Everyone familiar with RVM knows that it allows you to quickly and easily install a particular Ruby interpreter by simply running, for example,
rvm install rbx
What is not widely known (yet) is that there is a "Named Rubies" feature that allows you to install altered versions of the same Ruby installation along side the original.
In the case of Rubinius there is this facinating branch called 'hydra'. So let us see how we can have the Rubinius master branch installed as the main rbx with the hydra branch installed along side as well.
As above you first install rbx which is currently defaulted to -head version so
rvm install rbx
is currently equivalent to
rvm install rbx-head
After we have the mainline head Rubinus branch installed, we now want to use the named rubies feature. This is done using the -n specifier in the Ruby identifier string. So for example to install our hydra branch as an RVM ruby with the name 'hydra' in it we do the following:
rvm install --branch hydra rbx-nhydra
Now we can see that they can be used together! Using the Rubinius master environment,
$ rvm rbx ; ruby -v rubinius 1.2.1 (1.8.7 6feb585f 2011-02-15 JI) [x86_64-apple-darwin10.6.0]
Whereas using the Rubinius hydra environment,
$ rvm rbx-nhydra ; ruby -v rubinius 1.3.0dev (1.8.7 6feb585f xxxx-xx-xx JI) [x86_64-apple-darwin10.6.0]
We see that the next release of Rubinius (hydra branch) is indeed version 1.3.0 whereas the master branch is version 1.2.1.
Also please note that RVM creates wrapper scripts, so you do not need to switch out the entire environment just to run the differen versions either:
For Rubinius master,
$ rbx-head -v rubinius 1.2.1 (1.8.7 6feb585f 2011-02-15 JI) [x86_64-apple-darwin10.6.0]
For Rubinius hydra,
$ rbx-head-nhydra -v rubinius 1.3.0dev (1.8.7 6feb585f xxxx-xx-xx JI) [x86_64-apple-darwin10.6.0]
There is a lot more available to you than this, for more information on RVM capabilities please visit the RVM Website and also come talk to us in #rvm on irc.freenode.net during the daytime EDT.
I hope that this is helpful and informative to you!