#!/bin/bash
loud=
target=${1:-2601:401:8200:2d4c:c6a5:6c8c:1304:bcf7}

process()
{
        state=
        while true
        do
                if read -t 5 line
                then
                        if [ "$loud" ]
                        then
                                printf '%s\n' "$line"
                        fi
                        case "$line" in
                                PING*) continue ;;
                        esac
                        if [ "$state" = on ]
                        then
                                continue
                        else
                                date +'%c Online.'
                                state=on
                        fi
                elif [ $? -gt 128 ] # read timeout
                then
                        if [ "$state" = off ]
                        then
                                continue
                        else
                                date +'%c Offline.'
                                state=off
                        fi
                else # non-timeout read error
                        break
                fi
        done
}

ping -n "$target" | process