DDNS in Cloudflare using bash/curl/jq/ipify - Only calls Cloudflare when IP changes and ipify has no rate limit so can be run as often as you like. Requires an ini file in the same format as certbot cloudflare-dns plugin

update-dns.sh

#!/usr/bin/env bash

ini_file=$1
dns_zone=$2
domain=$3

function load_ini_value {
    filename=$1
    property=$2
    variable=$3

    declare -g ${variable}=$(source <(grep ${property} ${filename} | sed 's/ *= */=/g'); echo ${!property})
}

load_ini_value ${ini_file} dns_cloudflare_email email
load_ini_value ${ini_file} dns_cloudflare_api_key api_key

function get_zone_id {
    variable=$1

    declare -g ${variable}=$(curl -sS https://api.cloudflare.com/client/v4/zones?name=${dns_zone} \
                                  -H "X-Auth-Email: ${email}" \
                                  -H "X-Auth-Key: ${api_key}" \
                                  -H "Content-Type: application/json" \
                             | jq -r .result[0].id)
}

function get_record_id {
    local zone_id=$1
    id_variable=$2
    ip_variable=$3

    local result=$(curl -sS https://api.cloudflare.com/client/v4/zones/${zone_id}/dns_records \
                                  -H "X-Auth-Email: ${email}" \
                                  -H "X-Auth-Key: ${api_key}" \
                                  -H "Content-Type: application/json")
    declare -g ${id_variable}=$(echo ${result} | jq -r ".result[] | select(.name == \"${domain}\" and .type == \"A\") | .id")
    if [[ ! -z "${ip_variable}" ]]; then
        declare -g ${ip_variable}=$(echo ${result} | jq -r ".result[] | select(.name == \"${domain}\" and .type == \"A\") | .content")
    fi
}

function update_dns_ip {
    local zone_id=$1
    local record_id=$2
    local new_ip=$3
    local variable=$4


    declare -g ${variable}=$(curl -sS -X PUT https://api.cloudflare.com/client/v4/zones/${zone_id}/dns_records/${record_id} \
                                  -H "X-Auth-Email: ${email}" \
                                  -H "X-Auth-Key: ${api_key}" \
                                  -H "Content-Type: application/json" \
                                  --data "{\"type\":\"A\",\"name\":\"${domain}\",\"content\":\"${new_ip}\",\"proxied\":true}")
}

if [[ ! -f .dns-ip ]]; then
    get_zone_id zone_id
    get_record_id ${zone_id} record_id record_ip
    echo $record_ip > .dns-ip
fi

last_ip=$(<.dns-ip)

external_ip=$(curl -sS https://api.ipify.org/)

if [[ "${external_ip}" != "${last_ip}" ]]; then
    echo "IP has change, updating from ${last_ip} to ${external_ip}"

    if [[ -z "${zone_id}" ]]; then
        get_zone_id zone_id
    fi
    if [[ -z "${record_id}" ]]; then
        get_record_id ${zone_id} record_id
    fi

    update_dns_ip $zone_id $record_id $external_ip result

    if [[ $(echo ${result} | jq -r .success) == "true" ]]; then
        echo "SUCCESS"
    else
        echo "FAILURE"
        echo ${result} | jq .
        exit 1
    fi
else
    echo "No change"
fi