How to return value of a variable from shell script to perl script

babp has asked for the wisdom of the Perl Monks concerning the following question:

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Re: How to return value of a variable from shell script to perl script by ikegami (Patriarch) on Nov 11, 2009 at 19:25 UTC
Echo it and capture the script's STDOUT. my $output = `sh diff1.sh`; [download] See qx// in perlops	[reply] [d/l]
Re: How to return value of a variable from shell script to perl script by Plankton (Vicar) on Nov 11, 2009 at 19:41 UTC
I like using HEREDOC's like so ... my $shell_out = <<`SHELL`; diff $file1 $file2 ls -l SHELL print "$shell_out"; [download]	[reply] [d/l]
Re: How to return value of a variable from shell script to perl script by Perlbotics (Archbishop) on Nov 11, 2009 at 23:52 UTC
Welcome to the Monastery, babp. You might get better feedback if you format your question a little bit more readable. Please see Markup in the Monastery (esp. `<code>`). (Un-)fortunately, the HTML source of this page is more readable, so let me repeat the basic parts of your question: Perl program: `my $diff1 = system("sh diff.sh"); my $diff2 = system("sh diff1.sh");` [download] diff.sh: `a=diff aaa ccc` [download] diff1.sh: `b=diff aaa bbb` [download] The problem is, that `diff.sh` and `diff1.sh` don't do what you (probably) had in mind: The variable (a or b) is set to the string diff, then the shell tries to execute(!) aaa with argument bbb or ccc. Suggestion (non-Perl): Correct `diff.sh` (analogue `diff1.sh`), e.g. `diff aaa bbb a=$? # do something else with $a exit $a` [download] Which can be reduced to... `diff aaa bbb` [download] ... in case you only want to execute diff. The shell (usually) returns the exec state of the last statement executed. BTW: Perl has borrowed this idea here and there (e.g. return) - although this is not best practice. But then, wouldn't it be easier to avoid the `*.sh` wrappers and put that into the Perl script too? `my $diff1 = system("diff aaa ccc >/dev/null 2>&1"); my $diff2 = system("diff aaa bbb >/dev/null 2>&1");` [download] Note the redirections to get rid of diff's output. If your version of diff supports a switch to suppress output and just return the exec state, then give the system LIST variant a try for better security. Please be aware that `$diff1` and `$diff2` contain 0 on success but not necessarily 1 on error since catched signals are encoded into the return value (details in system). Finally, CPAN offers a lot of modules when searching for diff. Might be worth a check... HTH	[reply] [d/l] [select]
Re: How to return value of a variable from shell script to perl script by ikegami (Patriarch) on Nov 11, 2009 at 19:25 UTC
Echo it and capture the script's STDOUT. my $output = `sh diff1.sh`; [download] See qx// in perlops	[reply] [d/l]