These instructions allow you to install Ruby 1.9 on Ubuntu 13.04.
Install the required libraries. From the terminal type:
sudo apt-get install ruby-dev ruby-sqlite3 ruby-sinatra ri1.9
Verify that Ruby was installed correctly. Type at the terminal:
ruby -v
The output should be:
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux]
To run the Interactive Ruby Shell (IRB) type at the terminal:
irb
Press Ctrl+D to exit.