孩子和家长的PID叉（）; [英] Child and Parent pid with fork();

问题描述

我试图做一个程序，让9子进程，所以我用叉子只有9倍，如果我们的父亲，像这样的：

I'm trying to make a program which make 9 child process, so I use fork 9 times only if we are the father, like this:

for (int i = 0; i < 9; i++) {   // Creo 9 hijos.
    if (child_pid > 0) {
        child_pid = fork();
        childs[i] = child_pid;
    }
    if (child_pid < 0)
        printf("Error...\n");
}

现在，我必须打印在每个孩子他是什么样的孩子，从0开始，所以我想这个问题：

Now, I have to print on each children what children he is, starting from 0, so I was thinking about this:

printf("This is child #%d\n", getpid() - getppid());

但是我不知道，这是否总是工作？如果当父创建儿童操作系统创建另一个进程？儿童的人数将停止？
最后，如​​果答案是肯定的，我怎么能作出这样的#N孩子们知道，他是孩子数n？

推荐答案

您可以使用 I 变量来告诉你是哪个孩子，但你的循环逻辑不正确。它应该是这样的：

You can use the i variable to tell which child you are in, but the logic of your loop is incorrect. It should go like this:

for (int i = 0; i < 9; ++i) {
    child_pid = fork();

    if (child_pid == 0) {
        // We are the child. The value of the i variable will tell us which one.
        // If i == 0 we are the first child, i == 1 and we are the second, and so on.
        printf("We are child #%d\n", i);
        exit(EXIT_SUCCESS);
    }

    if (child_pid < 0) {
        // Forking failed.
        perror("fork()");
        exit(EXIT_FAILURE);
    }

    // Otherwise we are the parent and forking was successful; continue the loop.
}

不要求操作系统按顺序分配进程ID。如果另一进程正在使用的下一个，这将在顺序分配方法被跳过，但操作系统可能真正分配一个随机数作为只要pid的，因为它是在不使用

The operating system is not required to assign process IDs in sequential order. If another process is using the next one, it would be skipped over in a sequential assignment method, but the OS could really assign a random number as the pid as long as it is not in use.

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