Installing Ruby on Rails used the manual method rather than the scripts on offer as the scripts point to unsupported versions of Ruby:
http://blog.sudobits.com/2012/05/02/how-to-install-ruby-on-rails-in-ubuntu-12-04-lts/

This has a useful command list & runtime instructions also:
http://tutorialsave.com/how-to-run-ruby-on-rails-on-a-mac/