MikroTik Script: DuckDNS.org DDNS Update

#---------------------------------------------------SCRIPT INFORMATION----------------------------------------------------
#
# Script:  Marthur's DuckDNS.org Dynamic DNS Update Script
# Version: 1.0
# Updated: 10/30/2017
# Created: 10/30/2017
# Author:  Marthur Jones
# Website: https://www.marthur.com
#
#-----------------------------------------------TESTED USING THE FOLLOWING------------------------------------------------
#
# Hardware: CCR1009-7G-1C-1S+
# Firmware: v3.41
# RouterOS: v6.40.4
#
# This script is to be used in conjuction with DuckDNS.org's Dynamic DNS Service. It is to be scheduled/ran on a Mikrotik 
# router. Unlike the original version, this script does not use any global variables, instead it compares the current IP
# of the WAN interface with the resolved (DNS) IP of the users DuckDNS.org's FQDN (e.g. mysudbdomain.duckdns.org).
#
#----------------------------------------------MODIFY THIS SECTION AS NEEDED----------------------------------------------

# DuckDNS Full Domain (FQDN)
:local duckdnsFullDomain "mysubdomain.duckdns.org"

# DuckDNS Sub Domain
:local duckdnsSubDomain "mysubdomain"

# DuckDNS Token
:local duckdnsToken "7311de01-1830-454d-be05-9e8f2f99f4ce"

# The interface name with the assigned dynamic IP address (usually the WAN interface).
:local wanInterface "Ether0-Gateway"

# Log destination
:local logDestination "/disk1/logs/"

#-------------------------------------------------------------------------------------------------------------------------

:log warning message="START: DuckDNS.org DDNS Update"

:if ([/interface get $wanInterface value-name=running] = true) do={

#   Get the previous IP via DNS resolution.
    :local previousIP [:resolve "$duckdnsFullDomain"]

#   Get the current IP on the WAN interface.
    :local currentIP [/ip address get [find interface="$wanInterface" disabled=no] address]

#   Strip net mask from IP address.
    :for i from=([:len $currentIP] - 1) to=0 do={
        :if ([:pick $currentIP $i] = "/") do={
            :set currentIP [:pick $currentIP 0 $i]
        }
    }

    :log info "DuckDNS: DNS IP ($previousIP), interface IP ($currentIP)"
    
    :if ($currentIP != $previousIP) do={
        :log info "DuckDNS: Current IP $currentIP is not equal to previous IP, update needed"
        :log info "DuckDNS: Sending update for $hostname"
        /tool fetch mode=https keep-result=yes dst-path=($logDestination . "duckdns-ddns-update.txt") address=[:resolve www.duckdns.org] port=443 host=www.duckdns.org src-path=("/update?domains=" . $duckdnsSubDomain . "&token=" . $duckdnsToken . "&ip=" . $currentIP);
        :log info "DuckDNS: Host $hostname updated on DuckDNS with IP $currentIP"
    }   else={
        :log info "DuckDNS: Previous IP $previousIP is equal to current IP, no update needed"
        }

}   else={
    :log info "DuckDNS: $wanInterface is not currently running, unable to verify and/or update IP."
    }
    
:log warning message="END: DuckDNS.org DDNS Update"