Converter.sh, a bash script to convert domain lists to resolved IP lists without duplicates

converter.sh

#!/bin/bash
# Converter.sh by @xdavidhu
# This is a script inspired by the Bug Hunter's Methodology 3 by @Jhaddix
# With this script, you can convert domain lists to resolved IP lists without duplicates.
# Usage: ./converter.sh [domain-list-file] [output-file]

echo -e "[+] Converter.sh by @xdavidhu\n"
if [ -z "$1" ] || [ -z "$2" ]; then
  echo "[!] Usage: ./converter.sh [domain-list-file] [output-file]"
  exit 1
fi
echo "[+] Resolving domains to IPs..."
while read d || [[ -n $d ]]; do
  ip=$(dig +short $d|grep -oE "\b([0-9]{1,3}\.){3}[0-9]{1,3}\b"|head -1)
  if [ -n "$ip" ]; then
    echo "[+] '$d' => $ip"
    echo $ip >> $2
  else
    echo "[!] '$d' => [RESOLVE ERROR]"
  fi
done < $1
echo -e "\n[+] Removing duplicates..."
sort $2 | uniq > $2.new
mv $2.new $2
echo -e "\n[+] Done, IPs saved to '$2'."

You should create an additional version for IPv6.
Or a version with which IPv6 and IPv4 can be queried at the same time.

IP V6

Code:
/^\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d
\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|
(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|
(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|
(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|
(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|
(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))(%.+)?\s*$/


The regex matches the following IPv6 address forms. Note that these are all the same address:

fe80:0000:0000:0000:0204:61ff:fe9d:f156 // full form of IPv6
fe80:0:0:0:204:61ff:fe9d:f156 // drop leading zeroes
fe80::204:61ff:fe9d:f156 // collapse multiple zeroes to :: in the IPv6 address
fe80:0000:0000:0000:0204:61ff:254.157.241.86 // IPv4 dotted quad at the end
fe80:0:0:0:0204:61ff:254.157.241.86 // drop leading zeroes, IPv4 dotted quad at the end
fe80::204:61ff:254.157.241.86 // dotted quad at the end, multiple zeroes collapsed

In addition, the regular expression matches these IPv6 forms:

::1 // localhost
fe80:: // link-local prefix
2001:: // global unicast prefix

Hey inteligent.
Please create such repo with additional feature like specifying no. of threads, and taking resolvers from .txt file. which would increase the speed of resolve of domain to ip.

Thanks --> Does anyone have tips for recon for finding information disclosure Vulns? thanks