Issue
I need to match this for a substitute command:
whatever__MATCH_THIS__whateverwhatever__AND_THIS__whateverwhatever
I am trying with:
sed -e 's/__\(.*\)__/\{{\1}}/g' myfile
But this is eagerly matching __MATCH_THIS__whateverwhatever__AND_THIS__, producing:
whatever{{MATCH_THIS__whateverwhatever__AND_THIS}}whateverwhatever
But I wanted:
whatever{{MATCH_THIS}}whateverwhatever{{AND_THIS}}whateverwhatever
How can I specify a string to exclude, in the matching part? I know how to exclude one character (for example [^a]) but not how to exclude a string.
Solution
What you need is a non-greedy regex, but unfortunately sed doesn't allow that. However, it can be done in perl.
perl -pe 's|__(.*?)__|{{$1}}|g' <myfile
The question mark after the asterisk denotes the matcher as being non-greedy, so instead of taking the longest matching string it can find, it'll take the shortest.
Hope that helps.
If you wanted to put this in a perl script rather than run on the command line, then something like this will do the job:
#! /usr/bin/perl -w
use strict; # Habit of mine
use 5.0100; # So we can use 'say'
# Save the matching expression in a variable.
# qr// tells us it's a regex-like quote (http://perldoc.perl.org/functions/qr.html)
my $regex = qr/__(.*?)__/;
# Ordinarily, I'd write this in a way I consider to be less perl-y and more readable.
# What it's doing is reading from the filename supplied on STDIN and places the
# contents of the file in $_. Then it runs the substitution on the string, before
# printing out the result.
while (<>) {
$_ =~ s/$regex/{{$1}}/g;
say $_;
}
Usage is simple:
./regex myfile
whatever{{MATCH_THIS}}whateverwhatever{{AND_THIS}}whateverwhatever
It's Perl, there are a million and one ways to do it!
Answered By - chooban Answer Checked By - Robin (WPSolving Admin)