The --exclude option for recursive commands

This is one of those "I thought everyone knew about this." tips. I recently discovered that quite a few people don't know that quite a few GNU/*nix commands that operate recursively have an --exclude option so you can skip certain directories.

The conversation came up when talking about ctags - but here are some other commands that have the same:

• diff
• rsync
• tar
• grep
• du

So, man <the_command> and look for --exclude. Many of these programs will also have either an --exclude-from or allow you to supply an @ prefixed filename to the --exclude option so you can give a file that contains a list of dirs/paths to exclude.

Watch the specifics of each command, some are quite exotic (especially rsync), and some have other related options (like grep has --exclude-dir)