not large enough to hold the data, it is truncated. If `name`
is not set, `value` will be filled with blanks. Argument `length`
contains the length needed for storing the environment variable `name`
or zero if it is not present. `status` is -1 if `value` is present
but too short for the environment variable; it is 1 if the environment
variable does not exist and 2 if the processor does not support environment
variables; in all other cases `status` is zero. If `trim_name` is
present with the value `.false.`, the trailing blanks in `name`
are significant; otherwise they are not part of the environment variable
name.
## Example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ {: lang=fortran }
program test_getenv
 character(len=255) :: homedir
 call get_environment_variable("HOME", homedir)
 write (*,*) trim(homedir)
end program
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
category: intrinsics