How can I determine the correct /dev/input/event* name to monitor or at least fix it to something pre-known?

Question

I am running Raspbian Lite on a Raspberry Pi Zero. It has a touch sensitive LCD display. I have a (perl) program that reads touch events from /dev/input/event* and responds appropriately.

The problem I have is that the event file name sometimes flips between /dev/input/event0 and event1 after a reboot. Both files always exist.

Why does it do that? What sets the filename that is used?

Is there any way that I can detect which file is "active"? (There are no events on the other filename as far as I can tell.)

Answer 1

Look for the presence of a directory named /dev/input/by-path or /dev/input/by-id. Inside these directories there will be links to your hardware that will persist across boot cycles.