Linux bash script for updating dns on godaddy dynamically. You need a developer account to access the godaddy api to get your secret and token.

godaddy_ddns.sh

#!/bin/bash

# This script is used to check and update your GoDaddy DNS server to the IP address of your current internet connection.
# Special thanks to mfox for his ps script
# https://github.com/markafox/GoDaddy_Powershell_DDNS
#
# First go to GoDaddy developer site to create a developer account and get your key and secret
#
# https://developer.godaddy.com/getstarted
# Be aware that there are 2 types of key and secret - one for the test server and one for the production server
# Get a key and secret for the production server
# 
#Update the first 4 variables with your information
 
domain=""   # your domain
name=""     # name of A record to update
key=""      # key for godaddy developer API
secret=""   # secret for godaddy developer API

headers="Authorization: sso-key $key:$secret"

# echo $headers

result=$(curl -s -X GET -H "$headers" \
 "https://api.godaddy.com/v1/domains/$domain/records/A/$name")

dnsIp=$(echo $result | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b")
# echo "dnsIp:" $dnsIp

# Get public ip address there are several websites that can do this.
ret=$(curl -s GET "http://ipinfo.io/json")
currentIp=$(echo $ret | grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b")
# echo "currentIp:" $currentIp

 if [ $dnsIp != $currentIp ];
 then
#	echo "Ips are not equal"
	request='{"data":"'$currentIp'","ttl":3600}'
#	echo $request
	nresult=$(curl -i -s -X PUT \
 -H "$headers" \
 -H "Content-Type: application/json" \
 -d $request "https://api.godaddy.com/v1/domains/$domain/records/A/$name")
#	echo $nresult
fi

request='[ { "data":"$currentIp", "ttl": 3600} ]'

^^ needs more square brackets! (based on https://developer.godaddy.com/doc/endpoint/domains#/v1/recordReplaceTypeName)

Script didn't work for me. I had to add record type to the request field:
request="[{\"data\":\"$currentIp\",\"ttl\":600,\"type\":\"A\"}]"

This no longer works unless you have 20 or over (or maybe 50 or over) domains with GoDaddy as they have disabled the API without telling anyone. You will get a "Authenticated user is not allowed access" response.