How to wait in script until device is connected

Question

I have a Sky wireless sensor node and a script which prints the output from the node.

sudo ./serialdump-linux -b115200 /dev/tmotesky1

If I start this script before my pc detects the node, I get the following error:

/dev/tmotesky1: No such file or directory

But if I wait for example 20 seconds, I miss the initial prints (which are important).

Is there a way to detect if the /dev/tmotesky1 exists? Something like

while [ ! -f /dev/tmotesky1 ] ; do sleep 1; print 'Waiting...'; done

Thanks in advance!

Answer 1

Your code indicates that you are using Linux where you can use the hotplugging mechanism.

On generic systems, you can write an udev rule (--> see with udevadmin monitor -e what happens when you attach the device) which starts e.g. a program or writes something into a pipe. When systemd is used, you can start a service (see man systemd.device).

On small/embedded systems it is possible to write a custom /sbin/hotplug program (set in /proc/sys/kernel/hotplug) instead of using udev.