Mac(Mavericks)でrubyでもと思ってみたらこんなエラーが。 $ gem install json Building native extensions. This could take a while... ERROR: Error installing json: ERROR: Failed to build gem native extension. /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/include/ruby.h解決策をググってみ