-size_our=$(zstat +size $tmp)
-[[ -e $ATOM ]] && size_their=$(zstat +size $ATOM) || size_their=0
-[[ $size_our = $size_their ]] || mv $tmp $ATOM
+zstat -A size_our +size $tmp
+size_their=0
+if [[ -e $ATOM ]] ; then
+ zstat -A size_their +size $ATOM
+fi
+[[ ${size_our[1]} = ${size_their[1]} ]] || mv $tmp $ATOM