Xmodulo posted a tutorial about searching text files

For a system admin or a programmer, grep and the likes are probably the most popular tools when it comes to searching through complex configuration directories and large trees of source code for a particular text string or pattern.

If grep is one of your favorite tools, chances are that you will like ack even better. ack is a Perl-based command-line utility similar to grep, but designed to improve the search speed and capabilities of grep. Especially if you are a programmer, I strongly recommend replacing grep with ack. The usage of ack is heavily optimized for code search, so a programmer like you can perform complex search on source code trees with fewer keystrokes.

  How to search text files for patterns efficiently