title: How does Vim's autoread work?
body: <p><code>:h autoread</code> says:</p>
  
  <blockquote>
    <p>When a file has been detected to have been changed outside of Vim and it has not been changed inside of Vim, automatically read it again.</p>
  </blockquote>
  
  <p>After putting <code>set autoread</code> in my <code>vimrc</code>, I open a file with Vim, switch to another editor, change the file, and wait to see the changes in Vim as well. Nothing happens. I have to use <code>:e</code> to reload the file with the new content.</p>
  
  <p>What did I miss?                                                                <em>I'm using Vim 7.2 on Mac 10.5.8</em></p>