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

This is one of the cases for which I've started using ack (http://petdance.com/ack/) in lieu of grep. From the site, you can get instructions to install it as a Perl CPAN component, or you can get a self-contained version that can be installed without dealing with dependencies.

Besides the fact that it defaults to recursive searching, it allows you to use Perl-strength regular expressions, use regex's to choose files to search, etc. It has an impressive list of options. I recommend visiting the site and checking it out. I've found it extremely easy to use, and there are tips for integrating it with vi(m), emacs, and even TextMate if you use that.