Send SIGINT in python to os.system

Question

I am trying to run a Linux command strace -c ./client in python with os.system(). When I press Ctrl + C I get some output on the terminal. I have to send the "Process correctly halted" signal programmatically after one minute and want the terminal output that is produced after pressing Ctrl + C in a file. A pseudo script will be really helpful. If I use subprocess.Popen and then send Ctrl + C signal from keyboard I didn't get output on the terminal,so have to use os.system

Answer 1

In Python, you could programatically send a Ctrl + C signal using os.kill. Problem is, you need the pid of the process that'll receive the signal, and os.system does not tell you anything about that. You should use subprocess for that. I don't quite get what you said about not getting the output on the terminal.

Anyways, here's how you could do it:

import subprocess
import signal
import os

devnull = open('/dev/null', 'w')
p = subprocess.Popen(["./main"], stdout=devnull, shell=False)

# Get the process id
pid = p.pid
os.kill(pid, signal.SIGINT)

if not p.poll():
    print("Process correctly halted")

Answer 2

I would recommend subprocess python module for running linux commands. In that, SIGINT signal (equivalent to Ctrl + C keyboard interrupt) can be sent programmatically to a command using Popen.send_signal(signal.SIGINT) function. Popen.communicate() function will give you output. For example

import subprocess
import signal

..
process = subprocess.Popen(..)  # pass cmd and args to the function
..
process.send_signal(signal.SIGINT)  # send Ctrl-C signal
..
stdout, stderr = process.communicate()  # get command output and error
..