お名前.comのDDNSのIPアドレスを更新するRubyスクリプト(thanks to https://qiita.com/ats124/items/59ec0f444d00bbcea27d)

onamae-ddns-client.rb

require 'socket'
require 'openssl'

include OpenSSL

ONAMAE_DOMAIN = 'ddnsclient.onamae.com'
ONAMAE_PORT   = 65010
ONAMAE_USER   = ENV['ONAMAE_USER']
ONAMAE_PASS   = ENV['ONAMAE_PASS']
HOSTNAME = ENV['ONAMAE_HOST']   # e.g. ddnsclient
DOMNAME  = ENV['ONAMAE_DOMAIN'] # e.g. onamae.com
IPADDR   = `curl inet-ip.info`.strip

tcp = TCPSocket.new(ONAMAE_DOMAIN, ONAMAE_PORT)
@socket = SSL::SSLSocket.new(tcp)
@socket.connect

def check_responce
  res = @socket.gets.strip
  raise "error: #{res}" unless res == '000 COMMAND SUCCESSFUL'
  @socket.gets
end

check_responce

@socket.puts 'LOGIN'
@socket.puts "USERID:#{ONAMAE_USER}"
@socket.puts "PASSWORD:#{ONAMAE_PASS}"
@socket.puts '.'

check_responce

@socket.puts 'MODIP'
@socket.puts "HOSTNAME:#{HOSTNAME}"
@socket.puts "DOMNAME:#{DOMNAME}"
@socket.puts "IPV4:#{IPADDR}"
@socket.puts '.'

check_responce

@socket.puts 'LOGOUT'
@socket.puts '.'
check_responce

END {
  tcp.close
  @socket.close
  puts 'connection closed'
}