aside from that, my first guess is that the directory /sys/class/net/mon0/device/channels doesn't even exist. In fact, my second guess would be that the directory /sys/class/net/mon0/ doesn't exist.
of course, I have been wrong upon occasion, but that's my story and I'm sticking to it. i suspect you need to modify the script so that it looks at interfaces that you actually have. eth0, wlan0..etc etc etc