Mutex.cpp

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <pthread.h>

typedef struct {
    pthread_mutex_t mutex;
    char data[100];
} SharedMemory;

int main() {
    int shm_fd;
    SharedMemory *shared_memory;

    // Create the shared memory object
    shm_fd = shm_open("my_shm", O_CREAT | O_RDWR, 0666);
    if (shm_fd == -1) {
        perror("Failed to create shared memory");
        exit(EXIT_FAILURE);
    }

    // Configure the size of the shared memory object
    ftruncate(shm_fd, sizeof(SharedMemory));

    // Map the shared memory object
    shared_memory = (SharedMemory *) mmap(NULL, sizeof(SharedMemory), PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
    if (shared_memory == MAP_FAILED) {
        perror("Failed to map shared memory");
        exit(EXIT_FAILURE);
    }

    // Initialize the mutex
    pthread_mutexattr_t attr;
    pthread_mutexattr_init(&attr);
    pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
    pthread_mutex_init(&shared_memory->mutex, &attr);

    // Fork a process
    pid_t pid = fork();

    if (pid < 0) {
        perror("Fork failed");
        exit(EXIT_FAILURE);
    }

    if (pid == 0) { // Child (Consumer)
        for (int i = 0; i < 5; i++) {
            pthread_mutex_lock(&shared_memory->mutex);
            printf("Consumer read: %s\n", shared_memory->data);
            pthread_mutex_unlock(&shared_memory->mutex);
            sleep(1);
        }
    } else { // Parent (Producer)
        for (int i = 0; i < 5; i++) {
            pthread_mutex_lock(&shared_memory->mutex);
            snprintf(shared_memory->data, sizeof(shared_memory->data), "Data %d", i + 1);
            printf("Producer wrote: %s\n", shared_memory->data);
            pthread_mutex_unlock(&shared_memory->mutex);
            sleep(1);
        }
    }

    // Cleanup
    pthread_mutex_destroy(&shared_memory->mutex);
    munmap(shared_memory, sizeof(SharedMemory));
    close(shm_fd);
    shm_unlink("my_shm");

    return 0;
}