Probably everyone that use a terminal know the command
grep, from its man page:
grep searches the named input FILEs (or standard input if no files are named, or if a single hyphen-minus (-) is given as file name) for lines containing a match to the given PATTERN. By default, grep prints the matching lines.
So this is the best tool to search in big file for a specific pattern, or a specific process in the complete list of running processes, but it has a small limit, it searches for the exact string that you ask, and sometime it could be useful to do an “approximate” or “fuzzy” search.
For this goal the program agrep was firstly developed, from wikipedia we can see some detail of this software:
agrep (approximate grep) is a proprietary approximate string matching 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 variety of the known fastest (built-in) string searching algorithms, including Manber and Wu’s bitap algorithm based on Levenshtein distances.
agrep is also the search engine in the indexer program GLIMPSE. agrep is free for private and non-commercial use only, and belongs to the University of Arizona.
So it’s closed source, but luckily there is an open source source alternative: tre-agrep