Then end result is that, on the same search, ack is approximately 5 times faster than grep. I ran a few test cases myself and got similar results.
But the real reason I like it is the perl compatible regexes. The differences between perl regexes and gnu regexes are just big enough to be an annoyance.
In that particular case, ack's performance advantage seems to arise mostly because of a bug that causes GNU grep to be terribly slow in multibyte locales:
But, it's faster even when doing the same thing. For example, see the benchmark at http://blog.i-no.de/archives/2008/05/06/index.html.
Then end result is that, on the same search, ack is approximately 5 times faster than grep. I ran a few test cases myself and got similar results.
But the real reason I like it is the perl compatible regexes. The differences between perl regexes and gnu regexes are just big enough to be an annoyance.