Shell script to notify if the GFNB software version changes

gfnb_version.sh

#!/bin/bash

# We will try to determine your GFNB address automatically by using
# your system's gateway address.
#
# If that doesn't work, or you want to override the detected
# value, uncomment the following line and set the value you want
#
# gfnb_ip=192.168.1.1

# Where do you want the notifications sent?
# use /dev/null to turn off email notifications
mail_to=richardjhornsby@gmail.com

# tmp location where logs and state file will be stored
tmp=~/tmp

# Don't change anything below this line #

# Try to guess the gfnb IP address
if [ -z $gfnb_ip ]; then
	os=$(uname)
	case $os in
		'Darwin')
			gateway=$(netstat -rn -f inet | awk '/^default/ {print $2}')
		;;
		'Linux')
			gateway=$(route -n | awk '/^0.0.0.0/ {print $2}')
		;;
		*)
			if [ -z "$gateway" ]; then
				echo 'Unable to reliably determine your gateway address. Please set gfnb_ip'
				exit 1
			fi
		;;
	esac
	gfnb_ip=$gateway
fi

mkdir -p $tmp 2> /dev/null

gfnb_ver=$tmp/gfnb_ver
log=$tmp/gfnb_ver.log

if [ ! -e $gfnb_ver ]; then touch $gfnb_ver; fi

prev_ver=$(cat $gfnb_ver)
curr_ver=$(curl -s "http://$gfnb_ip/content.json?checksum=0&_=0" | ruby -rjson -e 'puts JSON.parse(STDIN.read)["softversion"]')

if [[ ! -z $prev_ver && $prev_ver != $curr_ver ]]; then
	echo "$(date): Version changed to $curr_ver" >> $log
	mail -s "gfnb version change" $mail_to < $log
fi

echo $curr_ver > $gfnb_ver
exit 0