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Is it possible to define a regex which will match every character except a certain defined character or set of characters?

Basically, I wanted to split a string by either comma (,) or semi-colon (;). So I was thinking of doing it with a regex which would match everything until it encountered a comma or a semi-colon.

Jonathan Leffler
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KJ Saxena
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4 Answers4

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[^,;]+

You haven't specified the regex implementation you are using. Most of them have a Split method that takes delimiters and split by them. You might want to use that one with a "normal" (without ^) character class:

[,;]+
Mehrdad Afshari
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    And the question doesn't specify whether adjacent separators are allowed, so the trailing '+' is slightly dubious. – Jonathan Leffler Sep 11 '09 at 06:26
  • Getting an error only for semicolon-- unterminated regexp meets end of file – Jaswinder Dec 21 '17 at 03:07
  • I had a similar requirement where I want to avoid semicolon and comma at the end I tried a lot but no success below is the Regex I am using const regexDomain = /^(?:[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?\.)+[A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9]/g; Well it validates if I use , and ; in between but fails at the end to vliadate. – Harry Sep 04 '18 at 15:01
106

Use character classes. A character class beginning with caret will match anything not in the class.

[^,;]
Thom Smith
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    More about [negated character classes](http://www.regular-expressions.info/charclass.html) – HEX Oct 17 '15 at 21:09
  • I had a similar requirement where I want to avoid semicolon and comma at the end I tried a lot but no success below is the Regex I am using const regexDomain = /^(?:[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?\.)+[A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9]/g; Well it validates if I use , and ; in between but fails at the end to vliadate. – Harry Sep 04 '18 at 14:55
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Use a negative character class:

[^,;]+

This will match at least one character that is not a comma nor a semicolon. If there are multiple characters matching this criterion, all of them will be matched (+ at-least-once quantifier)

knittl
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2

Use this:

([^,;]*[,;])*
NawaMan
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    That requires the comma or semi-colon as a field delimiter, rather than as a field separator. The difference matters at the end of a 'line' (or other scanned record structure); typically, you don't want to insist on a comma or semi-colon after the last field. If your regex engine is powerful enough, you can use '`(?:([^,;]*)(?:[^,;]|$))`' (PCRE with non-capturing parentheses). The alternatives of a comma or semi-colon after the field, or end of record, makes things work better. Also consider whether empty fields are allowed. – Jonathan Leffler Sep 11 '09 at 06:24
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    Finally, you have to worry about what is actually returned by the captures - did you really want the separators included, and if there are 10 fields on a line, how many of them are returned by the capture notation. – Jonathan Leffler Sep 11 '09 at 06:25
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    You are right about all that but the reason I didn't concert those thing in my answer is that I do not know what language/library of RegEx the questioner is asking. He may be using "GREP". Anyway, I appreciate you adding those comments to clear things up for him. :D – NawaMan Sep 11 '09 at 16:48