6tunnel_command.sh

#!/bin/sh

ipv6="$2"

start() {
        echo -n "Starting Tunnels: "
                echo "$ipv6" | awk '{print "/usr/bin/6tunnel 8080 "$1" 8080"}' | /bin/sh
                echo "$ipv6" | awk '{print "/usr/bin/6tunnel 21 "$1" 21"}' | /bin/sh
                echo "$ipv6" | awk '{print "/usr/bin/6tunnel 443 "$1" 443"}' | /bin/sh
                return
}

stop() {
        echo -n "Shutting down Tunnels: "

        killall 6tunnel
        return
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
esac

exit 0

Instead of
echo "$ipv6" | awk '{print "/usr/bin/6tunnel 8080 "$1" 8080"}' | /bin/sh
just write
/usr/bin/6tunnel 8080 "${ipv6}" 8080.