nawk

Brian Kernighan's pattern scanning and processing language

Awk scans input files for specified patterns and can perform an associated action when a line of the file matches the pattern. This is the One True version of awk described in "The AWK Programming Language" by Al Aho, Brian Kernighan, and Peter Weinberger (Addison-Wesley, 1988, ISBN 0-201-07981-X).