#!/bin/bash

declare -i result=0
declare -i i=0
re='^[0-9]+$'
while read line
do
    if ! [[ $line =~ $re ]] ; then
        echo "error: Not a number" >&2
        exit 0
    else
        let result=result+line
        let i=i+1
    fi
done < "${1:-/dev/stdin}"
echo $result
echo $i
bc -l <<< $result/$i