Appendix A. Installing Ruby
Installing Ruby is a fairly trivial affair, but there are a few things worth paying attention to. You will want to use gems extensively, and not all installations include RubyGems by default. You may also want to use gems that take advantage of C extensions (for example, MySQL drivers and the Mongrel web server), which require that you have the proper development libraries and tools. In this appendix, we provide you with the simplest steps for installing a fully functional and up-to-date version of Ruby 1.8 on Windows, Mac OS X, and Linux.
Once Ruby is running, look at the A.4 section, where we provide useful tips for improving IRB (the Interactive Ruby Interpreter) and accessing documentation for all gems installed on your machine.
If you’re using Windows, you have three options. You can get the latest version of Ruby directly from the ruby-lang.org web site, with downloads for either Ruby 1.8 or 1.9. When you download the Ruby interpreter, it includes command-line tools like RDoc, IRB, and RI, but does not include RubyGems or many of the other libraries you need to get started.