I have managed to ham fist a decent answer to the following problem but I am absolutely certain that there is an easier or more elegant way to do this so here goes.

I have three AD groups and users are members of all, several or none of them depending.  What I am trying to achieve is a count of all the unique users in these three groups.

I have been trying to use the official tools from Server 2008 R2 to do this and was able to get a result by running a get-adgroupmember for each group, exporting/appending to a text file, sorting and then piping to get-unique.  This works but if I run a count against this it includes a count of the two separator lines at the begining of the text file.  Not a real problem but annoying.

Is there a better way to do this?  I was looking at a compare-object style approach but this only compares two objects.

The commands I ran so far:

First command ran for each group in question:

get-adgroupmember -Identity "Office 2007 SP2" | ft -Property samaccountname | out-file -Append users.txt

Then:

get-content users.txt | sort | get-unique > unique.txt

followed by a count of that text file.  Longwinded but I can't seem to think of a way to do this without resorting to using Quest tools.  Any help greatly appreciated.