Operating systems let you know when a device change has happened. You can even cache this where you pool the first time for the initial set of data and then you just check when a device is plugged in to update your knowledge of the state of the world.

I would imagine that’s what’s done if you’re running udev but maybe SDL doesn’t do that.

As has been noted in another subthread, SDL can do this but apparently the particular statically linked version shipped with Papers Please is compiled without udev or inotify support and has to fallback to manual checking.