Compiling Ruby MRI on Mac OS X

EDIT: include libyaml

UPDATE 2012-05-30: I have successfully installed ruby-1.9.3-p194 (latest stable) using the same procedure.

Mac OS Snow Leopard comes with a pretty old Ruby:

$ ruby --version
ruby 1.8.7 (2010-01-10 patchlevel 249) [universal-darwin11.0]

You can download and compile the latest Ruby from source. You'll need to have XCode and libyaml installed first. Download libyaml from http://pyyaml.org/wiki/LibYAML and extract it in your Source directory:

$ cd Source
$ tar xzf ~/Downloads/yaml-0.1.4.tar.gz
$ cd yaml-0.1.4/
$ CC=clang ./configure --prefix=/usr/local/yaml-0.1.4... output omitted ...
$ make... output omitted ...
$ sudo make install... output omitted ...

Download the latest Ruby from http://www.ruby-lang.org/en/downloads/ and then extract it in your Source directory:

$ cd Source/
$ tar xzf ~/Downloads/ruby-1.9.3-p0.tar.gz
$ cd ruby-1.9.3-p0/

Configure for compilation with clang and installation in /usr/local/:

$ CC=clang LDFLAGS=-L/usr/local/yaml-0.1.4/lib CPPFLAGS=-I/usr/local/yaml-0.1.4/include ./configure --prefix=/usr/local/ruby-1.9.3-p0... output omitted ...

Compile:

$ make... output omitted ...
$ make test... output omitted ...
PASS all 943 tests
... output omitted ...
PASS all 1 tests

(I tried that with the latest stable, ruby-1.9.2-p290, and some tests failed there, so I didn't use it.)

Install:

$ sudo make install... output omitted ...
$ /usr/local/ruby-1.9.3-p0/bin/ruby --version
ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-darwin11.2.0]

You can either always specify the path to it or you can add it to your PATH variable.