server.c

#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <semaphore.h>
#include <fcntl.h>
#include <sys/stat.h>

#define BUF_SIZE 512

const char* read_sem_name = "read_semaphore";
const char* write_sem_name = "write_semaphore";
const char* child_name = "/home/zakhar/Documents/C/Pipe/Client";

sem_t* open_sem(const char* sem_name, unsigned int value)
{
    sem_t* sem = sem_open(sem_name, O_CREAT, S_IRWXO | S_IRWXU, value); // other processes have write and read permission
    if (sem == SEM_FAILED)
    {
        fprintf(stderr, "Can't create a semaphore\n");
        return NULL;
    }

    return sem;
}

int main(int argc, char** argv)
{
    sem_t* read_sem = open_sem(read_sem_name, 0);
    sem_t* write_sem = open_sem(write_sem_name, 1);

    int pipefd[2];

    if (pipe(pipefd) == -1)
    {
        fprintf(stderr, "Can't make a pipe\n");
        exit(EXIT_FAILURE);
    }

    char string[BUF_SIZE];

    char** args = malloc(sizeof(char*) * 2);
    args[0] = malloc(sizeof(char) * (strlen(child_name) + 1));
    strncpy(args[0], child_name, strlen(child_name) + 1);
    args[1] = NULL;

    pid_t pid = fork();
    if (pid == -1)
    {
        fprintf(stderr, "Can't create a child process\n");
        close(pipefd[1]);
        close(pipefd[0]);
        sem_close(read_sem);
        sem_close(write_sem);
        sem_unlink(write_sem_name);
        sem_unlink(read_sem_name);
        exit(EXIT_FAILURE);
    }
    else
    {
        if (pid == 0)
        {
            close(pipefd[1]);
            if (dup2(pipefd[0], 0) == -1)
            {
                fprintf(stderr, "Failed to dup read end\n");
                exit(EXIT_FAILURE);
            }
            close(pipefd[0]);

            if (execvp(child_name, args) == -1)
            {
                fprintf(stderr, "Execvp error!\n");
                exit(EXIT_FAILURE);
            }
        }
    }

    close(pipefd[0]);

    while (1)
    {
        sem_wait(write_sem);

        fgets(string, BUF_SIZE, stdin);
        if (*string == '\0' || *string == '\n' || *string == '\r')
        {
            kill(pid, SIGTERM);
            break;
        }

        write(pipefd[1], string, BUF_SIZE);
        sem_post(read_sem);
    }

    close(pipefd[1]);
    sem_close(read_sem);
    sem_close(write_sem);
    sem_unlink(write_sem_name);
    sem_unlink(read_sem_name);

    free(args[0]);
    free(args);

    exit(EXIT_SUCCESS);
}