Shell Programming and Scripting

server1    x.x.x.x
server2    x.x.x.x
server3    x.x.x.x
server4    x.x.x.x
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man nslookup

while read SERVER
do
 ssh -q $SERVER "$COMMAND" | <further processing of the output if required> >> output.txt
done < hostname.lst

user1 server1
user2 server2

while read USERNAME SERVER
do
 ssh -q ${USERNAME}@$SERVER "$COMMAND" | <further processing of the output if required> >> output.txt
done < hostname.lst

for SERVER in `cat server-list`
do
ping -c 1 $SERVER | awk '{ print $2"\t"$3 }' | head -n 1 | tr -d '()'
done

dig -f hostsfile.txt +noall +answer | awk '{print $1, $NF}'