Are there linux environment variables which represent each display screen?

Question

I need a way to pipe (¦) a process to a specified display screen.

Answer 1

There should be an environment variable DISPLAY.  If I type "env | grep DISPLAY" it returns "DISPLAY=:0.0"

The general form for the first display on a host is

host.ip.address:0.0

If you have a second screen attached, I think it would be

host.ip.address:0.1

I may be wrong.  I know if I open another Gnome session using Switch User, the DISPLAY variable shows as

host.ip.address:20.0