Shell script to detect file or directory has changed using ls, sha1sum, mv and cmp

changed

#! /bin/sh

checksum=`echo $@ | sha1sum - | cut -d ' ' -f 1`

if ! [ -e /tmp/$checksum.ls-ZlaR ]
then
	if ! ls -ZlaR $@ > /tmp/$checksum.ls-ZlaR
	then
		echo changed: could not create /tmp/$checksum.ls-ZlaR 1>&2
		exit 1
	fi
fi

if ! mv /tmp/$checksum.ls-ZlaR /tmp/$checksum.ls-ZlaR.ref
then
	echo changed: could not rename /tmp/$checksum.ls-ZlaR to /tmp/$checksum.ls-ZlaR.ref 1>&2
	exit 1
fi

if ! ls -ZlaR $@ > /tmp/$checksum.ls-ZlaR
then
	echo changed: could not create /tmp/$checksum.ls-ZlaR 1>&2
	exit 1
fi

if cmp -s /tmp/$checksum.ls-ZlaR /tmp/$checksum.ls-ZlaR.ref
then
	exit 0
fi

exit 1