What's a regex that matches all numbers except 1, 2 and 25?

Question

There's an input of strings that are composed of only digits, i.e., integer numbers. How can I write a regular expression that will accept all the numbers except numbers 1, 2 and 25?

I want to use this inside the record identification of BeanIO (which supports regular expressions) to skip some records that have specific values.

I reach this point ^(1|2|25)$, but I wanted the opposite of what this matches.

first what language are you using? and second how about sharing what you have tried so far? — Dalorzo, Aug 28 '14 at 16:17
Why are you so intent on using a regex for this? It sounds like you should just do `atoi()` or similar and compare the actual numbers, or even just compare strings directly. — Dolda2000, Aug 28 '14 at 16:18
Actually regex won't match `numbers` it only matches characters. A seven digit character string will still be just an int. — , Aug 28 '14 at 16:46
Does your script/language support negative constructs? `if ( matched ) then fail` — , Aug 28 '14 at 16:50

score 25 · Accepted Answer · edited Aug 28 '14 at 17:11

25

Not that a regex is the best tool for this, but if you insist...

Use a negative lookahead:

/^(?!(?:1|2|25)$)\d+/

See it here in action: http://regexr.com/39df2

edited Aug 28 '14 at 17:11

Keith Thompson

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answered Aug 28 '14 at 16:19

Joseph Silber

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then do us a favor and share what would be, to your eye, better/best tool for the task ;) – ash17 Jun 24 '23 at 10:22

score 3 · Answer 2 · edited Oct 12 '20 at 15:28

3

You could use a pattern like this:

^([03-9]\d*|1\d+|2[0-46-9]\d*|25\d+)$

Or if your regex engine supports it, you could just use a negative lookahead assertion ((?!…)) like this:

^(?!1$|25?$)\d+$

However, you'd probably be better off simply parsing the number in code and ensuring that it doesn't equal one of the prohibited values.

edited Oct 12 '20 at 15:28

informatik01

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answered Aug 28 '14 at 16:20

p.s.w.g

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score 1 · Answer 3 · answered Aug 28 '14 at 16:38

1

  (?!^1$|^2$|^25$)(^\d+$)

This should work for your case.

answered Aug 28 '14 at 16:38

vks

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score 0 · Answer 4 · edited Apr 17 '22 at 18:42

See this related question on Stack Overflow.

You shouldn't try to write such a regular expression since most languages don't support the complement of regular expressions.

Instead you should write a regex that matches only those three things: ^(1|2|25)$ - and then in your code you should check to see if this regex matches \d+ and fails to match this other one, e.g.:

`if($myStr =~ m/\d+/ && !($myStr =~ m/^(1|2|25)$/))`

What's a regex that matches all numbers except 1, 2 and 25?

4 Answers4