title: I see gem in "gem list" but have "no such file to load"
body: <p>I am on Ubuntu10</p>
  
  <pre><code>sudo apt-get install ruby1.9.1-full
  </code></pre>
  
  <p>then download sources of rubygem 1.3.7 and install it</p>
  
  <pre><code>sudo ruby setup.rb
  </code></pre>
  
  <p>then, for example, install sinatra</p>
  
  <pre><code>sudo gem install sinatra
  </code></pre>
  
  <p>Finally open irb and type</p>
  
  <pre><code>require "rubygems"
  require "sinatra"
  </code></pre>
  
  <p>and get error</p>
  
  <pre><code>LoadError: no such file to load -- sinatra
      from (irb):2:in `require'
      from (irb):2
      from /usr/bin/irb:12:in `&lt;main&gt;'
  </code></pre>