LocomotiveEdit
As an alternative to manually installing Ruby on Rail on Mac OS X Tiger pre-package drag-and-drop installs of everything required are available in the form of Locomotive. See the Locomotive website:
Command line operation
To operate on a Locomotive bundle from the command line you need to set the appropriate environment variables (RUBYLIB, DYLD_FALLBACK_LIBRARY_PATH and HOME). First of all, choose "Command Line Tool…" from the Locomotive "Help" menu and install a symbolic link to the Locomotive command line tool.
You can then type the following command from inside a Rails application root to see the necessary environment variables:
locomotive bash-environment
You can set these environment variables, once again from inside a Rails application root, using:
command `locomotive bash-environment`