if [ -z $1 ]; then
	logger "$0: blank FROM currency"
	exit
fi
if [ -z $2 ]; then
	logger "$0: blank TO currency"
	exit
fi

# Only bother downloading if it's more than 3 hours old
if [ $(find ~/.cache/"$1$2" -mmin +60) ] ; then
	rate=$(curl "http://rate-exchange-1.appspot.com/currency?from=$1&to=$2" | jshon -e rate)
	if [ $? -ne 0 ] ; then
		logger "$0: curl error"
		exit
	fi
	printf "$1$2: %.4f" $rate > ~/.cache/"$1$2"
fi