title: In MacPorts, how to identify and uninstall unused library ports?
body: <p>Lots of ports in macports are installed as library dependencies of the other (application) ports, but uninstall those application ports doesn't uninstall corresponding library dependencies.  As time goes by, lots of such library ports become orphon and is just a waste of space.  So I wonder if there is a way to find them out.</p>
  
  <p>Thanks.</p>