3. Write a program by implementing semaphore.

// C program to demonstrate working of Semaphores
#include
#include
#include
#include

sem_t mutex;

void* thread(void* arg)
{
//wait
sem_wait(&mutex);
printf("\nEntered..\n");

//critical section
sleep(4);

//signal
printf("\nJust Exiting...\n");
sem_post(&mutex);
}


int main()
{
sem_init(&mutex, 0, 1);
pthread_t t1,t2;
pthread_create(&t1,NULL,thread,NULL);
sleep(2);
pthread_create(&t2,NULL,thread,NULL);
pthread_join(t1,NULL);
pthread_join(t2,NULL);
sem_destroy(&mutex);
return 0;
}