Elegant way to set an environment variable in Perl

user_9808098 0
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In my Perl script, I'm trying to set an environment variable (for example PATH). In case it's already defined, add the path to it. Otherwise, set the env. The code:

if (defined($ENV{"PATH"})) {
    $ENV{"PATH"} = $ENV{"PATH"}.":/usr/pkgs/";
} else {
    $ENV{"PATH"} = "/usr/pkgs/";
}

Is there a better and elegant way to do this in Perl? Maybe a one liner? Note that the env does not have to be PATH.

perl environment-variables
4 Answers

If you use the Env Core module:

use warnings;
use strict;
use Env qw(@PATH);

push @PATH, '/usr/pkgs/';
user_1977580

I'd probably write something like this, where I use the length to determine what to add on (although I don't expect "0" to ever be the value of $ENV{PATH}). The Config module knows what the path separator should be:

use Config qw(%Config);

$ENV{PATH} .= ( length $ENV{PATH} ? $Config{path_sep} : '' ) . "/usr/pkgs/";
brian_d_foy_27661760

Based on Mathias' answer, which basically uses split as a hack to create an empty list for empty values in $ENV{PATH}. You can use the simpler check || which checks if the value in the variable is false, which in a Perl scalar means basically empty string, undefined or zero. Since we want to avoid the possibility of adding a colon to the start of the string, we want to replace it with the empty list (). So it becomes:

$ENV{PATH} = join ":", $ENV{PATH} || (), "/usr/pkgs/";

Technically, 0 could be a valid path, but it feels unlikely to be a correct path.

user_7254180

I would use split and join like this:

$ENV{PATH} = join(":", split(/:/, $ENV{PATH}), "/usr/pkgs")
user_56722450
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