title: How do I upgrade Rails?
body: <p>I am new to Ruby <strong>and</strong> Rails, as well as all this command line melarky. So please bear with me.</p>
  
  <p>I have installed, RubyGems, Homebrew, RVM, Rails etc, by following various tutorials.</p>
  
  <p>I think I have all of this going now, but when I type:</p>
  
  <pre><code>rails --version
  </code></pre>
  
  <p>I get, 3.2.12. I notice that Rails 4 is out. How do I upgrade to this version? </p>
  
  <p>If I do:</p>
  
  <pre><code>gem install rails
  </code></pre>
  
  <p>Even doing:</p>
  
  <pre><code>gem update rails
  </code></pre>
  
  <p>I still get 3.2.12.</p>
  
  <p>Any ideas?</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>When trying a few options here, I get this message returned...</p>
  
  <pre><code>Michaels-MacBook-Pro:~ ParanoidAndroid$ gem install rails --version=4.0
  Building native extensions.  This could take a while...
  ERROR:  Error installing rails:
      ERROR: Failed to build gem native extension.
  
      /usr/local/rvm/rubies/ruby-1.9.3-p392/bin/ruby extconf.rb
  *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of
  necessary libraries and/or headers.  Check the mkmf.log file for more
  details.  You may need configuration options.
  
  Provided configuration options:
      --with-opt-dir
      --without-opt-dir
      --with-opt-include
      --without-opt-include=${opt-dir}/include
      --with-opt-lib
      --without-opt-lib=${opt-dir}/lib
      --with-make-prog
      --without-make-prog
      --srcdir=.
      --curdir
      --ruby=/usr/local/rvm/rubies/ruby-1.9.3-p392/bin/ruby
      --with-atomic_reference-dir
      --without-atomic_reference-dir
      --with-atomic_reference-include
      --without-atomic_reference-include=${atomic_reference-dir}/include
      --with-atomic_reference-lib
      --without-atomic_reference-lib=${atomic_reference-dir}/lib
  /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
  You have to install development tools first.
      from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:461:in `try_link0'
      from /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/mkmf.rb:712:in `try_run'
      from extconf.rb:26:in `&lt;main&gt;'
  
  
  Gem files will remain installed in /usr/local/rvm/gems/ruby-1.9.3-p392/gems/atomic-1.1.14 for inspection.
  Results logged to /usr/local/rvm/gems/ruby-1.9.3-p392/gems/atomic-1.1.14/ext/gem_make.out
  </code></pre>
  
  <p>Seems there's an error happening. Any further ideas?</p>
  
  <p>Thanks again everyone!</p>