title: "ps aux" works but "ps -aux" doesn't
body: <p>This might seem like a silly question but I haven't been able to find a clear answer.</p>
  
  <p><a href="http://www.linfo.org/ps.html">This website</a> states that the dash is optional in </p>
  
  <pre><code>ps aux
  </code></pre>
  
  <p>However, <code>ps aux</code> works but <code>ps -aux</code> brings up the error <code>no user named 'x'</code>.  Any ideas what the issue may be here?  Running Mac 10.8.2.  Thanks</p>