管（）不能很好地工作 - Linux的 [英] Pipe() doesn't work well - linux

问题描述

我试图让使用管道通信的程序。这就是我想要做的事：用户发送正整数。如果用户发送一个负数通信结束。父进程打印的最大数量和最小数。这是我尝试：

I'm trying to make a program using the pipe communication. This is what I'm trying to do: the user sends positive integers. If the user sends a negative number the communication ends. The parent process prints the maximum number and the minimum number. This is what I tried:

#include <unistd.h>
#include <stdio.h>

main(){
int pfd[2];
int buff[200];
pipe(pfd);
if(fork()==0){
   close(pfd[0]);
   int n;
   printf("Give a number: ");
   scanf("%d",&n);
   while(n >=0 ){
      write(pfd[1],&n,1);
      printf("Give a number: ");
      scanf("%d",&n);
   }
  exit(0);
  }
else{
  close(pfd[1]);
  read(pfd[0],buff,sizeof(buff));
  printf("The parent read %d:",*buff);
  wait(0);
}
}

本的printf（父读取％D：，* BUFF）; 只打印给我的第一个号码。谁能更好的是我必须做的解释一下吗？如何打印所有的缓存？我写仅1中的缓冲区号，这就是它？如何找到在最大和最小多少？我很困惑！ （

This printf("The parent read %d:",*buff); prints only the first number I gave. Can someone explain to me better what I have to do? How to print all the buffer? Am I writing only 1 number in the buffer and that's it? How do I find the maximum and the minimum number? I am very confused! :(

推荐答案

这是一个方式做什么，我想你想用很少的修改做。
请注意， BUFF 不再是一个数组，我们使用的管材本身作为临时存储为我们打印的数字。

This is a way to do what I think you're trying to do with a very few modifications. Notice that buff is no longer an array and that we use the pipe itself as temporary storage as we print the numbers.

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

int main(void)
{
    int pfd[2];
    int buff;
    int max,min;

    pipe(pfd);
    if(fork()==0){
        close(pfd[0]);
        int n;
        printf("Give a number: ");
        scanf("%d",&n);
        while(n >=0 ){
            write(pfd[1],&n,sizeof(n));
            printf("Give a number: ");
            scanf("%d",&n);
        }
        exit(0);
    }
    else {
        close(pfd[1]);
        printf("The parent read ");

        if (read(pfd[0],&buff,sizeof(int))) {
            max = buff;
            min = buff;
            printf("%d",buff);
        }


        while (read(pfd[0],&buff,sizeof(int))) {
            if (buff > max)
            max = buff;
            else if (buff < min)
            min = buff;
            printf("%d:",buff);
        }

        printf("\n");

        printf("The maximum value is: %d.\n The minimum value is: %d.\n",max,min);
        wait(NULL);
    }
}

这篇关于管（）不能很好地工作 - Linux的的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！