fork和pipe，一个父进程和多个子进程的通信问题

[LixueDaddy]

各位大牛好啊，最近在学习进程控制，现在用到了fork和pipe，一个父进程和多个子进程的通信问题。
是多个子进程将数据发送到父进程，父进程判断后决定关闭某个子进程。现在遇到的问题是，我的父进程读取的信息都是第一个子进程的内容，其他的子进程的内容被忽略了。
怎样解决这个问题?
还有，当父进程想给某几个特定的子进程发送消息，是怎样具体实现的，谢谢啦。

# include <unistd.h>
# include <time.h>
# include <stdlib.h>
# include <stdio.h> 
# include <string.h>



int main(int argc, char *argv[])
{
	int iSecret, count;
	int pCount= atoi(argv[1]);
	pid_t* pid[pCount];
	int mtspipe[2], stmpipe[2];
	char buf[200], len;
	

	// Create the pipe: master to slave, slave to master. 
	//If succeed return 0, else -1;	
	if(pipe(mtspipe))
	{
		fprintf(stderr,"Create master to slave pipe failed.\n");
		return EXIT_FAILURE;
	}
	
	if(pipe(stmpipe))
	{
		fprintf(stderr,"Create slave to master pipe failed.\n");
		return EXIT_FAILURE;
	}

	//Create the child process
	if(argc>1)
	{
		for(count=0;count<pCount;count++)
		{
			
		pid[count] = fork();
		if(pid[count]==0)   //child process
		{
			close(mtspipe[1]);  //close write of mtspipe
			close(stmpipe[0]);  //close read of stmpipe
			//char str[65];

					srand(time(NULL));
					iSecret = rand()%6+1;
					sprintf(buf,"%d:%d",getpid(),iSecret);
					write(stmpipe[1],buf,strlen(buf));
					
					printf("This is what we send to master:%s\n",buf);
		
			return EXIT_SUCCESS;
		}
		
		else if(pid[count] == -1)
			{
				printf("Error\n");
			}
		else    // master process
		{
		
			close(mtspipe[0]);  //close read of mtspipe
			close(stmpipe[1]);  //close write of stmpipe
			len=read(stmpipe[0],buf,sizeof(buf)); //read from stmpipe
			printf("This is what we read from slave:%s\n",buf);
			sleep(1);
		}
		}

		//wait for all the sub-process to terminate
		int i = 0;
		for (; i < pCount; ++i) {
		    int status;
		    while (-1 == waitpid(pid[i], &status, 0));
		if (WIFEXITED(status))
			printf("Child exited with code %d\n", WEXITSTATUS(status));
		else if (WIFSIGNALED(status))
			printf("Child terminated abnormally, signal %d\n", WTERMSIG(status));
		}

		
	}
	else
	{
	printf("The command has no other arguments\n");
	}
	return 0;
}

[qq120848369]

close(mtspipe[0]); //close read of mtspipe
close(stmpipe[1]); //close write of stmpipe

这两个你父进程关了多少次了，而且stmpipe[1]不应该在循环内关闭，否则你让后面的都子进程怎么继承它。

[qq120848369]

for (; i < pCount; ++i) {
int status;
while (-1 == waitpid(pid[i], &status, 0));
if (WIFEXITED(status))
printf("Child exited with code %d\n", WEXITSTATUS(status));
else if (WIFSIGNALED(status))
printf("Child terminated abnormally, signal %d\n", WTERMSIG(status));
}

再就是这里，你应该判断-1的情况下errno是什么,EINTR不应该让++i发生。

[LixueDaddy]

我为每个子程序都创建了管道来与父进程交换信息，这样会不会造成资源浪费，两对管道是否可以完成这个任务？前者可以解决之前遇到的只读取第一个子程序的问题。[Quote=引用 1 楼 的回复:]

close(mtspipe[0]); //close read of mtspipe
close(stmpipe[1]); //close write of stmpipe

这两个你父进程关了多少次了，而且stmpipe[1]不应该在循环内关闭，否则你让后面的都子进程怎么继承它。
[/Quote]

[LixueDaddy]

的确，我还需要分析一下EINTR造成的影响。谢谢啦。[Quote=引用 2 楼 的回复:]

for (; i < pCount; ++i) {
int status;
while (-1 == waitpid(pid[i], &status, 0));
if (WIFEXITED(status))
printf("Child exited with code %d\n", W……
[/Quote]

[qq120848369]

[Quote=引用 3 楼 的回复:]

我为每个子程序都创建了管道来与父进程交换信息，这样会不会造成资源浪费，两对管道是否可以完成这个任务？前者可以解决之前遇到的只读取第一个子程序的问题。引用 1 楼 的回复:

close(mtspipe[0]); //close read of mtspipe
close(stmpipe[1]); //close write of stmpipe

这两个你父进程关了多少次了，而且……
[/Quote]

写入量小于PIPE_SIZE可以原子写入，否则你就得掂量掂量了，注意字节流拆包问题。

另外，能不能别把计算机想的和傻逼一样，有几个人能遇到所谓的性能瓶颈。

[weiguozhe]

# include <unistd.h>
# include <time.h>
# include <stdlib.h>
# include <stdio.h> 
# include <string.h>



int main(int argc, char *argv[])
{
    int iSecret, count;
    int pCount= atoi(argv[1]);
    //pid_t *pid[pCount];
	pid_t pid[pCount];
    int mtspipe[2], stmpipe[2];
    char buf[200], len;
    
	
    // Create the pipe: master to slave, slave to master. 
    //If succeed return 0, else -1;    
    /*if(pipe(mtspipe))
    {
        fprintf(stderr,"Create master to slave pipe failed.\n");
        return EXIT_FAILURE;
    }*/
    
    if(pipe(stmpipe))
    {
        fprintf(stderr,"Create slave to master pipe failed.\n");
        return EXIT_FAILURE;
    }
	
    //Create the child process
    if(argc>1)
    {
        for(count=0;count<pCount;count++)
        {
            
			pid[count] = fork();
			if(pid[count]==0)   //child process
			{
				//close(mtspipe[1]);  //close write of mtspipe
				//close(stmpipe[0]);  //close read of stmpipe
				//char str[65];
				
				srand(time(NULL));
				iSecret = rand()%6+1;
				sprintf(buf,"%d:%d",getpid(),iSecret);
				write(stmpipe[1],buf,strlen(buf));
				
				printf("This is what we send to master:%s\n",buf);
				
				return EXIT_SUCCESS;
			}
			
			else if(pid[count] == -1)
            {
                printf("Error\n");
            }
			else    // master process
			{
				
				//close(mtspipe[0]);  //close read of mtspipe
				//close(stmpipe[1]);  //close write of stmpipe
				len=read(stmpipe[0],buf,sizeof(buf)); //read from stmpipe
				printf("This is what we read from slave:%s\n",buf);
				sleep(1);
			}
        }
		
        //wait for all the sub-process to terminate
        int i = 0;
        for (; i < pCount; ++i) 
		{
            int status;
            //while (-1 == waitpid(pid[i], &status, 0));
			waitpid(pid[i], &status, 0);
			if (WIFEXITED(status))
				printf("Child exited with code %d\n", WEXITSTATUS(status));
			else if (WIFSIGNALED(status))
				printf("Child terminated abnormally, signal %d\n", WTERMSIG(status));
        }
		
        
    }
    else
    {
		printf("The command has no other arguments\n");
    }
    return 0;
}