Regex to match end of the string and capture the part before end of the string perl

Question

I'm trying to match any string with the regex that ends with /? and extract the string before /?

Below is my code:

$input = "boringinterestingboring/?";
if($input =~ /(.*)\/?$/) {
    print "$1\n";
}
else {
    print "not matched";
}

I'm trying to capture "boringinterestingboring" using (.*) but it's not doing that, instead it captures the whole string.

How should i get only the string before /?.

Please help.

You need to escape the `?` because it's a special character (quantifier that matches the preceding group 1 or 0 times). — CAustin, Jan 18 '19 at 22:33

score 2 · Answer 1 · edited Jan 20 '19 at 15:12

2

To match everything up to, but not including, a /?:

.*(?=/\?)

If you’re not sure about escaping, you can use a character class to do the escaping for you:

.*(?=/[?])

edited Jan 20 '19 at 15:12

haukex

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answered Jan 18 '19 at 22:54

Bohemian

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score 1 · Answer 2 · answered Jan 19 '19 at 04:18

It may seem duplicate, but as the answer of your question,
Your regex need to be:

/(.*)\/\?$/

or

/(.*)(?=\/\?$)/

Example:

$input = "boringinterestingboring/?";
print "Use \$1: $1\n" if($input =~ /(.*)\/\?$/);
print "Use \$1: $1\n" if($input =~ /(.*)(?=\/\?$)/);
print "Use \$&: $&\n" if($input =~ /.*(?=\/\?$)/);

Output:

Use $1: boringinterestingboring
Use $1: boringinterestingboring
Use $&: boringinterestingboring

Different ways, same destination. But either way, you should escape ? too, or put it in [].

stack0114106 · Answer 3 · 2019-01-19T11:17:21.097

Using positive lookahead. The assertion (?=..) will match /? but will not make it part of the capturing group even if it is nested in another group.

$ echo "boringinterestingboring/?" | perl -ne ' ($x)=/(boringinterestingboring(?=\/\?))/ ; print $x '
boringinterestingboring
$

Negative test case. Below prints nothing

$ echo "boringinterestingboring#?" | perl -ne ' ($x)=/(boringinterestingboring(?=\/\?))/ ; print $x '

$

Regex to match end of the string and capture the part before end of the string perl

3 Answers3