How to match all strings other than a particular one

Question

To match all characters except vowels, we can use [^aeiou].

I wonder

• how to match all strings other than a particular one? For example, I want to match a string which is not dog. So cat, sky, and mike will all be matches.

• how to match all strings other than a few strings, or other than a regular expression? For example, I want to match a string which is not c.t. So sky and mike will all be matches, but cat and cut will not be matches.

Thanks.

Answer 1

1. How to match all strings other than a particular one

^(?!your_string$).*$

2. How to match all strings other than a few strings

^(?!(?:string1|string2|string3)$).*$

How does that work?

1. The idea is to use a negative lookahead (?! to check that the string does not consists solely of the string(s) to avoid. If the negative lookahead (which is an assertion) succeeds, the .*$ matches everything to the end of the string.
2. Note the use of the ^ anchor at the beginning to ensure we are positioned at the beginning of the string.
3. Note the $ anchor inside the negative lookahead to ensure that we are excluding your_string if it is indeed the whole string, but that we do not exclude your_string and more

Reference

1. Mastering Lookahead and Lookbehind
2. Negative Lookaheads