title: Why does the order of redirection assignments matter for a proxy file descriptor
body: <p>I am learning about redirections in shell right now (reading the posix standard).<br />
  I played a little with the different operators and think I get the hang of it. In the following example, I am creating a new file descriptor and use that as a proxy.
  What I cannot really fathom is why this works:</p>
  <pre><code>exec 6&lt;&gt; ~/Desktop/test &amp;&amp; ls 6&gt;&amp;1 2&gt;&amp;6 1&gt;- | say
  </code></pre>
  <p>but this not:</p>
  <pre><code>exec 6&lt;&gt; ~/Desktop/test &amp;&amp; ls 2&gt;&amp;6 6&gt;&amp;1 1&gt;- | say
  </code></pre>
  <p>The desired result is to read out any errors that occur during <code>ls</code>.</p>