hmm....haven't done ever (as finding all the files on one's disk takes a hell of a long time

heheh) but here's some starting things:
"cat" prints out the contents of a file, like "cat foo.txt" prints what's inside foo.txt and "cat /*/*" might then print out everything in everywhere? not sure.
"grep" cuts off and prints only the parts that are given, for example "cat foo.txt | grep you" would first read through file foo.txt, then print out every line which has the string "you" inside it (like you, you're, yours, fdsajlkfdsyoufdlask and so on)
I don't know any ready program...perhaps there is, perhaps not. You might want to try combining different commands to success....