Probably my fault, I maybe wasn't clear enough, then the example in the code window I was wondering it was clear enough.
Your command show ALL the outdated packages from updated ports tree, I just need a list of outdated packages in the sense of ports not maintained anymore with relative packages installed in the system, and so the relative packages can't be updated even if they are installed. This is usefull if, for example, you want to run a portmaster round without manually delate a not maintained package.each time it surface, a long and painfull process. If you know those in advance, you can delete them in a batch for example.