title: change user in sudo bash script
body: <p>In a bash script that is called with sudo i am calling:</p>
  
  <p>/usr/bin/firefox -new-tab <a href="http://stackoverflow.com">http://stackoverflow.com</a></p>
  
  <p>but then i get the message:</p>
  
  <blockquote>
    <p>Firefox is already running, but is not
    responding. To open a new window, you
    must first close the existing Firefox
    process, or restart your system</p>
  </blockquote>
  
  <p>this is, i guess, because the script is called by sudo and firefox by the normal user.
  if i would call the command without sudo it works.</p>
  
  <p>so how can i switch back to the normal user in a sudo called script?</p>