Env(3) Perl Programmers Reference Guide Env(3)NAMEEnv - perl module that imports environment variables as
scalars or arrays
SYNOPSIS
use Env;
use Env qw(PATH HOME TERM);
use Env qw($SHELL @LD_LIBRARY_PATH);
DESCRIPTION
Perl maintains environment variables in a special hash
named "%ENV". For when this access method is inconve
nient, the Perl module "Env" allows environment variables
to be treated as scalar or array variables.
The "Env::import()" function ties environment variables
with suitable names to global Perl variables with the same
names. By default it ties all existing environment vari
ables ("keys %ENV") to scalars. If the "import" function
receives arguments, it takes them to be a list of vari
ables to tie; it's okay if they don't yet exist. The
scalar type prefix '$' is inferred for any element of this
list not prefixed by '$' or '@'. Arrays are implemented in
terms of "split" and "join", using "$Config::Con
fig{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 .= ":.";
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, '.';
is equivalent to:
use Envqw(PATH);
$PATH .= ":.";
except that if "$ENV{PATH}" started out empty, the second
approach leaves it with the (odd) value "":."", but the
first approach leaves it with ""."".
To remove a tied environment variable from the environ
ment, assign it the undefined value
undef $PATH;
undef @LD_LIBRARY_PATH;
LIMITATIONS
On VMS systems, arrays tied to environment variables are
read-only. Attempting to change anything will cause a
warning.
AUTHOR
Chip Salzenberg <chip@fin.uucp> and Gregor N. Purdy <gre_
gor@focusresearch.com>
2001-02-22 perl v5.6.1 Env(3)