regex to remove ordinals

Question

I need to remove ordinals via regex, but my regex skills are quite lacking. The following locates the ordinals, but includes the digit just prior in the return value. I need to isolate and remove just the ordinal.

[0-9](?:st|nd|rd|th)

Answer 1

You need to use a look-behind assertion so that only st|nd|rd|th preceded by a [0-9] are matched, but the [0-9] isn't included in the match. i.e.:

(?<=[0-9])(?:st|nd|rd|th)

I've linked to the perl-compatible syntax, but if you're using posix, posix extended, vi or one of many other regex syntaxes you'll need to look up the syntax.