Wait for reboot update

#!/bin/bash

HOST=$1 # Resolvable host name or IP address of remote host.
TIMEOUT=$2

format_time() {
    seconds=$1
    time=`printf "%02d-%02d-%02d\n" $[seconds/3600] $[$[seconds%3600]/$[60]] $[$[seconds%3600]%$[60]]`
    echo $time
}

wait_for_reboot() {
    cnt=0
    host=$1
    start=`date +%s`

    ping -c 1 -n -w 1 $host | grep "1 received" > /dev/null
    [ $? != 0 ] && status=down || status=up
    [ "$2" == "" ] && timeout=90 || timeout=$2

    echo
    echo -n "Waiting for host \"$host\" to come online: "

    while true; do
        ping -c 1 -n -w 1 $host | grep "0 received" > /dev/null
        result=$?

        echo -n "."
        cnt=$((cnt+1))
        [ $result == 1 ] && sleep 1 || status=down

        [ $result == 1 ] && [ $status == "down" ] && {
            sleep 1
            end=`date +%s`
            echo -e "\nHost \"$host\" is back online, reboot time: $(format_time $[end-start])"
            break
        } || [ $cnt -ge $timeout ] && {
            end=`date +%s`
            echo -e "\nRemote host \"$host\" did not reboot. [timeout > $timeout]\n"
            break
        }
    done
}

echo
ssh root@$HOST reboot

wait_for_reboot $HOST $TIMEOUT