Update script for dynv6.com to set your IPv4 address and IPv6 prefix

dynv6.sh

#!/bin/sh -e
hostname=$1
device=$2
v6_file=/tmp/.dynv6-"$hostname".addr6
v4_file=/tmp/.dynv6-"$hostname".addr4
[ -e $v6_file ] && v6_old=`cat $v6_file`
[ -e $v4_file ] && v4_old=`cat $v4_file`

if [ -z "$hostname" -o -z "$token" ]; then
    echo "Usage: token=<your-authentication-token> [netmask=64] $0 your-name.dynv6.net [device]"
    exit 1
fi

if [ -z "$netmask" ]; then
    netmask=128
fi

if [ -n "$device" ]; then
    device="dev $device"
fi
v6_address=$(ip -6 addr list scope global $device | grep -v " fd" | sed -n 's/.*inet6 \([0-9a-f:]\+\).*/\1/p' | head -n 1)
v4_address=$(ip -4 addr list scope global $device | grep -v " fd" | sed -n 's/.*inet \([0-9a-f.]\+\).*/\1/p' | head -n 1)

if [ -e /usr/bin/curl ]; then
    bin="curl -fsS"
elif [ -e /usr/bin/wget ]; then
    bin="wget -O-"
else
    echo "neither curl nor wget found"
    exit 1
fi

if [ -z "$v6_address" ]; then
    echo "no IPv6 address found"
else
    # address with netmask
    v6_current=$v6_address/$netmask
    if [ "$v6_old" = "$v6_current" ]; then
        echo "IPv6 address unchanged"
    else
        # send addresses to dynv6
        $bin "http://dynv6.com/api/update?hostname=$hostname&ipv6=$v6_current&token=$token"
        # save current address
        echo $v6_current > $v6_file
    fi
fi

if [ -z "$v4_address" ]; then
    echo "no IPv4 address found"
else
    v4_current=$v4_address
    if [ "$v4_old" = "$v4_current" ]; then
        echo "IPv4 address unchanged"
    else
        # send addresses to dynv6
        $bin "http://ipv4.dynv6.com/api/update?hostname=$hostname&ipv4=$v4_current&token=$token"
        # save current address
        echo $v4_current > $v4_file
    fi
fi