I have three applications, AppA, AppB and AppC, as well as three USB HID keyboard "wedge" barcode scanners, Left, Center, and Right. The scanners are running in continuous scan mode, whenever a barcode is visible, they send the code as an ascii string followed by a CR.

How can I get AppA to read only the Left scanner, AppB read Center, and AppC only read the Right scanner?

The default behavior is that one app has "focus" and all three scanners would dump data to that application, but then I can't tell which scanner saw any given barcode.

The applications would be in C for this project, if that matters, and the OS would likely be CentOS.

The greater application is robotics on the cheap, trying to do navigation in a known environment.

TY!

That sounds like a complicated, tedious inside job to write out.
If it is Linux then linux is linux, and what distro should not matter that much if any.

It should be the desktop being used, or get right down inside of x.

I'd think you'd have to climb into the desktops abilities to tell you which window has focus, then somehow get inside of the app to see if it sent anything. OpenSource you should be able to modify any code to output what it is doing to somewhere else even.

say if you got an app sending data to something, just work in some code within that code to split it off and send you a message to somewhere else that you can get into without disrupting any processes, and inspect to see who is doing what.

I'd take that approach first, messing with the applications source code first to send me information of what it did and when and what else I'd want/need to know.

I'm trying to avoid using the desktop, or X.
The scanners don't provide any identity when they scan, simply spit out the barcode, so reading all three and trying to parse won't work.
If they were serial instead of universal serial, it would be simple, I could attach a process to ttyS0, another to ttyS1, and the last to ttyS2, and then I'd know which process read what scanner and when.
I'm hoping that there is a way to attach to the raw device without going through the HID portion so that I can treat the three sources as three separate sources.