Bash: pinging servers and writing the IP to a file

Question

I currently have to find the IP-Adresses of a lot of servers.

I have written a bash script on linux that creates all the server names.

When I write it like this, I get all servernames, even if there no longer have an IP.

host $f$n$d >> IPs.txt

Is there a way to only write the servers into the file, that still have an IP, together with the servername.

Kind regards Elias

You probably can work-up something with `dig`, see https://serverfault.com/q/372066/154366 — Fravadona, Mar 14 '22 at 11:59
```$f$n$d``` is the declaration of the IP-adress I have to ping. — , Mar 14 '22 at 13:44
OK, so your problem would be: You have a bunch of IP-addresses and you want to check if they still have an associated `PTR Record` in the DNS server? — Fravadona, Mar 14 '22 at 15:39

score 0 · Answer 1 · answered Mar 14 '22 at 09:18

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I think the local DNS resolver caches the IP addresses, so you will get the corresponding IPs even in the scenario you described.

I suggest you to start the script with a full local DNS flush, depending on your distribution and DNS client: Here are son techinques to flush it.

answered Mar 14 '22 at 09:18

Antonio Petricca

This will sadly not work, because those IPs where created as "support-IPs" for servers, and when these servers where removed those IPs where left over. I also have to operate from a server with this script, on which I am probably not allowed to do such things... – Mar 14 '22 at 09:40
1

I understand. I suggest you to post this questo on **UnixStackExchange** for a better support. – Antonio Petricca Mar 14 '22 at 09:43

1 Answers1