Regex: Match a pattern but exclude one case

Question

I want to include all strings starting from a to m. This can be done using [a-m]* regex but I don't want a case where the string starts with "deal_string". What is the regular expression for this?

Test cases:

assets/filename.ext           -> pass
deal_string/filename.ext      -> fail
deal_string.ext               -> fail
deal_string_1.ext             -> fail
deal_draft.txt                -> pass
assets_deal_string.txt        -> pass
bombay.txt                    -> pass
zombie.srt                    -> fail
some_deal_string.txt          -> fail
zobie_special_string.txt      -> fail

If you want to include all strings that start from `a` to `m` then how is it that all of the other cases pass? The only ones that should pass excluding `special_string` is `assets/filename.ext` and `bombay.txt` — hwnd, Jul 15 '14 at 15:03

hwnd · Accepted Answer · 2014-07-15T17:41:20.147

5

Use a Negative Lookahead here. If you want to match all strings that begin with a through m excluding the strings that begin with "deal_string", you can use:.

^(?!deal_string)[a-m].*$

Live Demo

edited Jul 15 '14 at 17:41

answered Jul 15 '14 at 15:11

hwnd

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Regex: Match a pattern but exclude one case

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