title: How do file descriptors work?
body: <p>Can someone tell me why this does not work? I'm playing around with file descriptors, but feel a little lost.</p>
  
  <pre><code>#!/bin/bash
  echo "This"
  echo "is" &gt;&amp;2
  echo "a" &gt;&amp;3
  echo "test." &gt;&amp;4
  </code></pre>
  
  <p>The first three lines run fine, but the last two error out. Why?</p>