Regex to match string 2 times but not 3

user_5789282 0
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I try to regex match string like these examples:

NetTAP IPX C-4-16

SmartTAP DP6409 Dual E1-11-16

but not these ones:

NetTAP IPX C-4-16-0

SmartTAP DP6409 Dual E1-11-16-0

SYSTEM

I've tried some solutions without success.

My idea was to search the -\d\d 2 times but not 3 times

(?!\-\d+)(\-\d+){2}$

or

[^(\-\d+)](\-\d+){2}$

Could you help me?

regex c#
2 Answers

You can use

(?<!-\d+)(?:-\d+){2}$

See the regex demo. Details:

  • (?<!-\d+) - a negative lookbehind that fails the match if there is a - char and one or more digits immediately to the left of the current location
  • (?:-\d+){2} - two repetitions of - and one or more digits
  • $ - end of string.
user_38329700

You can also match 3 times what you want to avoid, and capture 2 times what you want to keep using a capture group.

(?:-\d+){3}$|(-\d+-\d+)$

The pattern matches:

  • (?:-\d+){3}$ Match 3 repetitions at the end of the string
  • | Or
  • (-\d+-\d+)$ capture 2 repetitions at the end of the string in group 1

Regex demo

user_54249880
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