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(Useful) Stupid Regex Tricks?

Posted by ScuttleMonkey on from the hope-you-like-reading-lots-of-random-characters dept.

careysb writes to mention that in the same vein as '*nix tricks' and 'VIM tricks', it would be nice to see one on regular expressions and the programs that use them. What amazingly cool tricks have people discovered with respect to regular expressions in everyday life as a developer or power user?"

8 of 516 comments (clear)

  1. Regexp-based address validation by mutende · · Score: 5, Informative

    Beautiful regexp that validates RFC 822 addresses: Mail-RFC822-Address.html

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  2. Re:IP and Hardware addresses by Richard_J_N · · Score: 5, Informative

    Of course, you can do better still. For mac addresses, try:
        ^([[:xdigit:]]{2}:){5}[[:xdigit:]]{2}$
    [:xdigit:] is short for hexadecimal digits, i.e. a-fA-F0-9
    We can also loop 5 times over the 'XX:' sections.

  3. Re:IP and Hardware addresses by Speare · · Score: 5, Informative

    For pretty much any useful stock problem solved by regular expressions, see Perl's Regex::Common module. A lot of these patterns are fiendishly complicated to deal with edge-cases properly.

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  4. One regex to match them all by gzipped_tar · · Score: 4, Informative

    This regex matches a number: interger or float, scientific notation or plain, plus or minus...

    [-+]?(?:\b[0-9]+(?:\.[0-9]*)?|\.[0-9]+\b)(?:[eE][-+]?[0-9]+\b)?

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  5. Do these questions really belong here? by DerCed · · Score: 5, Informative

    I wonder why such FAQs are still posted on a site like Slashdot. We now have a great repository for exactly this kind of questions:
    http://stackoverflow.com/questions/tagged?tagnames=regex&sort=votes&pagesize=15

  6. Re:Not a trick, but a question. by natebarney · · Score: 4, Informative

    Magic stuff like this is not working: /\([FB][ot]o\).*\1/ although that seems to be the closest description of what we wanted.

    In perl, I did /([FB][ot][o]).*\1/ and it seemed to work as you wanted. Also, if you're using a regex engine that supports lazy (non-greedy) quantifiers like perl does, I would use them in this case. It reduces backtracking. In perl, put a ? after the *.

  7. Re:IP and Hardware addresses by fbjon · · Score: 4, Informative

    It seems both Opera and ping in Windows interpret individual parts with leading zeros as octal. More interestingly, Opera also accepts hexadecimal. That makes constructing a regexp that validates any arbitrary IP address, and not just a valid dot-decimal, a bit more cumbersome.

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  8. Re:IP and Hardware addresses by tamyrlin · · Score: 4, Informative

    I personally like the regex-builder mode in Emacs as well. This one allows you to build a regexp while highlighting all matches in the current buffer.

    Of course, this should probably have been posted in the emacs thread earlier, but I think it is probably a good match for this thread as well :)

    To start it, just use M-x regexp-builder