do-dns-update.rb

#!/usr/bin/env ruby
require 'rubygems'
require 'digitalocean'
require 'yaml'

if ARGV.length < 2
  puts "Usage:\n"
  puts "      do-dns-update domain subdomain\n\n"
  exit
end

current_ip = File.read("#{ENV['HOME']}/.wan_ip").strip rescue ""
wan_ip = `curl ifconfig.me 2>/dev/null`.strip

# Read the 
domain_name = ARGV[0]
sub_domain_name = ARGV[1]

if ENV['DIGITALOCEAN_CLIENTID'] and ENV['DIGITALOCEAN_APIKEY']
  Digitalocean.client_id  = ENV['DIGITALOCEAN_CLIENTID']
  Digitalocean.api_key = ENV['DIGITALOCEAN_APIKEY']
elsif File.exist? "#{ENV['HOME']}/.digitalocean"
  yaml = YAML.load_file "#{ENV['HOME']}/.digitalocean"
  if yaml["client_id"] and yaml["api_key"]
    Digitalocean.client_id  = yaml['client_id']
    Digitalocean.api_key = yaml['api_key']
  end
else
  puts "Set DIGITALOCEAN_CLIENTID and DIGITALOCEAN_APIKEY or create ~/.digitalocean,\n with client_id and api_key as YAML property names."
end

if current_ip != wan_ip
  all_domains = Digitalocean::Record.all(domain_name)
  if all_domains.status == "OK"
    sub_domain_id = all_domains.to_h[:records].select{|r| r["name"] == sub_domain_name }.first["id"]
    Digitalocean::Record.edit(domain_name, sub_domain_id, {data: wan_ip})
    File.open("#{ENV['HOME']}/.wan_ip", "w") do |f|
      f.print wan_ip
    end
    puts wan_ip
  elsif all_domains.status == "ERROR" and all_domains.error_message == "Access Denied"
    puts "Access denied - set DIGITALOCEAN_CLIENTID and DIGITALOCEAN_APIKEY to the\nDigital Ocean client id and API key"
  else
    puts "unknown error"
  end
else
  puts "wan ip is unchanged : #{wan_ip}"
end