Question

In c++ how would you alternate running between programs ran at the same time ran like program1 & program1 using semaphores? The first program would cout something followed by the second program cout something.

Answer 1

// C program to demonstrate working of Semaphores 
#include <stdio.h> 
#include <pthread.h> 
#include <semaphore.h> 
#include <unistd.h> 

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; 
}