Non-greedy match does not work

Question

I have a string like this

<tag1>
    <tag1>
        any text
    </tag1>
    text
</tag1>

and I want to find a <tag1>, that contains shortest text in this string.

I used the following regex <tag1>.*?</tag1>, but instead of <tag1>any text</tag1> i got <tag1> <tag1>any text</tag1>. Here is the example.

Why it doesn't works and what am I doing wrong?

Try `(.*)(.*?)` which matches the last inmost occurrence, but in general, it's not a good idea to use regular expressions for this purpose (they're not powerful enough to work with "bracketing") — Danstahr, Jan 14 '14 at 13:06
http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454 — Idan Arye, Jan 14 '14 at 13:10

Sujith PS · Answer 1 · 2014-01-14T13:42:48.343

1

You can use this simple code to solve your specific problem :

<tag1>[^<]*</tag1>

edited Jan 14 '14 at 13:42

answered Jan 14 '14 at 13:11

Sujith PS

4,606
3
30
61

What about `````` or escaped gt like `````` – NeplatnyUdaj Jan 14 '14 at 13:14
@NeplatnyUdaj 1. Hope it never happens. 2. Stop attempting with regex. In that order :) – Marko Topolnik Jan 14 '14 at 13:22

Vasili Syrakis · Answer 2 · 2014-01-14T13:11:44.347

0

I would be able to help you if those tags were not nested inside themselves (the same tag).

It is generally a bad idea to do this type of thing with regex. You should get a proper parser to fit your requirements.

edited Jan 14 '14 at 13:11

answered Jan 14 '14 at 13:05

Vasili Syrakis

8,846
1
36
55

score 0 · Accepted Answer · answered Jan 14 '14 at 13:16

It is not working, because it will start matching at the first <tag1> and then match as least as possible, so ending at the first </tag1>, resulting in "<tag1> <tag1>any text</tag1>".

You can avoid matching tags by using a negated character class

<tag1>[^<>]*</tag1>

See it on Regexr.

The other possibility is to use a negated lookahead assertion and match the next character only, if it is not the tag.

(<tag1>)((?!\1).)*?</tag1>

See it on Regexr

Non-greedy match does not work

3 Answers3