Is there a way to compare what is in the ports tree with what is installed?

[Pollywog]

On Monday 05 November 2007 02:04:39 Robert Huff wrote:
> Brett Davidson writes:
> >  ie. If I had a particular version of the ports tree on a server,
> >  how could I check to see if any of the programs in that tree were
> >  actually installed?
> >
> >  Is there a simple command or sequence of commands to do this?
>
> 	dir /var/d/pkg | grep <portname>

My Linux systems have a "dir" command but my FreeBSD does not.
Is there something I need to install?