Regex - is it possible to find overlaping groups?

Question

I'm new to regex and just want to know if its possible to find "overlaping" groups in the matches.

assume the following string:

20122 0029431 7094 0111 5890

I want now all matches which are: 4number+space+4number+space+4number

What I tried is this: [0-9]{4}[\s][0-9]{4}[\s][0-9]{4}

But this just gave me: 9431 7094 0111

What I want are these matches:

9431 7094 0111
7094 0111 5890

is this possible with regex?

possible duplicate of [Overlapping matches in Regex](http://stackoverflow.com/questions/320448/overlapping-matches-in-regex) — Lazarus, Jul 04 '12 at 09:37

score 3 · Accepted Answer · answered Jul 04 '12 at 09:38

Yes, if you use lookahead assertions in combination with capturing groups:

Regex regexObj = new Regex(@"(?=(\d{4}\s\d{4}\s\d{4}))");
Match matchResult = regexObj.Match(subjectString);
while (matchResult.Success) {
    resultList.Add(matchResult.Groups[1].Value);
    matchResult = matchResult.NextMatch();
}

Regex - is it possible to find overlaping groups?

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