The article addresses this:

> The -F for grep indicates that we are only matching on fixed strings and not doing any fancy regex, and can offer a small speedup, which I did not notice in my testing.

I guess grep is probably clever enough to choose a faster matching algorithm once it's parsed the pattern and discovered it doesn't contain any regex fun.

In general grep seems smart enough that it would do that, but it hasn't been my experience. Just last week I was searching through a couple hundred gigs small xml files. I found that:

    $ LC_ALL=C fgrep -r STRING .

was much faster than plain grep. This was on a CentOS 5 box, so maybe newer versions of grep are smarter.

But then again, if I was on a newer box I'd just install and use ack or ag.

LC_ALL=C makes grep faster because text matching is normally locale-sensitive, for example 'S' ('\x53' in Big5) is not a substring of '兄' ('\xA5\x53' in Big5).