title: edit XML file in terminal
body: <p>I have a server running on Linux system, and I want to edit an XML file of Imagemagick.</p>
  
  <p>The file content is:</p>
  
  <pre><code>&lt;policymap&gt;
    &lt;policy domain="..." rights=".." pattern="...." /&gt;
    &lt;policy domain="..." rights=".." pattern="...." /&gt;
  ..
  ..    
  &lt;/policymap&gt;
  </code></pre>
  
  <p>So, I want to add this line:</p>
  
  <pre><code>  &lt;policy domain="coder" rights="read | write" pattern="PDF" /&gt;
  </code></pre>
  
  <p>Please how can I do it.</p>
  
  <p>Thank you.</p>