Wait until startup script logs it is finished with time threshold

wait_startup_script_to_exit.sh

wait_startup_script_to_finish() {
    vm_name=$1
    vm_zone=$2
    threshold=$(date --date="-5 min" "+%b %_d %H:%M:%S")
    echo -n "Wait for \"$vm_name\" startup script to exit."
    status=""
    while [[ -z "$status" ]]
    do
        sleep 3;
        echo -n "."
        logline=$(gcloud compute ssh $vm_name --zone=$vm_zone --ssh-flag="-q" --command 'tac /var/log/syslog | grep -m 1 "startup-script exit status"' 2>&-)
        timestamp=$(echo $logline | awk {print $1,$2,$3})
        if [(($threshold - $timestamp)) -gt 0]
        then
            status=$(echo $logline | awk '{print $NF}')
        fi
    done
    echo ""
}