irb

Top top for using irb, the interactive ruby environment. Stick this in your ~/.bashrc or equivalent.

irb --readline -r irb/completion

And now you get nice completion of class and method names inside ruby. Lovely! Just like Python’s rlcompleter.

More info from Why’s Poignant Guide (which could use a few anchor’s).

As a side note, Ubuntu really needs to learn to install a few more Ruby packages by default. It’s missing webrick, yaml, irb, ri, erb and a lot of other stuff that should be standard in ruby 1.8. Grrr. Oh, it’s a bigger problem