多线程按序输出字符

来源：互联网发布：知乎app电脑版编辑：程序博客网时间：2024/04/29 19:36

题目：

有三个线程分别打印字符A、B和C，要求按照ABC这样的顺序一直打印字符，形成ABCABCABC........

需要使用信号量进行处理，源代码如下

#include <stdio.h>#include <pthread.h>#include <semaphore.h>#include <string.h>#include <stdlib.h>void* pt1(void* arg);void* pt2(void* arg);void* pt3(void* arg);sem_t s[3]; int main() {sem_init(&s[0], 0, 1);sem_init(&s[1], 0, 0);sem_init(&s[2], 0, 0);pthread_t pid[3];pthread_create(&pid[0], NULL, pt1, NULL);pthread_create(&pid[1], NULL, pt2, NULL);pthread_create(&pid[2], NULL, pt3, NULL);int i;for(i=0; i<3; i++)pthread_join(pid[i], NULL);return 0;} void* pt1(void* arg) {while(1) {sleep(1);sem_wait(&s[0]);printf("A");fflush(stdout);sem_post(&s[1]);}}void* pt2(void* arg) {while(1) {sleep(1);sem_wait(&s[1]);printf("B");fflush(stdout);sem_post(&s[2]);}}void* pt3(void* arg) {while(1) {sleep(1);sem_wait(&s[2]);printf("C");fflush(stdout);sem_post(&s[0]);}}

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