Amount of processes in fork() statements including program

Question

I am learning about forks and processes in linux and have a question concerning the initial parent process. Is this initial parent process considered the program?

For example this code where I create 2 forks

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

int main(int argc, char **argv, char **envp)
{
    printf("%d *\n", getpid());
    fork();
    printf("%d *\n", getpid());
    fork();
    printf("%d *\n", getpid());
    sleep(20);
    return EXIT_SUCCESS;
}

From what I know there would be an initial parent process(which I believe is the program), and then there would be the initial fork creating a child process.

This leaves 2 processes. Then the other fork creates 2 more child processes for 5 processes total including the initial parent process.

From that understanding, the total number of child processes would be 3(2^2-1) and the total processes created besides the initial parent process would be 4.

Is my thinking correct?

Also, what would cause a fork to fail?

Answer 1

Not exactly, each fork() call creates exactly one additional process. In this example You'd have a total of 4 processes, including parent process.

EDIT: I recommend reading manual for methods that You learn and use e.g. http://man7.org/linux/man-pages/man2/fork.2.html

You'll find there all the explanation, including possible failure reasons.