title: Why does my Ruby 'ri' tool not return results in command prompt?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/1587354/ruby-1-9-ri-problem">ruby 1.9 ri problem</a>  </p>
  </blockquote>
  
  
  
  <p>When I try to use Ruby's <code>ri</code> tool in a command prompt window to get help about classes, methods, etc. it seems to always fail. For example if I type:</p>
  
  <pre><code>ri Array
  </code></pre>
  
  <p>I get a message saying:</p>
  
  <pre><code>Updating class cache with 0 classes... Nothing known about Array
  </code></pre>
  
  <p>I am using Vista 64 with Ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32] installed.</p>
  
  <p>What should I do to configure  <code>ri</code> to work?</p>