#! /bin/sh

if ! [ $2 ] || ! ( echo $2 | grep '\.' >/dev/null )
then
	echo 'Usage: dns_check_address DOMAIN SERVER' 1>&2
	exit 255
fi

A=$(
	dig +trace +short IN A $1 |
	sed '
	/^A / {
		s/^A //
		s/ .*//
		p
	}
	d'
)

if [ "$A" = "" ]
then
	echo "Error: no such domain $1"
	exit 255
fi

B=$(
	echo $2 |
	grep '^[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}$' || 
	{
		dig +trace +short IN A $2 |
		sed '
		/^A / {
			s/^A //
			s/ .*//
			p
		}
		d'
	}
)

if [ "$B" = "" ]
then
	echo "Error: no such server $2"
	exit 255
fi

for C in $A
do
	if ! (
		echo "$B" |
		grep $(
			echo $C |
			sed 's/\./\\./g'
		) 1>/dev/null
	) then
		for C in $B
		do
			if ! (
				echo "$A" |
				grep $(
					echo $C |
					sed 's/\./\\./g'
				) 1>/dev/null
			) then
				echo "Error: domain $1 is not at server $2"
				exit 1
			fi
		done
	fi
done

echo "Domain $1 is at server $2"
exit 0