Regex: match pattern but not certain word

Question

Is there a possibility to write a regex that matches for [a-zA-Z]{2,4} but not for the word test? Or do i need to filter this in several steps?

A tip: always specify which language and regex engine you're using; they're often different. — ruakh
– ruakh, Commented Sep 13, 2012 at 12:39
if you plan to replace every 2-4 character word in a string, you should mention that too, because depending on the solution parts of "test" could match too. but then there are other solutions more helpful — Hachi
– Hachi, Commented Sep 13, 2012 at 12:48
no its just for matching a string like this: foobar.aaa.dsf but there are strings like foobar.test.dsf i dont want to match. so its not about replacing something or so. — reox
– reox, Commented Sep 14, 2012 at 8:53

Wiseguy · Accepted Answer · 2012-09-13 12:38:29Z

17

Sure, you can use a negative lookahead.

(?!test)[a-zA-Z]{2,4}

I don't know if you'll need it for what you're doing, but note that you may need to use start and end anchors (^ and $) if you're checking that an entire input matches that pattern. Otherwise, it could match something like ouaeghAEtest because it will still find four chars somewhere that aren't "test".

answered Sep 13, 2012 at 12:38

Wiseguy

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2 Comments

shrx Over a year ago

Also, for multiple word exclusions: (?![test1,test2])[a-zA-Z]{2,4}

Wiseguy Over a year ago

@shrx Not quite. You've used a character class, so the lookahead will only match against the first character if it is one of those listed. (diagram) So it will reject any word that begins with a t, e, s, 1, ,, or 2. Use the pipe "or" operator instead: (?!test|foo|bar)[a-zA-Z]{2,4} (diagram)

Julius Vainora · Accepted Answer · 2012-09-13 12:40:28Z

-1

[A-Za-su-z][A-Za-df-z]{0,1}[A-Za-rt-z]{0,1}[A-Za-su-z]{0,1}

just a idea, haven't use real code to try

edited Sep 13, 2012 at 12:40

Julius Vainora

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answered Sep 13, 2012 at 12:39

倪玉哲

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