Can grep show only words that match search pattern?

Question

Is there a way to make grep output \"words\" from files that match the search expression?

If I want to find all the instances of, say, \"th\" in a number of files, I

Answer 1

You could pipe your grep output into Perl like this:

grep "th" * | perl -n -e'while(/(\w*th\w*)/g) {print "$1\n"}'