Shell script to look up DNS registers and catch up IPs being populated in /etc/hosts

dns-scraper.sh

#!/bin/bash

labserver_list=(
  host1.mylabserver.com
  host2.mylabserver.com
  host3.mylabserver.com
)

echo "Backing Up Hosts..."
sudo cp -p /etc/hosts /etc/hosts.save

temp_hosts=$(mktemp)

count=1

for host in "${labserver_list[@]}"; do
  ip=$(dig @1.0.0.1 +short "$host" -4 -t A +time=5)

  # Check if dig returned a valid IP address
  if [[ -n "$ip" ]]; then
    echo -e "$ip \t acg-0$count \t k$count \t $host" >> "$temp_hosts"
    echo "Added $ip  acg-0$count to temporary hosts file"
  else
    echo "Failed to resolve IP for $host (timeout or other error)"
  fi

  ((count++))
done

if [ -s "$temp_hosts" ]; then
  # Remove existing entries and add new ones
  sudo awk '
    NR==FNR {
      new_entries[$NF] = $0;
      next
    }
    $NF in new_entries {
      print new_entries[$NF];
      delete new_entries[$NF];
      next
    }
    {print}
    END {
      for (entry in new_entries) {
        print new_entries[entry]
      }
    }
  ' "$temp_hosts" /etc/hosts > /tmp/hosts.new

  sudo mv /tmp/hosts.new /etc/hosts
fi

rm -f "$temp_hosts"