Dovetailing with having multiple rubies, the reason why you have multiple rubies is to support older projects that depend on older rubies, and lock future projects to whatever was the best ruby for it at the time.
Or you're just developing libraries and are trying to be a good citizen of the ruby ecosystem - which includes that you'll try and support multiple interpreters and versions, if possible.
I agree. I don't just use RVM because my OS doesn't have the latest version.. I use RVM because I work on a project that uses jruby, and another that uses 2.1.1, and yet another that uses 2.0.0. Those projects may also require different versions of the same gem. With RVM I can have a .ruby-version and .ruby-gemset file in the projects root and RVM takes care of switching the version and gemset when I move into a projects directory. To quote the article: This seems like a much cleaner way of working!
This post hints at it, but you can install all of those Ruby versions on OpenBSD simultaneously. Ruby 1.8 has its binaries named "ruby18", "irb18", etc. and Ruby 1.9 is "ruby19", "irb19", etc. You can create a symlinks from "ruby" to "ruby19" and "irb" to "irb19" to set a system-wide default but any version can be used.
That still doesn't cover cases where you want to use multiple 1.9 versions, or if you want to test different patches, or if you want to use the latest version before your OS packages it. It's still the same basic problem as on Ubuntu.
Yes, and it's nothing new, you can do the same using Debian and then select the most appropriate version of ruby with update-alternatives... RVM and rbenv do something different, they allow you to _run_ different version of ruby for different apps. The fact that you can use them to set the default ruby for your system* is a quite handy side effect.
* And even then, you don't set the default ruby for the entire system, you set it for your own sessions.
