Tim McIntire has published a 3rd article in UNIX tips and tricks for a new user series - Introducing filters and regular expressions Using grep, sed, and awk:
Discover the power of UNIX filters. In this tutorial, you'll learn about the grep family in depth, including the syntax of regular expressions in many UNIX utilities. You'll also find out more about the stream editor, sed, as well as examine the awk pattern scanning language through examples and explanations.
In this tutorial
=> Regular expressions
=> Searching files with grep
=> Editing files with sed
=> Using awk on the command line
Read more at IBM developerworks... (free registration required to access tutorial)