It's historical and sets your local character set. The default value on FreeBSD is POSIX which is an alias the historically value which is C. Desktop unix's like OSX or ubuntu set it to utf8.
Another note is that this is triggering fgrep which is already fast due to it's fixed length expression (i.e. no recursion is involved)
Another note is that this is triggering fgrep which is already fast due to it's fixed length expression (i.e. no recursion is involved)