OT-ish - converting hex output to binary on a Unix platform

Silly question, but maybe someone here's found a nice way of doing this using standard Unix tools... I have a few files in hex format (actually ROM dumps) and want to convert them to binary. Sort of the reverse of the hexdump utility. I'm not aware of a standard (and probably on-topic!) Unix util to do this, but maybe someone knows if there is one, or a handy way of doing this using some of the standard text-processing utils that Unix has... (files are in the format of 16 pairs of uppercase hex digits per line, with a trailing space after every pair - even the last one on a line) I'm rapidly coming to the conclusion that I need to remember some C again - and I've only just finished emptying my brain of it after the last time I needed to code in it a couple of months ago :-) cheers Jules