Linux主线程接收数据，子线程分别对其操作后输出

来源：互联网发布：恒韵琴行淘宝编辑：程序博客网时间：2024/06/12 23:44

本例子虽小，但是融合的线程同步，线程回收和信号量的知识。

需要注意pthread_join()和pthread_exit()的用法和区别：

pthread_join一般是主线程来调用，用来等待子线程退出，因为是等待，所以是阻塞的，一般主线程会依次join所有它创建的子线程。
pthread_exit一般是子线程调用，用来结束当前线程。
子线程可以通过pthread_exit传递一个返回值，而主线程通过pthread_join获得该返回值，从而判断该子线程的退出是正常还是异常。

#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <pthread.h>#include <semaphore.h>sem_t bin_sem;int data;void *thread_functionB(void *arg);void *thread_functionA(void *arg);int main(void){int res;pthread_t a_thread;pthread_t b_thread;void *thread_resultA;void *thread_resultB;if(sem_init(&bin_sem, 0, 0)){printf("sem init error!\n");exit(EXIT_FAILURE);}res = pthread_create(&a_thread, NULL, thread_functionA, NULL);if(res != 0){perror("Thread creation failed");exit(EXIT_FAILURE);}res = pthread_create(&b_thread, NULL, thread_functionB, NULL);if(res != 0){perror("thread creation failed!");exit(EXIT_FAILURE);}//sem_wait(&bin_sem);printf("input a number:\n");scanf("%d",&data);sem_post(&bin_sem);if(pthread_join(a_thread, &thread_resultA)!=0){perror("thread a join error!");exit(EXIT_FAILURE);}if(pthread_join(b_thread, &thread_resultB)!=0){perror("thread b join error!");exit(EXIT_FAILURE);}printf("thread A has joined, it returned:%s\n", (char *)thread_resultA);printf("thread B has joined, it returned:%s\n", (char *)thread_resultB);printf("final data is:%d\n", data);exit(EXIT_SUCCESS);}void *thread_functionA(void *arg){sem_wait(&bin_sem);data++;printf("thread A ++\n");sem_post(&bin_sem);pthread_exit("thread A has exited");}void *thread_functionB(void *arg){sem_wait(&bin_sem);data++;printf("thread B ++\n");sem_post(&bin_sem);pthread_exit("thread B has exited");}

编译并运行结果正确：

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