#!/usr/bin/env python3

import socket
import sys

if len(sys.argv) != 2:
    raise SystemExit(f"Usage: {sys.argv[0]} <hostname>")

hostname = sys.argv[1]

try:
    primary_name, aliases, addresses = socket.gethostbyname_ex(hostname)
except socket.gaierror as exc:
    raise SystemExit(f"Lookup failed for {hostname}: {exc}")

print(f"Input hostname: {hostname}")
print(f"Canonical hostname: {primary_name}")

if aliases:
    print("Aliases:")
    for alias in aliases:
        print(f"  {alias}")

print("IPv4 addresses:")
for address in addresses:
    print(f"  {address}")