Inter-process communication using pipes |

fork-tasks-demo.c

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <stdlib.h>
#include <linux/limits.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <signal.h>
#include <stdbool.h>

# define PARENT_TO_CHILD 1
# define CHILD_TO_PARENT 0
# define READ_END 0
# define WRITE_END 1

int main() {
    pid_t ppid = getpid();
    int n_process = 20;
    int n_tasks = 10000;
    int n_tasks_per_process = 100;
    if (n_process <= 0 || n_tasks <= 0 || n_tasks_per_process <= 0 || n_tasks * n_tasks_per_process < n_tasks) {
        return 1;
    }
    int fds[n_process][2][2];
    for (int i = 0; i < n_process; i++) {
        pipe(fds[i][CHILD_TO_PARENT]);
        pipe(fds[i][PARENT_TO_CHILD]);
    }

    for (int i = 0; i < n_process; i++) {
        if (fork() == 0) {
            int num = 1;
            while (num != 0) {
                read(fds[i][PARENT_TO_CHILD][READ_END], &num, sizeof(int));

                printf("Child %d: %d\n", i, num);
                int num0 = 0;
                write(fds[i][CHILD_TO_PARENT][WRITE_END], &num0, sizeof(int));
            }
            for (int j = 0; j < 2; j++) {
                for (int k = 0; k < 2; k++) {
                    close(fds[i][j][k]);
                }
            }

        }
    }
    if (ppid == getpid()) {
        int num;
        int num0 = 0;
        for (int i = 1; i <= n_tasks; i++) {
//            printf("Requested process %d to do tasks %d\n",
//                   (i - 1) % (n_process * n_tasks_per_process) / n_tasks_per_process, i);
            write(fds[(i - 1) % (n_process * n_tasks_per_process) / n_tasks_per_process][PARENT_TO_CHILD][WRITE_END],
                  &i,
                  sizeof(int));
            read(fds[(i - 1) % (n_process * n_tasks_per_process) / n_tasks_per_process][CHILD_TO_PARENT][READ_END],
                 &num,
                 sizeof(int));

        }
        for (int i = 0; i < n_process; i++) {
            write(fds[i][PARENT_TO_CHILD][WRITE_END], &num0, sizeof(int));
            read(fds[i][CHILD_TO_PARENT][READ_END], &num, sizeof(int));
            for (int j = 0; j < 2; j++) {
                for (int k = 0; k < 2; k++) {
                    close(fds[i][j][k]);
                }
            }
        }

    }
}