regex, extract string NOT between two brackets

Question

OK regex question , how to extract a character NOT between two characters, in this case brackets.

I have a string such as: word1 | {word2 | word3 } | word 4

I only want to get the first and last 'pipe', not the second which is between brackets. I have tried a myriad of attempts with negative carats and negative groupings and can't seem to get it to work.

Basically I am using this regex in a JavaScript split function to split this into an array containing: "word1", "{word2 | word3}", "word4".

Any assistance would be greatly appreciated!

What language or tool are you using ? Can you show us some of what you have tried ? — Ibrahim Najjar, Oct 16 '13 at 21:31
@CarlNorum He means `word1` which is before the **vertical bar** `|` :) — Ibrahim Najjar, Oct 16 '13 at 21:32
sorry about that. I changed the word 'bar' to 'pipe' in the question above. thx. — shaun stewart, Oct 16 '13 at 22:04

Diver · Accepted Answer · 2022-12-06T19:56:28.947

39

Try using this pattern

/\|(?![^{]*})/g

with this text

word1 | {word2 | word3 } | word 4 | word 4 | {word2 | word3 }

This should match all of the Pipe symbols that are not inside {}.

*edit - removed link to dead site (Thanks Dennis)

edited Dec 06 '22 at 19:56

answered Oct 16 '13 at 22:26

Diver

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very helpful, specially for html strings that need some replacement in their nodes, but not in their attributes ;) – axel Nov 20 '18 at 13:34
refiddle.com doesn't link to the place you wanted it anymore – Dennis Hackethal Dec 04 '22 at 17:42

Andrew Cheong · Answer 2 · 2013-10-16T21:55:30.887

22

Depends on the language/implementation you're using, but...

\|(?![^{]*})

This matches a pipe that is not followed by a } except in the case that a { comes first.

The (?! ... ) is known as a negative lookahead assertion. This is easier to understand if we start with a positive lookahead assertion:

\|(?=[^{]*})

The above only matches a pipe that is followed by a } without encountering a { first. When you negate that by replacing the = with a !, the match is now only successful if there's no way for the positive case to be true (also known as the complement).

edited Oct 16 '13 at 21:55

answered Oct 16 '13 at 21:49

Andrew Cheong

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Why not just use a look ahead here? – hwnd Oct 16 '13 at 21:55
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@hwnd - Hm, perhaps it's possible, but I'm not seeing a way. Would you post what you're thinking? I'm curious! – Andrew Cheong Oct 16 '13 at 21:59
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Thanks for the explanation. So few of these are followed by explanations. – Chaim Eliyah Oct 11 '15 at 06:48

regex, extract string NOT between two brackets

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