RegEx match if present

Asked 2011-10-08T12:19:45.100

Is there something in regex to match (conditionally) only if it exists ?

e.g.

the string maybe

question_1

or only

question

In case of the former, it should match the integer in the end, but as in the case of the latter, it should leave it.

regex

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3 Answers

Don't quite understand the question. Do you just want to extract the number?

question_(\d+)

answered 2011-10-08T12:26:05.487

in perl you could do something like:

my $string = 'question_1';
my $question_number = $string =~ /question_(\d+)/i;

now $question_number will hold the int if it matches and will be undef if it doesn't

answered 2011-10-08T12:25:48.890

If the underscore and the number are optional try something like this:

question(?:_\d)?

answered 2011-10-08T12:27:22.603