Install RubyGems

RubyGems is a package manager for Ruby projects, and there are many useful libraries (including Rails) available as Ruby packages, or gems. Installing RubyGems should be easy once you install Ruby. In fact, if you have installed RVM, you already have RubyGems, since RVM includes it automatically:

If you don’t already have it, you should download RubyGems, extract it, and then go to the rubygems directory and run the setup program:

(If you get a permissions error here, recall from Section 1.1.3 that you may have to use sudo.) If you already have RubyGems installed, you should make sure your system uses the version used in this tutorial:

Freezing your system to this particular version will help prevent conflicts as RubyGems changes in the future. When installing gems, by default RubyGems generates two different kinds of documentation (called ri and rdoc), but many Ruby and Rails developers find that the time to build them isn’t worth the benefit. (Many programmers rely on online documentation instead of the native ri and rdoc documents.) To prevent the automatic generation of the documentation, I recommend making a gem configuration file called .gemrc in your home directory as in Listing 1.1 with the line in Listing 1.2. (The tilde ‘‘˜’’ means ‘‘home directory,’’ while the dot . in .gemrc makes the file hidden, which is a common convention for configuration files. )

 Here subl is the command-line command to launch Sublime Text on OS X, which you can set up using the Sublime Text 2 documentation for the OS X command line. If you’re on a different platform, or if you’re using a different editor, you should replace this command as necessary (i.e., by double-clicking the application icon or by using an alternate command such as mate, vim, gvim, or mvim). For brevity, throughout the rest of this tutorial I’ll use subl as a shorthand for ‘‘open with your favorite text editor.’’