grep: Magnificent Bastard

If you're ever playing around with BashPodder on Windows and you find yourself daunted by a single goddamn regex, try to keep this in mind:

grep is a magnificent bastard.

grep is a vital tool for any kind of data processing and a sysadmin's best friend. Naturally, Windows doesn't have it. grep uses regular expressions to find matching lines in a source file.

But grep has a dark secret. It's the -E flag, which the man page states will make grep "use extended regular expressions."

But wasn't grep using regular expressions before? Apparently not.

Broken:

EXTENSIONS="(mp3|torrent|ogg)"
if echo "$url" | grep "\.$EXTENSIONS$" > /dev/null

Works great:

EXTENSIONS="(mp3|torrent|ogg)"
if echo "$url" | grep -E "\.$EXTENSIONS$" > /dev/null