getopt manpage

[waider]

if the option string is four chars long, and it's tuesday, and raining, and you're on a POSIX system, but the POSIXLY_CORRECT environment variable isn't set, and your name begins with a vowel, then getopt will set some random variables, return the last number you thought of, and carry the one.

Ok, it's not quite that bad, but it's close.