Shared mem GPT

#include <iostream>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <unistd.h>
#include <cstdlib>
#include <cstring>
#include <sys/wait.h>

int main() {
    // Key to identify the shared memory segment
    key_t key = ftok("/tmp", 'S'); // You may use any valid path and id

    // Size of the shared memory segment
    size_t size = sizeof(int);

    // Create a shared memory segment
    int shmid = shmget(key, size, IPC_CREAT | 0666);
    if (shmid == -1) {
        perror("shmget");
        exit(1);
    }

    // Attach to the shared memory segment
    int *shared_memory = (int *)shmat(shmid, NULL, 0);
    if (shared_memory == (int *)(-1)) {
        perror("shmat");
        exit(1);
    }

    // Parent process writes to shared memory
    *shared_memory = 42;

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

    if (pid < 0) {
        perror("fork");
        exit(1);
    } else if (pid == 0) {
        // Child process reads from shared memory
        std::cout << "Child Process: Value read from shared memory: " << *shared_memory << std::endl;
        exit(0);
    } else {
        // Parent process waits for child to finish
        wait(NULL);

        // Detach from the shared memory segment
        if (shmdt(shared_memory) == -1) {
            perror("shmdt");
            exit(1);
        }

        // Remove the shared memory segment (optional)
        if (shmctl(shmid, IPC_RMID, NULL) == -1) {
            perror("shmctl");
            exit(1);
        }
    }

    return 0;
}