$ ruby -v ruby 2.0.0p247 (2013-06-27 revision 41674) [universal.x86_64-darwin13]
The -h flag will provide a list of all the command line options of Ruby.
$ ruby -h ...
Mostly we are going to create files in Ruby, but it is good to know that you can also create simple one-liners without creating a file.
$ ruby -e 'puts 19+23' 42