pcre regex match nth occurence

Question

This is not a duplicate. I have checked before asking.

I have this string separated with | and I want to match the nth element.

aaaaaaaaa aaa|bb bbbbb|cccc ccccccc|ddd ddddddd|aaa aaa aaaaa|zzz zzz zzzzzzz

The closer I got is using this pattern but it buggy:

([^\|]*\|){2}[^\|]*

https://regex101.com/r/EYZbK5/1

This is plain pcre. In this context, javascript such .split() cannot be used.

Say I want to get the 3rd element cccc ccccccc what regex should I use?

This seems to be an exact duplicate. Please see the marked question and if it didn't provide you an answer then edit accordingly. — revo, Sep 20 '18 at 18:30
Well, the accepted answer really suggests using a capturing group. Since the answer accepted suggest the same solution, it is really a dupe, as you are not interested in PCRE specific options. — Wiktor Stribiżew, Sep 21 '18 at 08:21

score 4 · Answer 1 · answered Sep 20 '18 at 17:43

You may use

^(?:[^|]*\|){2}\K[^|]*

See the regex demo.

Details

^ - start of string
(?:[^|]*\|){2} - a non-capturing group matching two consecutive occurrences of
- [^|]* - a negated character class matching 0+ chars other than |
- \| - a | char
\K - match reset operator that discards the text matched so far
[^|]* - 0+ chars other than |.

To avoid empty string matches, you may replace the last [^|]* with [^|]+.

The fourth bird · Accepted Answer · 2018-09-20T17:49:02.463

You could use an anchor to assert the start of the line and then repeat not matching a | followed by a | 2 times. Then capture the third part in a capturing group which will contain cccc ccccccc

^(?:[^|]*\|){2}([^|]*)

Regex demo

Explanation

^ Assert the start of the line
(?: Start non capturing group
- [^|]*\| Match not a | using a negated character class zero or more times followed by a |.
){2} close non capturing group and repeat that 2 times
([^|]*) Capture in a group matching not a | zero or more times

The Scientific Method · Answer 3 · 2018-09-20T18:11:45.230

2

you may try this and take group2

(\|?(.*?)(?:\|)){3}

demo and explanation

edited Sep 20 '18 at 18:11

answered Sep 20 '18 at 17:48

The Scientific Method

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This matches `cccc ccccccc|` including the `|` – The fourth bird Sep 20 '18 at 17:54
also it doesn't get the last '`zzz zzz zzzzzzz`' – Azevedo Sep 20 '18 at 18:03
oh sorry, updated and he can take group2 – The Scientific Method Sep 20 '18 at 18:12

pcre regex match nth occurence

3 Answers3