Basic nslookup loops for Windows and Linux

nslookup loops

*****WINDOWS*****

//nslookup - subnet range
c:\>for /L %i in (1,1,255) do @nslookup 10.10.10.%i [server to resolve from] 2>nul | find "Name" && echo 10.10.10.%i && @echo [ctrl+g]

//nslookup - file of ip's
NAME c:\>for /F %i in ([file.txt]) do @nslookup %i [server to resolve from] 2>nul | find "Name" && echo %i
ADDRESS c:\>for /F %i in ([file.txt]) do @nslookup %i [server to resolve from] 2>nul | find "Address" && echo %i 

Or just run c:\>nslookup and paste in the list
This does not have as clean of output as the for loop though

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*****LINUX*****

#script
#!/bin/sh
for IP in `cat ./ips.txt`
do
  printf "$IP\t"
	LOOKUP_RES=`nslookup $IP`
	FAIL_COUNT=`echo $LOOKUP_RES | grep "** server can't find " | wc -l`;
	if [ $FAIL_COUNT -eq 1 ]
	then
		NAME='Bad FQDNS\n';
	else
		NAME=`echo $LOOKUP_RES | grep -v nameserver | cut -f 2 | grep name | cut -f 2 -d "=" | sed 's/ //'`;
	fi
	echo $NAME
done

# one-liner
$ for i in `cat urls.txt`; do nslookup $i 2>/dev/null | grep Address | tail -n 1 | cut -d " " -f 3; done > ips.txt

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So if you want to go the other way - you have DNS names but you want IPs, I worked off yours and came up with:

#script
#!/bin/sh
for DNAME in `cat urls.txt`
do
  printf "$DNAME "
	LOOKUP_RES=`nslookup $DNAME`

	FAIL_COUNT=`echo $LOOKUP_RES | grep "Can't find" | wc -l`;

	if [ $FAIL_COUNT -eq 1 ]
	then
		NAME='Not in DNS';
	else
		NAME=`echo $LOOKUP_RES | grep Address: | tail -1 | cut -c 9-30`;
	fi
	echo $NAME
done

Technically I only tested it on Mac, but should work the same on linux/bash.

nice! Been a while since I've looked at this gist, but glad to see it's still useful. :-)

@daretogo
You should put the $LOOKUP_RES in double quotes, otherwise line breaks will not be kept and everything will end up as one line, hence tail -1 will grab the first occurrence which would be the nameserver rather than the response.