Get the SSL certificate expiration period using timedelta

$ ./cert_expires.py example.com google.com
example.com: 1093 days
google.com: 76 days

#!/usr/bin/env python
thanks: http://qiita.com/uemura/items/a3a0937f77494e62213c
import sys
import re
import subprocess
import datetime
def parse_result_date_string(date_string):
"""
convert date string to datetime
>>> date_string = "Feb  2 05:47:50 2015 GMT"
>>> d = parse_result_date_string(date_string)
>>> d
datetime.datetime(2015, 2, 2, 5, 47, 50)
"""
d = datetime.datetime.strptime(date_string, '%b %d %H:%M:%S %Y %Z')
return d
re_start = re.compile(r'Not Before: (.+)')
re_end = re.compile(r'Not After : (.+)')
def get_date_strings_from_result(result):
"""
:return: cert start date, cert expire date
>>> text = "Not Before: Feb  2 05:47:47 2015 GMT\n" \
...        "Not After : Feb  4 16:03:29 2016 GMT"
>>> get_date_strings_from_result(text)
('Feb  2 05:47:47 2015 GMT', 'Feb  4 16:03:29 2016 GMT')
"""
rr_start = re_start.search(result)
rr_end = re_end.search(result)
return rr_start.group(1) if rr_start else None, 

rr_end.group(1) if rr_end else None
def get_cert_start_expire_date(domain):
"""
:return: cert start date, cert expire date
"""
command = "openssl s_client -connect {}:443 < /dev/null " 

"2> /dev/null | openssl x509 -text | grep Not"
command = command.format(domain)
out = subprocess.check_output(command, shell=True)
ss, es = get_date_strings_from_result(out)
return parse_result_date_string(ss), parse_result_date_string(es)

def get_cert_expire_delta(domain):
"""
time delta cert expire date and now
"""
start_date, expire_date = get_cert_start_expire_date(domain)
return expire_date - datetime.datetime.now()
def main():
for domain in sys.argv[1:]:
delta = get_cert_expire_delta(domain)
print('{}: {} days'.format(domain, delta.days))
if name == 'main':
main()

Reference: http://qiita.com/uemura/items/a3a0937f77494e62213c