#!/bin/bash
#
# get-free-dev.sh: returns the first free device name (with number) of a basename
#
# Example (silly): 
# ~$ get-free-dev.sh input/js
# input/js2
#  js0 and js1 are already used by 2 joysticks. A dumb example because the basic
#  functionality is already like this.
# 
# Usefull example with multiple playstation joystick adapters:
# ~$ get-free-dev.sh input/js-ps
# input/js-ps0
#
# The first js-ps (joystick on playstation adapter) has been plugged. When another
# of those adapter gets plugged the result is input/js-ps1. When js-ps0 gets removed
# and another gets inserted the now free js-ps0 will be used again.
# This lets you have your own "class" of devices similar to "js" "mouse" "event" etc.
#
# Why not %n in udev: When you have also other joysticks, the number is not continuous
# for the same basename: /dev/input/js-foobar0 /dev/input/js-zonk1 /dev/input/js-ps2 
# Why not %e: Doesn't reuse old numbers and increases pointless on replugging.
#
# udev rule example for a playstation 2 joystick usb adapter:
# BUS="usb", KERNEL="js*", SYSFS{product}="SmartJoy PLUS Adapter", PROGRAM="/etc/udev/scripts/get-free-dev.sh input/js-ps", SYMLINK="%c"

DEV='/dev'

if [ -n "${1}" ]; then
	DEVBASE="${1}"
else
	echo "Usage: `basename ${0}` device-basename"
	exit 1
fi

i=0

while [ -z "${FREEDEV}" ]; do
	if ! egrep -q "^(N|S):${DEVBASE}${i}$" ${DEV}/.udevdb/*; then
		FREEDEV="${DEVBASE}${i}"
	else
		i=$(($i+1))
	fi
done	

echo "${FREEDEV}"