title: Remove a line from a file using a variable line number
body: <p>This is probably a simple one to answer, but I'm stuck, so here goes.</p>
  
  <pre><code>sed '3d' filename    # (or something like that)
  </code></pre>
  
  <p>I'm having trouble trying to use a <code>$VARIABLE</code> instead of the number.</p>
  
  <p>Anyone know how to get this to work, or any alternative options?</p>