What is ack?
Ack is designed as a standalone (one perl file) replacement for 99% of the uses of grep. ack is intelligent about the files it searches. It knows about certain file types, based on both the extension on the file and, in some cases, the contents of the file.
Ack ignores backup files and files under CVS and .svn directories. It also highlights matches to help you see where the match was. Ack uses perl regular expressions (PCRE).
Designed for programmers with large heterogeneous trees of source code, ack is written purely in portable Perl 5 and takes advantage of the power of Perl's regular expressions.
Comments and Reviews
Said about ack as an alternative
SO much simpler. Sane, modern, defaults.