nslookup:只返回IP地址

Question

我的研究表明，nslookup从未真正用于脚本使用:使用dig代替，使用+short选项根据查询参数生成机器可读的输出。

dig +short myip.opendns.com @resolver1.opendns.com

尽管如此，我的路由器不支持dig，也不支持nslookup。我试图将返回的IP地址保存为一个变量，以便与实际IP地址进行比较：

ip=$(curl -沉默http://api.ipify.org/)

awk在Ubuntu上取得了成功：

nslookup yahoo.com  | awk -F': ' 'NR==6 { print $2 } '

但是返回了DD-WRT路由器上的一个错误：

nslookup: can't resolve '(null)'
2001:4998:58:1836::10 media-router-fp1.prod1.media.vip.bf1.yahoo.com

最终目标

我有CLI .sh命令来更新DDNS服务:每当测量和存储的DDNS地址不同时，我想执行update命令(CRON作业每5分钟检查一次)。

问题

什么是最简单的nslookup，相当于上面提到的dig示例？

观测、反馈和测试区域

第二个论点补充说：

root@DD-WRT:/opt# nslookup mydomain.asuscomm.com  resolver1.opendns.com
Server:    208.67.222.222
Address 1: 208.67.222.222 resolver1.opendns.com

Name:      mydomain.asuscomm.com
Address 1: 7W.10X.7Y.6Z c-7W-10X-7Y-6Z.hsd1.fl.comcast.net

devnull：> /dev/null

root@DD-WRT:/opt# nslookup mydomain.asuscomm.com  > /dev/null
nslookup: can't resolve '(null)'

devnull：> /dev/null 2>&1

root@DD-WRT:/opt# nslookup mydomain.asuscomm.com  > /dev/null 2>&1
root@DD-WRT:/opt# 

输入nslookup：

root@DD-WRT:~# type nslookup
nslookup is /usr/bin/nslookup

管道到grep，然后归档：

root@DD-WRT:/opt# nslookup myDomain.asuscomm.com | grep Address > test.txt
nslookup: can't resolve '(null)'
root@DD-WRT:/opt# cat test.txt
Address 1: 7W.10X.7Y.6Z c-7W-10X-7Y-6Z.hsd1.fl.comcast.net

nslookup

root@DD-WRT:/opt/test# nslookup myFQDN.asuscomm.com

Name:      mydomain.asuscomm.com
Address 1: 7x.10x.7.x6x c-7x-10x-7x-6x.hsd1.fl.comcast.net

查找雅虎

root@DD-WRT:/opt# nslookup yahoo.com

nslookup: can't resolve '(null)'

Name:      yahoo.com
Address 1: 2001:4998:c:1023::5 media-router-fp2.prod1.media.vip.gq1.yahoo.com
Address 2: 2001:4998:58:1836::10 media-router-fp1.prod1.media.vip.bf1.yahoo.com
Address 3: 2001:4998:58:1836::11 media-router-fp2.prod1.media.vip.bf1.yahoo.com
Address 4: 2001:4998:c:1023::4 media-router-fp1.prod1.media.vip.gq1.yahoo.com
Address 5: 2001:4998:44:41d::3 media-router-fp1.prod1.media.vip.ne1.yahoo.com
Address 6: 2001:4998:44:41d::4 media-router-fp2.prod1.media.vip.ne1.yahoo.com
Address 7: 72.30.35.9 media-router-fp1.prod1.media.vip.bf1.yahoo.com
Address 8: 98.137.246.7 media-router-fp1.prod1.media.vip.gq1.yahoo.com
Address 9: 98.138.219.231 media-router-fp1.prod1.media.vip.ne1.yahoo.com
Address 10: 98.138.219.232 media-router-fp2.prod1.media.vip.ne1.yahoo.com
Address 11: 72.30.35.10 media-router-fp2.prod1.media.vip.bf1.yahoo.com
Address 12: 98.137.246.8 media-router-fp2.prod1.media.vip.gq1.yahoo.com

grep：

root@DD-WRT:/# nslookup yahoo.com | grep gq1


nslookup: can't resolve '(null)'
Address 1: 2001:4998:c:1023::4 media-router-fp1.prod1.media.vip.gq1.yahoo.com
Address 6: 2001:4998:c:1023::5 media-router-fp2.prod1.media.vip.gq1.yahoo.com
Address 7: 98.137.246.8 media-router-fp2.prod1.media.vip.gq1.yahoo.com
Address 8: 98.137.246.7 media-router-fp1.prod1.media.vip.gq1.yahoo.com

grep：

root@DD-WRT:/opt# nslookup yahoo.com | grep -o -E '([0-9][0-9]?[0-9]?\.?){4}grep3：root@DD-WRT:/opt# nslookup mydomain.asuscomm.com | grep -o -E '([0-9][^:][0-9]?[0-9]?\.?){4}' > output.txt
nslookup: can't resolve '(null)'
root@DD-WRT:/opt# cat output.txt
7W.10X.7Y.6Z
W-10X-7Y-6Z.

nslookup: can't resolve '(null)'

grep3：

A25

Answer 1

这样做是可行的：

nslookup "$D" 2>/dev/null  | grep "Address " | sed 's/.*: //g;s/ .*//g'

但请注意

• 它可以返回多个地址，因此可以遍历它们。
• 如果你不想要的话，可以退出ipv6
• 许多域解决了每个查询都不同的问题(比如amazon随机使用cloudfront、fastly或其他ips )