What's the best way to find a string/regex match in files recursively? (UNIX)

Question

I have had to do this several times, usually when trying to find in what files a variable or a function is used.

I remember using xargs with grep in the past to do t

Answer 1

If you're looking for a string match, use

fgrep -r pattern .

which is faster than using grep. More about the subject here: http://www.mkssoftware.com/docs/man1/grep.1.asp

Answer 2

grep -r REGEX .

Replace . with whatever directory you want to search from.