How do you use sed from Perl?

Question

I know how to use sed with grep, but within Perl the below fails. How can one get sed to work within a Perl program?

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Answer 1

It is easier to use Perl than to use grep and sed; see another answer.

Your code failed because Perl messed with the backslashes in your sed code. To prevent this, write your sed code in 'a single-quoted Perl string', then use \Q$sedCode\E to interpolate the code into the shell command. (About \Q...E, see perldoc -f quotemeta. Its usual purpose is to quote characters for regular expressions, but it also works with shell commands.)

my $fileToProcess = "example.txt";
my $sedCode = 's/^\([0-9]*\)[:].*/\1/p';
chomp(my @linenumbers =
      `grep -n "textToFind" \Q$fileToProcess\E | sed -n \Q$sedCode\E`);
printf "%s\n", join(', ', @linenumbers);

Given example.txt with

this has textToFind
this doesn't
textToFind again
textNotToFind

the output is 1, 3.