My system also doesn’t seem to know about RubyGems’ existence – unless I tell it to. The ‘require’ command gets overwritten by RubyGems so it can load gems, but unless you have RubyGems already required it has no idea how to do that. So if you’re writing your own, you can do:
require 'rubygems'
require 'gem-name-here'
If you’re running someone else’s code, you can do it on the command line with:
ruby -r rubygems script.rb
Also, there’s an environment variable Ruby uses to determine what it should load up on startup:
export RUBYOPT=rubygems
(from http://www.rubygems.org/read/chapter/3. The environment variable thing was pointed out to me by Orion Edwards)
(If “require ‘rubygems’ doesn’t work for you, however, this advice is of limited help 🙂