生產者，消費者實例（信號量，緩存區）

#include<stdio.h>
#include<stdlib.h>
#include<pthread.h>
#include<semaphore.h>
#include<string.h>
#include<time.h>
#define BUFFERSIZE 5
struct msg
{
    time_t timep;
    int id;
    int pidid;
};
int in;
int out;
int count=0;
int m;
sem_t sem;

struct msg stack[BUFFERSIZE+1],nextP,nextC;

int ran_time()
{
    int j;
    j=1+(int)(5.0*rand()/(RAND_MAX+1.0));
    return j;
}

void producer(void)
{
    int i=0;
    while(i&lt;10)
    {
        sleep(ran_time());
        while((in+1)%BUFFERSIZE==out);       
        sem_wait(&sem);
        time(&nextP.timep);
        nextP.id=i;
        nextP.pidid=pthread_self();
        stack[in]=nextP;
        in=(in+1)%BUFFERSIZE;
        count++;
        ++i;
        sem_post(&sem);
    }
}

void customer(void)
{
    int m=0;
    while(m&lt;10)
    {
        sleep(ran_time());
        while(in==out);
        sem_wait(&sem);
        nextC.timep=stack[out].timep;
        nextC.id=stack[out].id;
        nextC.pidid=stack[out].pidid;
        out=(out+1)%BUFFERSIZE;
        count--;
        ++m;
        printf("customer:customer_pid: %d ;time:%s ; id: %d ; pidid: %d  count:%d\n",pthread_self(),ctime(&nextC.timep),nextC.id,nextC.pidid,count);
        sem_post(&sem);
    }
}

int main(void)
{
    pthread_t t1,t2,t3,t4;
    pthread_attr_t attr;
    sem_init(&sem,0,1);
    pthread_attr_init(&attr);
    pthread_create(&t1,&attr,(void*)producer,NULL);
    pthread_create(&t2,&attr,(void*)customer,NULL);
    pthread_create(&t3,&attr,(void*)producer,NULL);
    pthread_create(&t4,&attr,(void*)customer,NULL);
    pthread_join(t1,NULL);
    pthread_join(t2,NULL);
    pthread_join(t3,NULL);
    pthread_join(t4,NULL);
}