Agrep

Agrep (Approximate grep) is a fuzzy string searching program, developed by Udi Manber and Sun Wu between 1988 and 1991, for use with the Unix operating system. It was later ported to OS/2, DOS, and Windows.

It selects the best-suited algorithm for the current query from a bunch of the known fastest (built-in) string searching algorithms.

Agrep is also the search engine in the indexer program GLIMPSE. It is free for private and non-commercial use only, and belongs to the University of Arizona.

There is also another implementation of agrep as a part of the TRE regexp matching package. It is licensed under the GPL.