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

I suggest changing the answer to:

grep REGEX -r .

The -r switch doesn't indicate regular expression. It tells grep to recurse into the directory provided.