duckdns

#!/bin/bash

LANG=en_US.UTF-8

LAST_IP="$HOME/.duckdns/last-ip"
CONFIG="$HOME/.duckdns/config"

if [ -f "$CONFIG" ]; then
    source "$CONFIG"
else
    logger -t duckdns "Configuration not found"
    exit 1
fi

if [ ! -f "$LAST_IP" ]; then
    if NEW_IP="$(dig +short myip.opendns.com @208.67.222.222)"; then
        echo "$NEW_IP" > "$LAST_IP"
        logger -t duckdns "Initialization succeeded, domain: $DOMAIN.duckdns.org, IP: $NEW_IP"
    else
        logger -t duckdns "Unable to detect the public IP address"
        exit 1
    fi
fi

while true; do
    if CURRENT_IP="$(dig +short myip.opendns.com @208.67.222.222)"; then
        if [ "$CURRENT_IP" != "$(< $LAST_IP)" ]; then
            if RESULT="$(curl -s "https://www.duckdns.org/update?domains=$DOMAIN&token=$TOKEN&ip=$CURRENT_IP")"; then
                if [ "$RESULT" = "OK" ]; then
                    echo "$CURRENT_IP" > "$LAST_IP"
                    logger -t duckdns "Update succeeded, new IP: $CURRENT_IP"
                else
                    logger -t duckdns "Update failed, HTTP API error"
                fi
            else
                logger -t duckdns "Update failed, unable to connect"
            fi
        fi
    else
        logger -t duckdns "Unable to detect the public IP address"
    fi
    sleep $INTERVAL
done