upgrade_ruby.md

1. Install Xcode

2. Use XCode to install Command Line Utilities (GCC)

Open Xcode. Click the "Xcode" button in the top left of the screen near the Apple logo, then click "Preferences", then click "Downloads".

3. Install rbenv:

$ git clone git://github.com/sstephenson/rbenv.git ~/.rbenv
$ echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(rbenv init -)"' >> ~/.bash_profile

4. Install ruby-build:

$ mkdir -p ~/.rbenv/plugins
$ git clone git://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
$ source ~/.bash_profile

5. Compile Ruby

$ env CC=/usr/bin/gcc rbenv install 1.9.3-p362
$ rbenv global 1.9.3-p362
$ rbenv rehash

6. Verify it works:

$ ruby -v
ruby 1.9.3p362 (2012-12-25 revision 38607) [x86_64-darwin12.2.1]