The Basics of RVM
Wondering why you should use RVM? For a start, not only does RVM make installing multiple ruby interpreters / runtimes easy and consistent, it provides features such as gemsets that aren't typically supported out of the box on most ruby installs.
RVM also lets you use different rubies in a manner that wont mess with your existing ruby install (unless you tell it to) as well as letting you run multiple different rubies in seperate terminals concurrently!
Getting started
First, you must ensure that you install RVM .
Once that is done, you can open a new shell and start playing with rvm. To ensure rvm is loaded correctly, run:
∴ type rvm | head -n1
Assuming this shows "rvm is a function", you're good to go. As an example, to install and use Ruby 1.9.1 you may do:
∴ rvm install 1.9.1 ; rvm 1.9.1 ∴ ruby -v ruby 1.9.1p243 (2009-07-16 revision 24175) [x86_64-linux] ∴ which ruby /home/wayne/.rvm/ruby-1.9.1-p243/bin/ruby
Using any rubies not managed by rvm is easy as well - rvm refers to these as "system". That is to say, you can do:
∴ rvm system ∴ ruby -v ruby 1.8.7 (2008-08-11 patchlevel 72) [universal-darwin10.0] ∴ which ruby /usr/bin/ruby
Which tells the current shell to act as if you haven't run any "rvm use" commands yet.
For further explanation, look around the rest of the site. In particular, make sure you check out the workflow examples.
Remember that switching rubies is on a per-shell basis. If you want to set which ruby is available when you open a new shell, you'll need to set a default ruby interpreter.