當執行gem install rails時報錯，報錯資訊：

 Building native extensions.  This could take a while...
    ERROR:  Error installing rails:
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


    Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/atomic-1.1.14 for inspection       
    Results logged to /Library/Ruby/Gems/2.0.0/gems/atomic-1.1.14/ext/gem_make.out

解決辦法

1. gem update --system
2. sudo apt-get install ruby-dev