Perl Regex: Negative lookaheads

user_388325 0
Viewed 451

I have this test text:

cake/app/webroot/js/compiled/shop.js
cake/app/webroot/js/compiled/shop.min.js
cake/app/webroot/js/good/thing.js

When I try this:

/^(?!.*compiled)(?!.*min).*$/

It doesn't match anything. But when I add:

/^.*

to the beginning, it matches something on each line. (I only want the last line matched.)

What am I missing?

negative-lookahead perl regex
1 Answers

Your first regex matches the third line

my $re = qr/^(?!.*compiled)(?!.*min).*$/;
while(<DATA>) {
    chomp;
    if (/$re/) {
        say 'OK : ', $_;
    } else {
        say 'KO';
    }
}


__DATA__
cake/app/webroot/js/compiled/shop.js
cake/app/webroot/js/compiled/shop.min.js
cake/app/webroot/js/good/thing.js

Output: 

KO
KO
OK : cake/app/webroot/js/good/thing.js

When you add .* at the beginning, it matches the whole line then the negative lookahead is true, there is no compiled or min after the regex has consume all the characters, so the match is true.

user_3722390
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