How can I exclude certain directories from bash commands like find, locate, cp, and such? For example, if I want to find and/or copy all .ogg files on my system that aren't already in my main music folder, how do I set up the commands to ignore that folder?

Where find is concerned, you can limit the part of the directory tree to search by specifying /, /etc, /home, /usr, etc in the find command. Locate uses regular expressions to search the locate database. I think you're SOL there. Cp may work if it's in a script, inside nested loops to compare directories, etc.
As far as your .ogg files are concerned, nested loops with an if-then-else-fi or case argument would work. The outer loop reads file names from one directory of interest; the inner loop reads file names from the other directory of interest; the if-then-else or case argument compares contents of the two directories, using bash variables such as -e (exists); !-e (doesn't exist); -a (and) and so on to make the filename comparison. The if-then-else or case arguments would then step through the options. If it exists here but doesn't exist there, copy from here to there. If it exists both places, skip to the next one, and so on.
A thorough (an I mean thourgh) reading of the bash man pages, or the Advanced bash-scripting guide, is in order. The loops I mentioned will require the use of square brackets to enclose arguments. In some cases, there MUST be a blank space between the brackets and the arguments enclosed by the brackets. If the blank space is omitted, the command won't work. Little things like that can make debugging scripts a nightmare.

Gah, that's too complicated. Besides, your suggestion for find wouldn't help me. I would want to search my whole profile starting at ~/, but exclude only the ~/music subtree, for example.

My .ogg example was only one example, though. For another, I have a folder /backups where I keep copies of important files that I don't want to show up on most searches. If I start a search from /, then the /backup folder is automatically included in the search, making it take more time than necessary and sometimes giving me duplicate matches.

All I really was hoping for was a fairly simple way to exclude a file or folder sub-tree from *any* major bash function. I was thinking that a regex might be the key, since most commands support them in some way. I tried playing around with expressions that would exclude certain strings while matching everything else, but I couldn't get anything to work. I just don't have enough knowledge of either bash or regex to do myself any good. I've only done a couple of easy scripts before too. I'm not ready yet for something that complicated.

I would think that it's possible. I can't imagine I'm the only person who's ever needed this kind of functionality.

updatedb --prunepaths='path1 path2...'
find -prune

Ummmm ....

That's very nice, but find doesn't make any use of locates
database for its searches, so it's a pretty useless combination.



To the OP ...



Cheers,
Tink

That's not generically possible, you can just filter out any output
you don't desire ... but that will vary with different commands, and
their different invocations. You still have the processing overhead
(searching/accessing the disks).


Cheers,
Tink