自动检测公网IP地址并更新到公云PubYun

## 操作说明

1、保存内容到文件`ddnsUpdate.sh`
2、修改如下配置为自己实际信息，其中:
`Udomain`为主机名
`loginUser`为登录用户名
`loginPassword`为登录密码
3、保存后执行`nohup bash ./ddnsUpdate.sh &`命令即可
------------
注意：
1、需要先安装curl程序，在centos下安装的命令为：`yum install curl -y`
2、该脚本已实现自运行监测，只需要添加该脚本到定时任务并让其每分钟执行一次即可。(原理为每分钟检查一次脚本是否在运行，已运行则退出，未运行则启动新的脚本循环任务每秒检查一次)

## 脚本源码
```shell
#!/bin/bash

ddnsDomain=' '
loginUser=' '
loginPassword=' '

#IP检测地址
checkIp='http://ip1.dynupdate.no-ip.com'

DIR="$( cd "$( dirname "$0"  )" && pwd  )"
#检查是否已执行该程序
processNum=$(ps -aux|grep ddnsUpdatePlus.sh|grep -v grep|wc -l)
if [[ "$processNum" < '3' ]]; then
    nohup  bash $DIR/ddnsUpdatePlus.sh &
    rm -f $DIR/nohup.out
else
        exit 0
fi

function dateInfo() {
	echo "[$(date +%F\ %H:%M:%S)] "
}

while true; do
		#date="[$(date +%F\ %H:%M:%S)] "
		retCode='000'
		while [[ $retCode == '000' ]]; do
			retCode=`curl -I -s --connect-timeout 5 www.baidu.com -w %{http_code} | tail -n1`
			sleep 1
			if [[ $retCode == '000' ]]; then
				echo "`dateInfo` Network connectivity check failed, retrying..."  >> $DIR/ipUpdate.log
			fi
		done
        #如果文件不存在，就自动创建信息
        if [[ ! -f /root/.currPublicIP ]]; then echo "$(curl -s $checkIp)" > /root/.currPublicIP; fi
        #获取新公网ip
        new_ip=`curl -s $checkIp`
        while [[ $new_ip == '' ]]; do
        	echo "`dateInfo` Failed to obtain the new ip address and try again after 1 sec..."  >> $DIR/ipUpdate.log
        	sleep 1
    		new_ip=`curl -s $checkIp`
    		if [[ $new_ip != '' ]]; then echo "`dateInfo` Success to obtain the new ip address"  >> $DIR/ipUpdate.log;fi
    	done
        #查看旧ip
        old_ip=`cat /root/.currPublicIP`

domainIP=$old_ip
        #当旧ip不同于新ip则更新信息
        while [[ $domainIP != $new_ip ]]; do
                #更新信息到公云
                echo "`dateInfo` Update forced for alias $ddnsDomain, new IP -> $new_ip" >> $DIR/ipUpdate.log
                Msg=$(/usr/bin/curl -s -u $loginUser:$loginPassword "http://members.3322.net/dyndns/update?system=dyndns&hostname=$ddnsDomain")
                echo "`dateInfo` Return result: $Msg" >> $DIR/ipUpdate.log
                #休息3秒后查域名解析状态
                sleep 3
                domainIP=$(ping $ddnsDomain -c 1 | sed '1{s/[^(]*(//;s/).*//;q}')
                if [[ $domainIP == $new_ip ]]; then
                        echo "`dateInfo` Successful alias table update for $ddnsDomain." >> $DIR/ipUpdate.log
                fi
        done
        echo $domainIP > /root/.currPublicIP
        #休息1秒再检查
        sleep 1
done
```