title: cannot redirect stdin in bash
body: <p>I am playing with file descriptors. A common practice is to redirect stdout and stderr using file descriptors, like this:</p>
  
  <pre><code>$ ls &gt;files.txt 2&gt;errors.txt
  </code></pre>
  
  <p>another example might be:</p>
  
  <pre><code>$ echo 'Hello there' &gt; message.txt 2&gt; errors.txt
  </code></pre>
  
  <p>however the following does not work:</p>
  
  <pre><code>$ echo 'Hello There' 0&gt; input_message.txt &gt; output_message.txt 2&gt; errors.txt
  </code></pre>
  
  <p>It seems like the file descriptor 0 is not working as <code>input_message.txt</code> is empty, I'd expect to find the text message <code>Hello There</code> instead.</p>
  
  <p>Why is that ?</p>