Handle redisplay edge case. With motion events when entering a frame and the minibuffer is active, row and column can be zero, and there aren't any runes.

#!/bin/sh
if
test -r $2
then
if
cmp $1 $2 > /dev/null
then
echo $2 is unchanged
rm -f $1
else
mv -f $1 $2
fi
else
mv -f $1 $2
fi