Python Script to Retrieve Domain SSL Certificate Expiration Date and Remaining Days

This article provides a Python script that obtains a domain name, executes a curl command to fetch SSL certificate details, parses the start and expiration dates, converts them to datetime objects, and calculates the remaining days until expiration.

The script imports necessary modules, defines a main(domain) function, uses subprocess.getstatusoutput to run curl -Ivs https://{domain} --connect-timeout 10 , captures the output, and extracts fields with a regular expression.

It then converts the extracted date strings using time.strptime and datetime.strptime , formats them, computes the difference between the expiration date and the current time, and returns the number of days remaining.

When run as a script, it reads the domain from command‑line arguments, calls main , and prints the remaining days.

import re
import sys
import time
import subprocess
from datetime import datetime
from io import StringIO

def main(domain):
    f = StringIO()
    comm = f"curl -Ivs https://{domain} --connect-timeout 10"
    result = subprocess.getstatusoutput(comm)
    f.write(result[1])
    try:
        m = re.search('start date: (.*?)\n.*?expire date: (.*?)\n.*?common name:(.*?)\n.*?issuer: CN=(.*?)\n', f.getvalue(), re.S)
        start_date = m.group(1)
        expire_date = m.group(2)
        common_name = m.group(3)
        issuer = m.group(4)
    except Exception as e:
        return 999999999
    start_date = time.strptime(start_date, "%b %d %H:%M:%S %Y GMT")
    start_date_st = time.strftime("%Y-%m-%d %H:%M:%S", start_date)
    expire_date = datetime.strptime(expire_date, "%b %d %H:%M:%S %Y GMT")
    expire_date_st = datetime.strftime(expire_date, "%Y-%m-%d %H:%M:%S")
    remaining = (expire_date - datetime.now()).days
    return remaining

if __name__ == "__main__":
    domain = sys.argv[1]
    remaining_days = main(domain)
    print(remaining_days)