Python and NGREP

I want to be able to start and stop an NGREP process from inside my python code. I really dont have experience with python on a system level.

Normally I run NGREP from the command line, but I would like to be able to run it from a script every hour and capture the trace and then process the results.

Can anyone point me in the direction of how to achieve this.

By the way, I really just need to be able to do a packet c开发者_Python百科apture, perhaps Python has builtin capabilities for this, maybe tcpdump?

Thanks.

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I am not an expert but I would do this:

import subprocess
import sys
import re
import time

keep_running = 1 #Loop flag
wait_hours = 12  #Stop for 12 hours and then run again
run_hours = 1    #We will run ngrep for an hour. The nth run will be dumped to net_log_n.txt
f_num=0
hours_so_far=0
run_time_limit = 100    #Suppose you only want to take a log for 100 hours while you are away.
while keep_running:
    ngrep_cmd = "sudo ngrep -ixW >  net_log_" + str(fnum) + ".txt &"
    subprocess.call([ngrep_cmd], shell=True)
    time.sleep(run_hours*3600)
    subprocess.call(["sudo killall ngrep"], shell=True)
    time.sleep(wait_hours*3600)
    f_num += 1
    hours_so_far += run_hours
    if hours_so_far >= run_time_limit:
        keep_running = 0

You will have to run it as root or with sudo.

I hope it helps!

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its not in-built, but you can try Packet Capture and Injection Library

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Look up threading.Timer and pexpect. If you don't want to install pexpect, you can use subprocess.Popen instead.

EDIT: In response to the comment:

import os
from signal import SIGTERM, SIGKILL
os.kill(pid, SIGTERM) #you can also send SIGKILL instead of SIGTERM. 
#You might also have to put this call in a try block and catch OSError
#Only available on *NIX

EDIT2: If you want to hand-roll the packet capture, use pypcap. This should almost certainly do what you want, since tcpdump uses libpcap itself.