test.sh

#!/bin/bash
# Usage: (cat /etc/fstab && sleep 20 && cat /etc/fstab ) | ./test.sh
interval=10
function _do() {
    echo "$@" | cat -n
}
CR='
'
while true
do
    buffer=''
    while read -t ${interval-} line
    do
        buffer="${buffer-}${line-}${CR-}"
    done
    if [[ -z "${buffer-}" ]]; then
        continue
    fi
    _do "${buffer-}"
done