IO进程线程作业

原创已于 2022-10-14 20:54:06 修改 · 113 阅读

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#c++ #c语言 #算法

于 2022-10-14 19:09:06 首次发布

本文介绍了一个使用pthread库实现线程间同步的经典案例，通过三个线程按顺序打印字符A、B、C，展示了如何利用互斥锁和条件变量来协调线程间的执行顺序。此外，还提供了一个父子进程通过无名管道进行通信的例子。

ABCABCABC

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

char a='A';
char b='B';
char c='C';
int flag=0;

//互斥锁
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
//条件变量
pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER; 
pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER; 
pthread_cond_t cond3 = PTHREAD_COND_INITIALIZER; 

void* callBack1(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		if(1==flag||flag==2)//条件为0不休眠
		{
			pthread_cond_wait(&cond1,&mutex);
		}
		printf("%c",a);
		flag=1;
		
		pthread_cond_signal(&cond2);
		pthread_mutex_unlock(&mutex);

	}
	pthread_exit(NULL);
}

void* callBack2(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		if(flag==0||flag==2)//条件为1不休眠
		{
			pthread_cond_wait(&cond2,&mutex);
		}
		printf("%c",b);
		flag=2;

		pthread_cond_signal(&cond3);
		pthread_mutex_unlock(&mutex);
	}
	pthread_exit(NULL);
}

void* callBack3(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		if(0==flag||flag==1)//条件为2不休眠
		{
			pthread_cond_wait(&cond3,&mutex);
		}
		printf("%c\n",c);
		flag=0;

		pthread_cond_signal(&cond1);
		pthread_mutex_unlock(&mutex);
	}
	pthread_exit(NULL);
}

int main(int argc, const char *argv[])
{
	pthread_t tid1,tid2,tid3;
	//A
	if(pthread_create(&tid1,NULL,callBack1,NULL)!=0)
	{
		perror("pthread_create");
		return -1;
	}
	//B
	if(pthread_create(&tid2,NULL,callBack2,NULL)!=0)
	{
		perror("pthread_create");
		return -1;
	}
	//C
	if(pthread_create(&tid3,NULL,callBack3,NULL)!=0)
	{
		perror("pthread_create");
		return -1;
	}

	pthread_join(tid1,NULL);
	pthread_join(tid2,NULL);
	pthread_join(tid3,NULL);

	pthread_mutex_destroy(&mutex);
	pthread_cond_destroy(&cond1);
	pthread_cond_destroy(&cond2);
	pthread_cond_destroy(&cond3);

	return 0;
}

父子进程对话

#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>

int main(int argc, const char *argv[])
{
	int pfd[2];//无名管道
	if(pipe(pfd)<0)//判断条件，-1为创建无名管道失败
	{
		perror("pipe");
		return -1;
	}
	printf("无名管道创建成功\n");
	int pfd2[2];//无名管道
	if(pipe(pfd2)<0)//判断条件，-1为创建无名管道失败
	{
		perror("pipe");
		return -1;
	}
	printf("无名管道2创建成功\n");

	char buf1[128];
	int res1=0;

	pid_t pid = fork();//创建子进程
	if(pid > 0)
	{
		//父进程代码区
		while(1)
		{

			bzero(buf1,sizeof(buf1));
			printf("父进程对子进程说:");
			fgets(buf1,sizeof(buf1),stdin);//父进程发送给子进程信息
			buf1[strlen(buf1)-1] = '\0';

			res1=write(pfd[1],buf1,sizeof(buf1));
			//向管道文件写入字符串buf1
			if(strcmp(buf1,"quit")==0)
			{
				break;
			}
			if(res1<0)
			{
				perror("write");
				return -1;
			}

		/********************************************/


			bzero(buf1,sizeof(buf1));
			res1=read(pfd2[0],buf1,sizeof(buf1));
			//从管道文件中读取字符串buf1
			if(strcmp(buf1,"quit")==0)
			{
				break;
			}
			if(res1<0)
			{
				perror("read");
				return -1;
			}
			printf("父进程：子进程说:%s\n",buf1);

		}

	}
	else if(0==pid)
	{
		//子进程代码区
		while(1)
		{
			bzero(buf1,sizeof(buf1));
			res1=read(pfd[0],buf1,sizeof(buf1));
			//从管道文件中读取字符串buf1
			if(strcmp(buf1,"quit")==0)
			{
				break;
			}
			if(res1<0)
			{
				perror("read");
				return -1;
			}
			printf("子进程：父进程说:%s\n",buf1);

		/********************************************/

			bzero(buf1,sizeof(buf1));
			printf("子进程对父进程说:");
			fgets(buf1,sizeof(buf1),stdin);//父进程发送给子进程信息
			buf1[strlen(buf1)-1] = '\0';

			res1=write(pfd2[1],buf1,sizeof(buf1));
			//向管道文件写入字符串buf1
			if(strcmp(buf1,"quit")==0)
			{
				break;
			}
			if(res1<0)
			{
				perror("write");
				return -1;
			}
		}

	}
	else
	{
		//创建子进程失败
		perror("fokr error");
		return -1;
	}


	return 0;
}