Cleaning up MacPorts

It seems as though MacPorts, when upgrading to a new version of an application, leaves the old version behind. After a while, this will eat up quite a bit of your precious hard disk space. There will probably be a lot of ports installed, and only the ones marked "(active)" are used. The rest may be removed. The following commands will keep those "active" only

port installed > list ; sed -e '1'd list | grep -v "active" | while read i ; do sudo port uninstall --follow-dependents $i ; done