(Useful) Stupid Regex Tricks?

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?"

Comments

IP and Hardware addresses

[rallymatte]

To filter a string to make sure it's a valid ip address this regexp is quite useful.
/^((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])$/

And this one for mac addresses
/^[0-9a-fA-F]{2}:[0-9a-fA-F]{2}:[0-9a-fA-F]{2}:[0-9a-fA-F]{2}:[0-9a-fA-F]{2}:[0-9a-fA-F]{2}$/

use Regex::Common;

[oneiros27]

use Regex::Common qw(URI net);
$text_with_urls =~ m/$RE{URI}/;
$text_with_ips =~ m/$RE{net}{IPv4}/;

Re:99 Bottles of Beer on the wall

[Culture20]

(I would quote the final result but /. won't allow that many "junk" characters.. let's hope that doesn't cripple this entire discussion.)

Interesting that a site for nerds doesn't allow a lot of characters commonly used in source code.

Re:Regexp-based address validation

[xenocide2]

The regex is beautiful in the sense that it lets you not be one of those assholes who refuses valid email addresses.

Opposite

[Christopher_Olah]

IMHO, this is exactly the way that Slashdot should be going. Threads like this are interesting, add to the reservoirs of internet knowledge, and have the highest quality to noise ratios.

I (and I suspect many others) read Slashdot not for the latest +5 funny comment (though those can be fun to read) but to read the opinions of brilliant minds. And when those minds start trading secrets... Everyone wins.