How do RVM and rbenv actually work?

Question

I am interested in how RVM and rbenv actually work.

Obviously they swap between different versions of Ruby and gemsets, but how is this achieved? I had assumed they

Answer 1

rvm system
env > before
rvm jruby # or whatever
env > after
diff after before

Gives you approximately:

< GEM_HOME=$HOME/.gem/ruby/1.9.1
---
> GEM_HOME=$HOME/.rvm/gems/jruby-1.6.6
< GEM_PATH=$HOME/.gem/ruby/1.9.1
---
> GEM_PATH=$HOME/.rvm/gems/jruby-1.6.6:$HOME/.rvm/gems/jruby-1.6.6@global
*bunch of rvm_*
> MY_RUBY_HOME=$HOME/.rvm/rubies/jruby-1.6.6
> RUBY_VERSION=jruby-1.6.6
> IRBRC=$HOME/.rvm/rubies/jruby-1.6.6/.irbrc

And it prepends:

$HOME/.rvm/gems/jruby-1.6.6/bin:$HOME/.rvm/gems/jruby-1.6.6@global/bin

to $PATH