Getting a Grip on GNU grep (linux.com)

From TFA:

  grep '[[:punct:]]$' files

I suspect the author has grep aliased to `egrep` or `grep -E` because [:punct:] is an extended regular expression and GNU grep defaults to basic RE mode.

Before you invest time in grep, take a look at ack-grep http://betterthangrep.com/.

  ack-grep --thppt