print DHCP leases ip and mac pair that are not expire

dhcp_mac_ip.py

#!/usr/bin/env python
# coding: UTF-8
import re
import time

DHCPD_LEASES_FILE="/var/lib/dhcpd/dhcpd.leases"

# read dhcpd_leases file and match all ip,mac pair, and convert to dict type to store
dhcp_leases = open(DHCPD_LEASES_FILE,"r").read()

regex = re.compile('''lease\s
        (?P<ip>\S+)              # The IP
        \s{.*?ends\s\d+\s
        (?P<ends>[0-9:\s/]+);    # lease ends
        .*?hardware\sethernet\s*
        (?P<mac>[a-z0-9:]+)      # request MAC
        .*?}''',re.DOTALL|re.X)

all_oob = regex.findall(dhcp_leases)
valid_date = lambda dhcp_lease_time: time.strptime(dhcp_lease_time,'%Y/%m/%d %H:%M:%S') > time.gmtime() # lease db use gmt time.
oob_dict = dict([[i[2],i[0]] for i in all_oob if valid_date(i[1])]) # oob_dict: { mac => IP }


def main():
  for mac in oob_dict:
    print oob_dict[mac],mac


if __name__ == "__main__":
  main()