Watch module /sys/module/uvcvideo/refcnt for changes (to trigger action on webcam use)

Question

I would like to switch an On Air sign at my work-from-home office when my webcam is on.

Detecting whether the webcam is on can easily be done via

cat /sys/module/uvcvideo/refcnt 

if it outputs 0 no app is using the webcam, otherwise it is.

I already have a Wifi plug which can be switched using a HTTP GET request.

My only question is: Do I have to poll the output of the above command regularly, or can I get notified in some Bash, Python or PHP script from the kernel?

The idea would be to not generate unnessary system load by polling - or doesn't that matter?

I already tried inotifywait but it does not seem to notice changes on the above pseudo file.

Answer 1

Based on jasonharpers answer I implemented it as a daemon that uses polling

https://github.com/amenk/OnAirDaemon