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, Jan 14 '20 at 13:19
https://stackoverflow.com/questions/1780483/lines-and-columns-environmental-variables-lost-in-a-script — martin clayton, Jan 14 '20 at 13:20
@w.k : `LINES=20 my_script.pl` is equivalent to `(export LINES=20; my_script.pl)`. You can't see non-exported variables. — user1934428, Jan 14 '20 at 14:12

score 4 · Accepted Answer · answered Jan 14 '20 at 13:35

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).

How could I access shell variable from Perl script?

1 Answers1