I gave a lightning talk about using the ruby program the other day at Eindhoven.rb, the Ruby user group for the Eindhoven area.
Ruby is a programming language, and
ruby is the program you invoke it with. It takes some interesting arguments that enable you to use it as a general-purpose command line scripting solution – traditionally the domain of Perl.
In my slides I go over most of the options and some common use cases, so flip through them. Being a lightning talk, there wasn’t time to review these features in-depth, but Programming Ruby 1.9 is a great reference book to find out more.