und.go

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"time"
)

var (
	fVersion  = flag.Bool("v", false, "print version information and exit")
	fKey      = flag.String("k", "12345", " To be replaced by your unique API key. Visit the API Manager page within your account for details.")
	fDomain   = flag.String("d", "namesilo.com", "The domain associated with the DNS resource record to modify")
	fHost     = flag.String("h", "www", "The hostname to use (there is no need to include the \".DOMAIN\")")
	fInterval = flag.Duration("i", 300*time.Second, "The seconds of updating interval")
)

var version = "None"

func main() {
	flag.Parse()
	if *fVersion {
		fmt.Println(version)
		os.Exit(0)
	}
	updateDNSLoop()
}

func updateDNSLoop() {
	tick := time.NewTicker(*fInterval)
	defer tick.Stop()
	for {
		select {
		case <-tick.C:
			err := doUpdateDNS(*fDomain, *fHost, *fKey)
			if err != nil {
				log.Printf("[%v] update DNS record failed, domain:%s, host:%s, error:%v", time.Now().Format(time.RFC3339), *fDomain, *fHost, err)
			}
		}
	}
}

func doUpdateDNS(domain, host, key string) error {
	listResp, err := dnsList(domain, key)
	if err != nil {
		return err
	}

	// find the one need to be updated
	fullHost := host + "." + domain
	for _, item := range listResp.ListReply.DNSRecords {
		if item.Host == fullHost {
			if item.Value != listResp.Request.IP {
				// update record
				log.Printf("[%v] host: %s, update old IP: %s to new IP: %s", time.Now().Format(time.RFC3339), item.Host, item.Value, listResp.Request.IP)
				err = dnsUpdate(key, domain, item.RecordID, host, listResp.Request.IP)
				if err != nil {
					return err
				}
			} else {
				log.Printf("[%v] host: %s, old IP: %s, new IP: %s are same, nothing to do", time.Now().Format(time.RFC3339), item.Host, item.Value, listResp.Request.IP)
			}
			return nil
		}
	}
	return nil
}