title: Command not found after pipe
body: <p>I'm using OS X Mavericks with zsh (technically the package oh-my-zsh). </p>
  
  <p>I've been facing this bug for some time now and haven't found a way to fix it. Sometimes when I pipe a command it just says command not found.</p>
  
  <p>For example, when I do a nmap network list scan like so <code>nmap -sL 192.168.2.0/24 | grep ')'</code> I sometimes get the error <code>zsh: command not found:  grep</code>. Even when I use arrow up button it won't work, so I have to rewrite the command, exactly the same, and it will work.</p>
  
  <p>It is really annoying and it has happened occasionally with other commands and mostly after a pipe.</p>
  
  <p>Any idea why this is occurring?</p>