Linux中四个fork()后创建了多少个进程? [英] How many processes are created after four fork() in Linux?

问题描述

我在操作系统教科书中看到了一个愚蠢的问题.问题如下:
假设所有fork系统调用都成功.执行如下所示程序后.屏幕上有多少行?
我假设每个 fork 调用都会使进程加倍，因此结果应该是创建了 16 个进程.但是当我从教科书中输入相同的代码时，我得到了 30 行.这是结果和代码:
http://imgur.com/zrdOP0X

I have a dumb question seeing on the Operating system textbook. The question is below:
Assume that all fork system calls are successful.After executing program shown below. How many lines are on the screen?
I assume that every fork call doubles the processes, so the result should be 16 process are created. But when I type the same code from the textbook, I got 30 lines. Here is the result and the code:
http://imgur.com/zrdOP0X

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

int main(){
    fork();
    printf("After fork1
");
    fork();
    printf("After fork2
");
    fork();
    printf("After fork3
");
    fork();
    printf("After fork4
");
}

推荐答案

结果应该是这样的:

fork1叉子2叉子3叉子4叉子4叉子3叉子4fork4
叉子2叉子3叉子4叉子4叉子3叉子4叉子4叉子1叉子2叉子3叉子4叉子4叉子3叉子4fork4
叉子2叉子3叉子4叉子4叉子3叉子4fork4

(空格只是为了更好的阅读)

(the spaces are only for better reading)

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