如何实现多进程的管道？ [英] How to implement pipes for multiple processes?

问题描述

我创建多个进程和的我需要为每个进程创建两个命名管道。的

有关每一个孩子，一个管道将用于从母公司int值;一个用于发送到int数组父。家长会做一些事情的，而从孩子的获得新的数据。

For each child, one pipe will be used to get int value from parent; one for sending to int arrays to parent. Parent will do some things while getting new data from childs.

该基地code：

#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h> // for reaching unix operations


int main(int argc, char *argv[]){
    pid_t main = getpid();

    int N = 30;
    int i;
    pid_t* children = (pid_t*) malloc(sizeof(pid_t) * N);
    for(i = 0; i < N; i++){
        pid_t child = fork();
        if ( child == 0){
            pid_t me = getpid();
            printf("I'm a child and my pid is: %d\n", me);
             sleep(1);
            // exit(4);
            return me * 2;
        } else if ( child < 0){
            // printf("Could not create child\n");
        } else {
            children[i] = child;
            // printf("I have created a child and its pid %d\n", child);
        }
    }

    // The child never reaches here
    for(i = 0; i < N; i++){
        int status;
        waitpid(children[i], &status, 0);
        printf("Process %d exited with return code %d\n", children[i], WEXITSTATUS(status));
    }
    return 0;
}

我试过很多事情没有成功，我迷路了。你能帮助我继续吗？

I tried many things with no success and I'm lost. Can you help me to continue?

任何帮助AP preciated！谢谢你。

Any help is appreciated! Thank you.

推荐答案

下面是如何建立一个管道每个子流程，使每个孩子写父：

Here's how to set up one pipe for each child process so that each child writes to the parent:

因为你需要为每一个孩子两个文件描述符，声明：

Since you need two file descriptors for each child, declare:

int fd[2 * N];

适当地初始化它们：

Initialize them appropriately:

for (int i = 0; i < N; i++) {
    pipe(&fd[2*i]);
}

---

在 I -th子进程，使用方法：

---

Inside the i-th child process, use:

write(fd[2*i + 1], write_buffer, SIZE) 

写信给家长，并在家长使用：

to write to the parent, and in the parent use:

 read(fd[2*i], read_buffer, SIZE) 

从读我 -th孩子​​。

要关闭该管道：

在 I -th孩子​​，你可以使用

Inside the i-th child, you can use

close(fd[2*i]) 

向右走，看到，因为你只是写。你写完电话后

right away, seeing as you're only writing. After you're done writing call

close(fd[2*i + 1]) 

以关闭管道的写端

to close the write end of the pipe.

的情况是在父并行：从读书时，我 -th孩子​​可以

The situation is parallel in the parent: when reading from the i-th child you can

close(fd[2*i + 1]) 

向右走，因为你不写，你就大功告成了读调用后

right away, since you're not writing, and after you're done reading call

close(fd[2*i])

，关闭管的读端

由于需要的两个的每个子进程的管道，建立两个数组 - 为孩子们写于母公司包含一个管道，并包含一个管道父写给孩子

Since you need two pipes per child process, create two arrays - one containing pipes for the children writing to the parent, and one containing pipes for the parent writing to the children.

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