Dedyn.io Update Script

dedyn.sh

#!/bin/bash
# Script by Patrick M. Elsen <pelsen@xfbs.net>
# Updates your dedyn.io dynamic DNS, only if your IP address has changed.
# Licensed under MIT license.
# Uses openDNS IP lookup. Ideally, put this script into a cron job and run hourly.
set -euo pipefail

# dns credentials
dnsuser=yourdedyniousername
dnstoken=yourdedyniotoken

# where to cache ip addresses
ipv4_cache=/var/run/ipv4addr
ipv6_cache=/var/run/ipv6addr

# query current ip addresses
ipv4=$(dig @resolver3.opendns.com myip.opendns.com +short)
ipv6=$(dig @resolver1.ipv6-sandbox.opendns.com AAAA myip.opendns.com +short)

if [[ -f "$ipv4_cache" ]] && [[ -f "$ipv6_cache" ]]; then
    if [[ "$(< $ipv4_cache)" == "$ipv4" ]] && [[ "$(< $ipv6_cache)" == "$ipv6" ]]; then
        exit 0
    fi
fi

# update dyndns
response=$(curl -s --user "$dnsuser.dedyn.io:$dnstoken" "https://update.dedyn.io/?myipv4=$ipv4&myipv6=$ipv6")

if [[ "$response" != "good" ]]; then
    printf "error: %s" "$response"
    exit 1
fi

# store addresses in cache
printf "%s" "$ipv4" > "$ipv4_cache"
printf "%s" "$ipv6" > "$ipv6_cache"

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