How could I access shell variable from Perl script?

Question

In the terminal, I can access variable $LINES:

$ echo $LINES
39

Running Perl script like so:

 #!/usr/bin/env perl

 use strict; use warnings;

 my $cmd = q|echo $LINES|;
 my $lines = `$cmd`;

 print "lines: $lines\n";

gives output: lines:. I tried also accessing %ENV, but it does not contain this particular key.

How could I access shell variable $LINES from a Perl script?

No, but it should work, cause I tried LINES=20 my_script.pl and it works — w.k
– w.k, Commented Jan 14, 2020 at 13:19
@w.k : LINES=20 my_script.pl is equivalent to (export LINES=20; my_script.pl). You can't see non-exported variables. — user1934428
– user1934428, Commented Jan 14, 2020 at 14:12

Håkon Hægland · Accepted Answer · 2020-01-14 13:35:55Z

4

From bash manual:

When a program is invoked it is given an array of strings called the environment. [...] The shell provides several ways to manipulate the environment. On invocation, the shell scans its own environment and creates a parameter for each name found, automatically marking it for export to child processes. Executed commands inherit the environment. The export and declare -x commands allow parameters and functions to be added to and deleted from the environment.

So (assuming a Bash shell) using:

export LINES

will make the variable $LINES available from within a Perl script startet from the Shell (using $ENV{LINES} from the Perl script).

answered Jan 14, 2020 at 13:35

Håkon Hægland

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