Script required to find duplicate hostname resolve with DNS

Script required to find duplicate hostname resolve with DNS
        In our build environment we want find Duplicate hostname entry against all. We need a script which will run following logic

1.get IPs from file
2. run nslookup <ipaddress1> - it will give hostname1  (it will give only one hostname)
 then again  I need  to type same Ip again to get second hostname.(dublicate hostname)
 nslookup <ipaddress1> it will give hostname2 ( In this example hostname1 and hostname2 pointing to same IP)

So what i need is  nslookup <ipaddress> part need to run two times one after another continuously and outputs need to be compared. If output hostnames differs it need to be pasted as duplicate hostname entry for that IP. if it hostname didn't vary the output don't need to be reported.
        help please.
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rammaghentharAsked:
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omarfaridCommented:
do you own / manage the dns server for the reverse lookup zone? if yes , then you can do simple

grep ipaddress zonefile

to find duplicates
0
woolmilkporcCommented:
OK,

and if not, here is the script.

Good luck!

wmp






#!/bin/ksh
 
iplist=/file/containing/ipaddresses
result=/file/containing/result
errors=/file/conatining/errors
 
rm $result 2>/dev/null
rm $errors 2>/dev/null
 
while read -r ip
  do
    host1=$(nslookup "$ip" 2>>$errors | tail +3 | grep "Name:" | awk '{print $2}')
    host2=$(nslookup "$ip" 2>>$errors | tail +3 | grep "Name:" | awk '{print $2}')
    [ ${host1}x = "x" -o ${host2}x = "x" ] && continue
    [ $host1 != $host2 ] && echo "$ip resolves to $host1 AND $host2" >> $result
  done < $iplist
exit

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