最近在学习OSTEP这本书，留个课后习题笔记。

Homework(code):

chapter cpu-api

8. Write a program that creates two children, and connects the standard output of one to the standard input of the other, using the pipe() system call.

Code:

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

int main()
{
    int pi[2];
    int p = pipe(pi); // create pipe
    if (p < 0)
    {
        fprintf(stderr, "pipe failed");
        exit(1);
    }
    int rc[2];
    for (int i = 0; i < 2; ++i)
    {
        rc[i] = fork(); // create child process
        char *buf;
        if (rc[i] < 0)
        {
            fprintf(stderr, "fork failed");
            exit(1);
        }
        else if (rc[i] == 0)
        {
            switch (i)
            {
            case 0:
                // child process 0
                buf = "inputs...";
                write(pi[1], buf, strlen(buf));
                return 0;
            case 1:
                // child process 1
                buf = malloc(20);
                memset(buf, 0, 20);
                read(pi[0], buf, 20);
                printf("child1 read from child0 through pipe:\n(%s)\n", buf);
                return 0;
            }
            break;
        }
    }
    waitpid(rc[0], NULL, 0);
    waitpid(rc[1], NULL, 0);
    return 0;
}

参考了一下网络上的题解，原代码感觉不是很优雅，用了不建议使用的函数，于是理解原理后，改写了一个比较优雅的版本。