#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <errno.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <shared_memory_name>\n", argv[0]);
        fprintf(stderr, "Example: %s /my_shared_memory\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    const char *shm_name = argv[1];
    
    printf("Reader: Waiting for shared memory object '%s' to be created...\n", shm_name);
    
    // Open the existing shared memory object
    int fd = shm_open(shm_name, O_RDONLY, S_IRUSR);
    if (fd == -1) {
        perror("shm_open");
        exit(EXIT_FAILURE);
    }

    // Map the shared memory object into the address space
    int *shared_data = mmap(NULL, sizeof(int), PROT_READ, MAP_SHARED, fd, 0);
    if (shared_data == MAP_FAILED) {
        perror("mmap");
        close(fd);
        exit(EXIT_FAILURE);
    }

    // Read the integer from shared memory
    int value_read = *shared_data;
    
    printf("Reader: Read integer %d from shared memory '%s'\n", value_read, shm_name);

    getchar();

    // Clean up
    if (munmap(shared_data, sizeof(int)) == -1) {
        perror("munmap");
    }
    
    close(fd);
    
    printf("Reader: Finished reading from shared memory\n");
    return EXIT_SUCCESS;
}