title: What actually the meaning of "-n" in sed?
body: <p>According to <a href="http://linux.about.com/od/commands/l/blcmdl1_sed.htm" rel="noreferrer">http://linux.about.com/od/commands/l/blcmdl1_sed.htm</a></p>
  
  <blockquote>
    <p>suppress automatic printing of pattern
    space</p>
  </blockquote>
  
  <p>I've tested with or without <code>-n</code>, sed will produce same result</p>
  
  <p>I dont understand what space does it means.</p>