ruby version on macOS Sierra
ruby --version says:


  ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin16]


macOS Sierra 10.12 (16A323) release installed from the App Store with XCode 8 installed

Update: macOS 10.13.3 has


  ruby 2.3.3p222 (2016-11-21 revision 56859) [universal.x86_64-darwin17]