if [ $# -ne 5 ]; then
echo "usage: $0 n1 n2 n3 n4 n5"
exit 1
fi
echo -n "dir name: "
read dir
if [ ! -d $dir ]; then
echo "error: invalid dir $dir"
exit 2
fi
sum=0
for i in $@; do
let sum=$sum+$i
done
let avg=$sum/$#
for i in $dir/*.txt; do
echo $avg >> $i
done