replaces all occurences of a specified mac address in a pcap file with a random new one

mac_replacer.py

import sys, os

def usage():
	print "usage: %s file.pcap AA:BB:CC:DD:EE:FF"%sys.argv[0]
	print "where AA:BB:CC:DD:EE:FF is the mac address you want replaced"
	sys.exit(1)

if len(sys.argv) < 3: usage()

file_arg = sys.argv[1]
mac_arg = sys.argv[2]
mac = mac_arg.replace(':', '').decode('hex')
assert(len(mac) == 6)
new_mac = os.urandom(6)

with open(file_arg, "r") as h: fc = h.read()

with open(file_arg, "w") as h: h.write(fc.replace(mac, new_mac))