名稱(chēng)：

sem_init

功能：

initialize an unnamed semaphore,初始化信號(hào)量sem_t，初始化的時(shí)候可以指定信號(hào)量的初始值，以及是否可以在多進(jìn)程間共享。

頭文件：

#include <semaphore.h>

函數(shù)原形：

int sem_init(sem_t *sem, int pshared, unsigned int value);

參數(shù)：

?

返回值：

sem_init() returns 0 on success; on error, -1 is returned, and errno is set to indicate the error.

名稱(chēng)：

sem_wait

sem_trywait

功能：

lock a semaphore?一直阻塞等待直到信號(hào)量 > 0.

頭文件：

#include <semaphore.h>

函數(shù)原形：

int sem_wait(sem_t *sem);

int sem_trywait(sem_t *sem);

參數(shù)：

?

返回值：

All of these functions return 0 on success; on error, the value of?the semaphore is left unchanged, -1 is returned, and errno is set to indicate the error.

名稱(chēng)：

sem_timedwait

功能：

lock a semaphore，阻塞等待若干時(shí)間直到信號(hào)量 > 0

頭文件：

#include <semaphore.h>

函數(shù)原形：

int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout);

參數(shù)：

?

返回值：

All of these functions return 0 on success; on error, the value of?the semaphore is left unchanged, -1 is returned, and errno is set to indicate the error.

名稱(chēng)：

sem_post

功能：

unlock a semaphore，使信號(hào)量加1。

頭文件：

#include <semaphore.h>

函數(shù)原形：

int sem_post(sem_t *sem);

參數(shù)：

?

返回值：

sem_post() returns 0 on success; on error, the value of the semaphore is left unchanged, -1 is returned, and errno is set to indicate the error.

名稱(chēng)：

sem_destroy

功能：

destroy an unnamed semaphore釋放信號(hào)量。和sem_init對(duì)應(yīng)

頭文件：

#include <semaphore.h>

函數(shù)原形：

int sem_destroy(sem_t *sem);

參數(shù)：

?

返回值：

sem_destroy() return 0 on success;on error,-1 is returned,an errno is set to indicate the error.

#include <stdlib.h>

#include <pthread.h>

#include <stdio.h>

#include <unistd.h>

#include <semaphore.h>

?

#define NUM 5

?

int queue[NUM];

sem_t blank_number,product_number;

?

void *producer(void *arg)

{

???int p = 0;

???while(1) {

???????//blank_num = 5生產(chǎn)者最多生產(chǎn)5個(gè)

???????//一直阻塞等待信號(hào)量大于0

???????sem_wait(&blank_number);

???????queue[p] = rand() % 1000 + 1;

???????printf("Produce %d\n",queue[p]);

???????//product_number = 0 ->1

???????//使信號(hào)量加1

???????sem_post(&product_number);

???????p = (p + 1) % NUM;

???????sleep(rand() % 5);

???}

}

?

void *consumer(void *arg) {

???int c = 0;

???while (1) {

???????//等待信號(hào)量大于0

???????sem_wait(&product_number);

???????printf("Consume %d\n",queue[c]);

???????queue[c] = 0;

???????//使信號(hào)量加1

???????sem_post(&blank_number);

???????c = (c + 1) % NUM;

???????sleep(rand() % 5);

???}

}

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

{

???pthread_t pid,cid;

???//將blank_num信號(hào)量初始化的值為5

???sem_init(&blank_number,0,NUM);

???//將product_number信號(hào)量初始化的值變?yōu)?

???sem_init(&product_number,0,0);

???pthread_create(&pid,NULL,producer,NULL);

???pthread_create(&cid,NULL,consumer,NULL);

???pthread_join(pid,NULL);

???pthread_join(cid,NULL);

???sem_destroy(&blank_number);

???sem_destroy(&product_number);

???return 0;

}