Env(3pm) Perl Programmers Reference Guide Env(3pm)
NAME
Env - perl module that imports environment variables as scalars or
arrays
SYNOPSIS
use Env;
use Env qw(PATH HOME TERM);
use Env qw($SHELL @LD_LIBRARY_PATH);
DESCRIPTION
Perl maintains environment variables in a special hash named %ENV. For
when this access method is inconvenient, the Perl module "Env" allows
environment variables to be treated as scalar or array variables.
The Env::import() function ties environment variables with suitable
names to global Perl variables with the same names. By default it ties
all existing environment variables ("keys %ENV") to scalars. If the
"import" function receives arguments, it takes them to be a list of
variables to tie; it's okay if they don't yet exist. The scalar type
prefix '$' 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;
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
<gregor@focusresearch.com>
perl v5.38.2 2023-11-28 Env(3pm)
perl 5.38.2 - Generated Thu Dec 5 13:39:30 CST 2024