CTF: Ping & get DNS name from a list of IPs saved in a file

ip_to_dns.sh

#!/bin/zsh
#Ping & get DNS name from a list of IPs saved in a file
 
#Prompt the user to enter a file name and its path.
read -p "Enter the IP addresses file name / path:" FILE_PATH_NAME
 
 
function check_host(){
        #if not the IP address value is empty
        if [[ -n $IP_ADDRESS ]]
        then
                ping_cmd=$(nmap -sn $IP_ADDRESS| grep 'Host is up' | cut -d '(' -f 1)
                echo '------------------------------------------------'
                if [[ -z $ping_cmd ]]
                then
                        printf "$IP_ADDRESS is down\n"
                else
                        printf "$IP_ADDRESS is up\n"
                        dns_name
                fi
        fi
}
 
function dns_name(){
        dns_name=$(host $IP_ADDRESS)
        printf "$dns_name\n"
}
 
#Iterate through the IP addresses inside the file
for ip in $(cat $FILE_PATH_NAME)
do
        IP_ADDRESS=$ip
        check_host
done