title: What does the "D" command do in sed?
body: <p>I have read the <a href="https://www.gnu.org/software/sed/manual/sed.html#The-_0022s_0022-Command" rel="nofollow noreferrer"><code>sed</code></a> manual for the <code>D</code> command. There it says:</p>
  
  <blockquote>
    <p>D </p>
    
    <p>If pattern space contains no newline, start a normal new cycle as if
    the d command was issued. Otherwise, delete text in the pattern space
    up to the first newline, and restart cycle with the resultant pattern
    space, without reading a new line of input.</p>
  </blockquote>
  
  <p>But I do not know how to use it.</p>
  
  <pre class="lang-none prettyprint-override"><code>$ seq 5 | sed D
  </code></pre>
  
  <p>The output is nothing.</p>