namecheap-dns-update

#!/bin/bash
set -e

hosts=()

hosts[0]="<host> <domain> <password>"


cache_dir=/var/lib/misc/namecheap-dns-update

mkdir -p "$cache_dir"

current_ip=$(dig -4 +short myip.opendns.com @resolver1.opendns.com)

for host in "${hosts[@]}"
do
    host=($host)

    cache_file="$cache_dir/${host[0]}.${host[1]}"
    if [ -f "$cache_file" ]
    then
        last_ip=$(<"$cache_file")
    else
        last_ip="?"
    fi

    if [ "$last_ip" != "$current_ip" ]
    then
        response=$(wget -qO- "https://dynamicdns.park-your-domain.com/update?host=${host[0]}&domain=${host[1]}&password=${host[2]}&ip=${current_ip}")
        if echo "$response" | grep -q "<ErrCount>0</ErrCount>"
        then
            echo "Server DNS record updated for ${host[0]}.${host[1]} : ${last_ip} -> ${current_ip}"
            echo "$current_ip" > "$cache_file"
        else
            reason=$(echo "$response" | sed -En "s/.*<Err1>(.+)<\/Err1>.*/\1/p")
            echo "Server DNS record update FAILED for ${host[0]}.${host[1]} : ${reason}"
        fi
    fi
done