Find all strings except one string using regex

Question

I want to match all strings except the string "ABC". Example:

 "A"     --> Match
 "F"     --> Match
 "AABC"  --> Match
 "ABCC"  --> Match
 "CBA"   --> Match
 "ABC"   --> No match

I tried with [^ABC], but it ignores "CBA" (and others).

I believe this has been discussed lengthily at http://stackoverflow.com/questions/406230/regular-expression-to-match-string-not-containing-a-word. — wombat, Apr 06 '13 at 15:57
@wombat, that other question is about rejecting a string that *contains* a certain substring. This one is about the special case of a string that consists entirely of `ABC`. `AABC` and `ABCC` are okay. — Alan Moore, Apr 06 '13 at 16:29

score 58 · Accepted Answer · answered Apr 06 '13 at 15:56

58

^(?!ABC$).*

matches all strings except ABC.

answered Apr 06 '13 at 15:56

Tim Pietzcker

1

I think he wants all combinations of 'A' 'B' 'C', right? (i.e. in any 3-length string) – d'alar'cop Apr 06 '13 at 15:57
1

@d'alar'cop `CBA` should be matched according to the examples – John Dvorak Apr 06 '13 at 15:58
but then shouldn't his [^ABC] work? if not, how come? – d'alar'cop Apr 06 '13 at 15:59
3

@d'alar'cop `[^ABC]` will reject `CBA` – John Dvorak Apr 06 '13 at 16:00
Ah, ok, I think I simply misunderstood your regex. '?!' is negative lookahead, right - what is the following '$'? (excuse my ignorance) – d'alar'cop Apr 06 '13 at 16:03
@d'alar'cop: It matches the end of the string. Otherwise, the regex would reject `ABCD`, too. – Tim Pietzcker Apr 06 '13 at 16:20
Ahh.. ich sehe jetzt. I didn't realise one could put the $ anchor inside in that way. Nett. Vielen Dank. – d'alar'cop Apr 06 '13 at 16:22
1

I also tried with negative but never get it works, because I didn't use an ending position inside. Thanks Tim! – PT Huynh Apr 07 '13 at 00:57
That's what I got: `var some = /^(?!ABC$).*/; 'ABC asdfas asdfasdf'.match(some) result: ["ABC asdfas asdfasdf"]` I think it should't include ABC here – RegarBoy Sep 29 '16 at 12:27
@developer: The author of the original question obviously thinks differently (see example number 4 and the comments under the question and Bohemian's answer). You seem to have misunderstood the question. – Tim Pietzcker Sep 29 '16 at 12:50

score 3 · Answer 2 · answered Apr 06 '13 at 16:36

3

Judging by you examples, I think you mean "all strings except those containing the word ABC".

Try this:

^(?!.*\bABC\b)

answered Apr 06 '13 at 16:36

Bohemian

1

@Bohemaian: No, I mean "all strings except this specific string 'ABC'" – PT Huynh Apr 07 '13 at 01:01

score 1 · Answer 3 · answered Apr 06 '13 at 16:54

1

Invert the Match with GNU Grep

You can simply invert the match using word boundaries and the specific string you want to reject. For example:

$ egrep --invert-match '\bABC\b' /tmp/corpus 
"A"     --> Match
"F"     --> Match
"AABC"  --> Match
"ABCC"  --> Match
"CBA"   --> Match

This works perfectly on your provided corpus. Your mileage may vary for other (or more complicated) use cases.

answered Apr 06 '13 at 16:54

Todd A. Jacobs

2

Your demonstration works perfectly, however I have no something like "invert-match" in my case. Thanks! – PT Huynh Apr 07 '13 at 01:40