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.

Answer 1

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

Answer 2

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.

Answer 3

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

This should work for your case.

Answer 4

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)$/))`