AWK

AWK is a programming language designed for processing text-based data, either in files or data streams. It is an example of a programming language that extensively uses the string datatype, Associative Array-s (that is, arrays indexed by key strings), and regular expressions. AWK is one of the early tools to appear in Version 7 Unix and gained popularity as a way to add computational features to a UNIX pipeline.

http://en.wikipedia.org/wiki/AWK

http://gregable.com/2010/09/why-you-should-know-just-little-awk.html