FindUsbTty.sh

#!/bin/bash

if [ "$#" -ne 2 ]; then
	echo "USAGE: $0 VID PID" >&2
	echo "VID & PID specify the vendor and product ID of the desired USB device, given in hex." >&2
	exit -1
fi

StartingDir=$PWD
Vendor=$1
Product=$2


cd /sys/bus/usb/devices

for file in ./*
do
	if [[ "$file" != *":"* ]]
	then
		if [[ `cat $file/idVendor` == "$Vendor" ]]
		then
			if [[ "`cat $file/idProduct`" == "$Product" ]]
			then
				cd "$file"
				file=${file:2}
				for ep in ./$file*
				do
#				if [[ -d "./$file:1.0" ]]
#				then
					if [[ -d "./$ep/tty" ]]
					then
						cd "./$ep/tty"
						for tty in *
						do
							# In rare circumstances, [[ -c "/dev/${tty}" ]] may fail to `stat`, and hence return false,
							# even though the file exists. Hopefully bypassing this check doesn't introduce other issues.
							
							#if [[ -c "/dev/${tty}" ]]
							#then
								echo "/dev/${tty}"
								exit 0
							#fi
						done
					fi
#				fi
				done
				# Should I return an error if the USB was valid but has no TTY?
				exit 2
			fi
		fi
	fi
done
exit 1