Cheatsheet - Python subprocess communication Link to heading

Imports Link to heading

from subprocess import Popen, PIPE

Imports for signals Link to heading

import signal, os

Start process Link to heading

process = Popen(['./sum 50'], shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE)

Check if process is alive Link to heading

def isAlive(process):
	poll = process.poll()
	if poll == None:
		print("Program running...")
	else:
		print("Program stopped :(")

Read from stdout Link to heading

def getline(process):
	return "stdout : " + process.stdout.readline().decode('utf-8')

Write to stdin Link to heading

process.stdin.write((str(i)+"\n").encode())
process.stdin.flush()

Send signals Link to heading

os.kill(process.pid, signal.SIGSTOP)

Available signals :

{.table .pure-table .table-striped .table-responsive}

Full code example Link to heading

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv){
	
	int sum, tmp, i;

	sum = atoi(argv[1]);
	printf("initial sum :%d\n", sum);

	for(i=0;i<5;i++){
		printf("Nb :\n");
		fflush(stdout);
		scanf("%d",&tmp);
		sum += tmp ;
	}

	printf("\nSum : %d", sum);
	return 0 ;
}

#!/usr/bin/env python3
from subprocess import Popen, PIPE
import signal, os

def isAlive(process):
	poll = process.poll()
	if poll == None:
		print("Program running...")
	else:
		print("Program stopped :(")

def getline(process):
	return "stdout : " + process.stdout.readline().decode('utf-8')


process = Popen(['./sum 50'], shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE)

print(getline(process))

for i in range(1,6):
	print(getline(process))
	print("write " + str(i))
	process.stdin.write((str(i)+"\n").encode())
	process.stdin.flush()

	
print(getline(process))
print(getline(process))
		

#Stop/resume process
# os.kill(process.pid, signal.SIGSTOP)
#os.kill(process.pid, signal.SIGCONT)