#include <stdio.h>

#include <unistd.h>

#include <fcntl.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <sys/time.h>

#include <sys/ipc.h>

#include <sys/shm.h>

#include <pthread.h>

#include <semaphore.h>



int main(int argc, char *argv[]) {

    struct timeval tv1, tv2;

    gettimeofday(&tv1, NULL);

    int i;

    sem_t *sem;



    key_t shmkey = ftok("./3.c", 24);// change this pathname to whatever you name this file when you save it

    int shmid = shmget(shmkey, sizeof(sem_t), 0644|IPC_CREAT);

    if (shmid == -1) {

      perror("Error creating shared memory");

      exit(1);

    }

    sem = (sem_t*) shmat(shmid, NULL, 0);

    sem_init(sem, 1, 5);



    for (i = 0; i < 10; i++) {

        int f = fork();

        if (f < 0) {

            perror("Oh no! Anyway...");

        } else if (f == 0) {

            sem_wait(sem);

            sleep(1);

            sem_post(sem);

            exit(0);

        }

    }



    for (i = 0; i < 10; i++) {

        wait(0);

    }

    sem_destroy(sem);

    shmdt(sem);

    shmctl(shmid, IPC_RMID, 0);

    gettimeofday(&tv2, NULL);

    printf("Total time = %f seconds\n", (double)(tv2.tv_usec - tv1.tv_usec) / 1000000 + (double) (tv2.tv_sec - tv1.tv_sec));



    return 0;

}