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$2" -mmin +180) ] ; then
	rate=$(curl "http://rate-exchange-1.appspot.com/currency?from=$1&to=$2" | jshon -e rate)
	echo "$1$2: $rate" > ~/.cache/"$1$2"
fi