regexp inverse mac-address match

Question

I wrote this perl regex in order to get all mac-addresses:

^(?([0-9A-Fa-f]{12}))$

This works fine, but the inverse match (all string without mac-address) doesn't works:

^(?!([0-9A-Fa-f]{12}))$

what is the best way to write this regex?

Should anyone have forgotten, a MAC address is usually something like `A1-B2-32-DD-5F-FF`, or in the OPs case, probably `A2B232DD5FFF`. — h2ooooooo, Jun 12 '13 at 09:29
you're right, but in my case the mac-address does not have special characters — Vincenzo, Jun 12 '13 at 09:31
Provide some sample input that you're trying to match or not match. — anubhava, Jun 12 '13 at 09:33
related: [Regular expression to match string not containing a word?](http://stackoverflow.com/q/406230/4279) — jfs, Jun 12 '13 at 09:43
@anubhava: I want to match this string: "23af23af23ca", but i do not want match this string: "realm\username" — Vincenzo, Jun 12 '13 at 09:46

stema · Accepted Answer · 2013-06-12T09:52:47.507

1

With your original pattern you are starting a conditional (the (?(...) part), but without then/else clause. I am quite sure you didn't want this.

Your second pattern has the problem, that you are checking a condition with your negated lookahead, but you don't match something. So change it to

^(?![0-9A-Fa-f]{12}$).*$

This will match any pattern that is not [0-9A-Fa-f]{12}.

edited Jun 12 '13 at 09:52

answered Jun 12 '13 at 09:47

stema

1 Answers1