I looked every where and try some stuff there, but still have something missing.
I have an app made for Rabbit Processors in Dynamic C, then I migrated it to MS Windows VC 6, and I'm now migrating it to Linux.
The app is a POS and in MS Windows let the "users" use the machine, 2 users at a time. This is, while a users sells things using a numpad keyboard, the other user is making the count of money and other stuff with a touch screen.

This is the same app but 2 instances ran with diff initial params.
c:\>pos_mv.exe POS //- for the keyboard user.
c:\>pos_mv.exe RECA //- for the touch screen user.

Well, hope what I have is clear, so I explain my problem now.

I need somehow to read all keyboard events even if the current app is not focused.
I read this but I'm not sure if its the answer to my problem; or if it's there another way to do it.
I'm looking also for something generic, I mean, something that could work in debian, fedora, ubuntu and so on....
I'm not sure right now which Linux to use in the POS machines.
I'm programming it with Gnome, Anjuta in Debian 4; made a Project for XLib, and not for Gnome, so I think that way it would run in KDE to.

Thank you all,