semaphore.c

#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>

void * read(void * arg);
void * accu(void * arg);
static sem_t sem_one;
static sem_t sem_two;
static int num;

int main(int argc, char const *argv[])
{
	pthread_t id_t1, id_t2;
	sem_init(&sem_one, 0, 0);
	sem_init(&sem_two, 0, 1);

	pthread_create(&id_t1, NULL, read, NULL);
	pthread_create(&id_t2, NULL, accu, NULL);

	pthread_join(id_t1, NULL);
	pthread_join(id_t2, NULL);

	sem_destroy(&sem_one);
	sem_destroy(&sem_two);

	return 0;
}

void * read(void * arg)
{
	int i;
	for (i = 0; i < 5; ++i)
	{
		fputs("Input num: ",stdout);
		sem_wait(&sem_two);
		scanf("%d", &num);
		sem_post(&sem_one);
	}
	return NULL;
}

void * accu(void * arg)
{
	int i,sum=0;
	for (i = 0; i < 5; ++i)
	{
		sem_wait(&sem_one);
		sum+=num;
		sem_post(&sem_two);
		// printf("Result:%d\n", sum);
	}
	printf("Result:%d\n", sum);
	return NULL;
}