On Thu, May 19, 2022 at 08:54:52AM +0100, Tixy wrote:
> To find the device ID my bash script scans the USB serial numbers
> looking for the one I'm interested in...
>
> pushd /sys/bus/usb/drivers/usb >/dev/null
> for f in **/serial
> do
> if [ "$(cat $f)" = MY_SERIAL_NUMBER ]; then
> ID=${f%%/*}
> fi
> done
> popd >/dev/null
>
> if [ "$ID" = "" ]; then
> echo "Can't find device"
> exit 1
> fi
>
> There's no doubt better ways of doing the above, but it works for me.
> (Looking at it now I'd get rid of the pushd/popd by using an extra
> string splice operation and that use of ** probably needs something
> doing to it to cope with spaces in paths)
1) For ** to work, you need to do "shopt -s globstar" somewhere before it.
Other issues:
2) You didn't check the success of your pushd. If it fails, you could
theoretically run the rest of the script from the wrong directory.
3) "$f" should be quoted, in "$(cat "$f")". Or, if you'd like to avoid
forking a cat(1) for every USB serial device, you could do something
like:
for f in **/serial
do
read -r serial < "$f"
if [ "$serial" = MY_SERIAL_NUMBER ]; then
id=${f%%/*}
fi
done
4) There's no reason to keep reading if you've already found the desired
id, so you could add a "break" right after the id=${...} part.
