Regular expressions (regexps) are a very powerful tool, allowing you to look for text strings matching a particular pattern. In this first part of a two-part series, I'm going to look at using them on the command line. The next part will cover regexps in editors and other programs.
There's some basic regexp-type provision built into the shell: the most basic example of this is the * wildcard. This example will list every file in the current directory which has a .jpg extension: