如何通过分析URL来检测子域？

nslookup -type=NS example.com

sublist3r -d example.com -t 100 -w wordlist.txt -o output.txt

import dns.resolver
import requests

def find_subdomains(domain):
    subdomains = set()
    try:
        answers = dns.resolver.resolve(domain, 'NS')
        for rdata in answers:
            subdomain = str(rdata).split('.')[0]
            if subdomain != domain:
                subdomains.add(subdomain)
    except dns.resolver.NXDOMAIN:
        print(f"{domain} does not exist.")
    except dns.resolver.NoAnswer:
        print(f"{domain} has no NS records.")
    except dns.resolver.Timeout:
        print(f"Timed out while querying {domain}.")
    
    return subdomains

def check_subdomain(subdomain):
    try:
        response = requests.get(f"http://{subdomain}")
        if response.status_code == 200:
            print(f"{subdomain} is active.")
        else:
            print(f"{subdomain} is not active or returns status code {response.status_code}.")
    except requests.exceptions.RequestException as e:
        print(f"Error checking {subdomain}: {e}")

if __name__ == "__main__":
    domain = "example.com"
    subdomains = find_subdomains(domain)
    for subdomain in subdomains:
        check_subdomain(f"{subdomain}.{domain}")