4_12.c

#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>

int file_pipes[2];
int buffer[1];
pid_t fork_result;
int N = 20;

// Обработчик для родительского процесса, который прочитает, а потом запишет.
void parent_rw(int nsig)
{
    read(file_pipes[0], buffer, sizeof(buffer));
    printf("Parent has read: %s\n", buffer[0]);

    if (buffer[0] >= N)
        exit(EXIT_SUCCESS);
    buffer[0] += 1;
    write(file_pipes[1], buffer, sizeof(buffer));
    printf("Parent has sent data\n");

    kill(fork_result, SIGUSR1);
}


void child_write(int nsig)
{

    read(file_pipes[0], buffer, sizeof(buffer));
    printf("Child has read: %s\n", buffer[0]);
    if (buffer[0] >= N)
        exit(EXIT_SUCCESS);
    buffer[0] += 1;
    write(file_pipes[1], buffer, sizeof(buffer));
    printf("Child has sent data\n");

    kill(getppid(), SIGUSR1);
}


int main()
{
    (void)signal(SIGUSR2, child_write);
    memset(buffer, '0', sizeof(buffer));
    if (pipe(file_pipes) == 0)
    {
        fork_result = fork();
        if (fork_result == -1)
        {
            fprintf(stderr, "Fork failure");
            exit(EXIT_FAILURE);
        }
        if (fork_result == 0)  // child.
            while(1);

        else
        {   // parent
            (void)signal(SIGUSR1, parent_rw);

            buffer[0] = 1;
            write(file_pipes[1], buffer, sizeof(buffer));
            printf("Parent has sent data\n");

            kill(fork_result, SIGUSR2);

            while(1);
        }
    }
    exit(EXIT_SUCCESS);
}