Manpages - Env.3perl

Env - perl module that imports environment variables as scalars or arrays

use Env; use Env qw(PATH HOME TERM); use Env qw($SHELL @LD_LIBRARY_PATH);

Perl maintains environment variables in a special hash named %ENV. For when this access method is inconvenient, the Perl module Env allows environment variables to be treated as scalar or array variables.

The Env::import() function ties environment variables with suitable names to global Perl variables with the same names. By default it ties all existing environment variables (keys %ENV) to scalars. If the import function receives arguments, it takes them to be a list of variables to tie; it’s okay if they don’t yet exist. The scalar type prefix ’\(' is inferred for any element of this list not prefixed by '\)’ or ’@’. Arrays are implemented in terms of split and join, using $Config::Config{path_sep} as the delimiter.

After an environment variable is tied, merely use it like a normal variable. You may access its value

@path = split(:, $PATH); print join(“\n”, @LD_LIBRARY_PATH), “\n”;

or modify it

$PATH .= “:/any/path”; push @LD_LIBRARY_PATH, $dir;

however you’d like. Bear in mind, however, that each access to a tied array variable requires splitting the environment variable’s string anew.

The code:

use Env qw(@PATH); push @PATH, /any/path;

is almost equivalent to:

use Env qw(PATH); $PATH .= “:/any/path”;

except that if $ENV{PATH} started out empty, the second approach leaves it with the (odd) value “:/any/path, but the first approach leaves it with /any/path”.

To remove a tied environment variable from the environment, assign it the undefined value

undef $PATH; undef @LD_LIBRARY_PATH;

On VMS systems, arrays tied to environment variables are read-only. Attempting to change anything will cause a warning.

Chip Salzenberg </chip@fin.uucp/> and Gregor N. Purdy </gregor@focusresearch.com/>