How do I measure the RAM usage of desktop environments?

I would like to measure the RAM usage of several desktop environments (including Cinnamon, GNOME, KDE, LXDE, LXQt, MATE and Xfce) running on my Sabayon machine. I would prefer a command-line way of checking RAM usage, if possible. I have tried using this [ps_mem.py](https://github.com/pixelb/ps_mem/) script (by running python ps_mem.py -p Cinnamon for Cinnamon, for example) but unfortunately it requires PIDs for programs and will not simply accept the name of the DE and I'm not sure which programs belong to my DE and which do not.