Mavericks(OS X 10.9.2)へまだ入れてなかったのでメモ。
バージョンは4.0.3。
$ gem install rails Fetching: i18n-0.6.9.gem (100%) Fetching: tzinfo-0.3.38.gem (100%) Fetching: minitest-4.7.5.gem (100%) Fetching: activesupport-4.0.3.gem (100%) Fetching: builder-3.1.4.gem (100%) Fetching: rack-test-0.6.2.gem (100%) Fetching: erubis-2.7.0.gem (100%) Fetching: actionpack-4.0.3.gem (100%) Fetching: activemodel-4.0.3.gem (100%) Fetching: arel-4.0.2.gem (100%) Fetching: activerecord-deprecated_finders-1.0.3.gem (100%) Fetching: activerecord-4.0.3.gem (100%) Fetching: mime-types-1.25.1.gem (100%) Fetching: polyglot-0.3.4.gem (100%) Fetching: treetop-1.4.15.gem (100%) Fetching: mail-2.5.4.gem (100%) Fetching: actionmailer-4.0.3.gem (100%) Fetching: thor-0.18.1.gem (100%) Fetching: railties-4.0.3.gem (100%) Fetching: hike-1.2.3.gem (100%) Fetching: tilt-1.4.1.gem (100%) Fetching: sprockets-2.11.0.gem (100%) Fetching: sprockets-rails-2.0.1.gem (100%) Fetching: rails-4.0.3.gem (100%) Successfully installed i18n-0.6.9 Successfully installed tzinfo-0.3.38 Successfully installed minitest-4.7.5 Successfully installed activesupport-4.0.3 Successfully installed builder-3.1.4 Successfully installed rack-test-0.6.2 Successfully installed erubis-2.7.0 Successfully installed actionpack-4.0.3 Successfully installed activemodel-4.0.3 Successfully installed arel-4.0.2 Successfully installed activerecord-deprecated_finders-1.0.3 Successfully installed activerecord-4.0.3 Successfully installed mime-types-1.25.1 Successfully installed polyglot-0.3.4 Successfully installed treetop-1.4.15 Successfully installed mail-2.5.4 Successfully installed actionmailer-4.0.3 Successfully installed thor-0.18.1 Successfully installed railties-4.0.3 Successfully installed hike-1.2.3 Successfully installed tilt-1.4.1 Successfully installed sprockets-2.11.0 Successfully installed sprockets-rails-2.0.1 Successfully installed rails-4.0.3 24 gems installed