在fork（）中检测子进程创建

Question

The fork() system call makes two identical copies of the address space, one for parent, the other for the child.

When using fork with an if statement, how many times will the child process be created in the following code?

fork();
pid=fork();
if(pid==0)
{
fork();
}

Answer 1

Add a little extra code to get something like:

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

int main()
{
    pid_t pid;
    pid = fork();
    if (pid != 0) printf("%d\n", pid);
    pid = fork();
    if (pid != 0) printf("%d\n", pid);
    if(pid==0)
    {
        pid = fork();
        if (pid != 0) printf("%d\n", pid);
    }
    return 0;
}

Then compile, execute, and check its output: 5 child process IDs .