Linux Shell Scripting Cookbook - Third Edition

How it works...

Regular expressions are parsed by a complex state machine that tries to find the best match for a regular expression with a string of target text. That text can be the output of a pipe, a file, or even a string you type on the command line. If there are multiple ways to fulfill a regular expression, the engine will usually select the largest set of characters that match.

For example, given the string this is a test and a regular expression s.*s, the match will be s is a tes, not s is.

For more details on the regular expression components available, you can refer to http://www.linuxforu.com/2011/04/sed-explained-part-1/.