IPtoHOSTNAME

#!/bin/bash

#Written by ProbieK
#https://github.com/ProbieK/

echo "IP list to find Hostnames for: "
read -p ">" USERINPUT

function alivecheck {
                read -r -p "Print only [1]alive hosts or print [*]all hosts? " response
                case $response in
                        1)
                           for IP in $IPLIST; do
                           VAR1=$(sudo arp-scan -q $IP | tail -n +3 | head -n -3 | sed $'s/\t.*//')
                           for VAR in $VAR1; do
                           VARNS=$(nslookup $VAR | tail -n 2 | head -n 1 | sed $'s/^.*= //' | cut -f1 -d ".")
                           echo "$IP: $VARNS"
                           done
                           done;;
                        *)
                           for IP in $IPLIST; do
                           VARNS=$(nslookup $IP | tail -n 2 | head -n 1 | sed $'s/^.*= //' | cut -f1 -d ".")
                           echo "$IP: $VARNS"
                           done;;
                esac
}

if [ -f $USERINPUT ] ; then
	IPLIST=$(<$USERINPUT)
	alivecheck
else
	IPLIST=$(sudo arp-scan -q $USERINPUT | tail -n +3 | head -n -3 | sed $'s/\t.*//')
		for IP in $IPLIST; do
			VARNS=$(nslookup $IP | tail -n 2 | head -n 1 | sed $'s/^.*= //' | cut -f1 -d ".")
			echo "$IP: $VARNS"
		done
fi