question about fork

i'm experimenting fork function and i found this code

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <wait.h>
#include <fcntl.h>
#include <unistd.h>

int main(void)
{
	int fd[2];
	pid_t p;

	p = fork();
	fork();
	if (p>0) { fork();}
	fork();
	fork();
	sleep(30);
	exit(0);
}

I thought that there were 2^5 processes after running this code , but there were less processes.
Why?

Because when fork() returns, 2 processes exist: one parent, and one child.

1. So after the first fork(), you have 2 processes.
2. This 2 processes calls fork() again; you have now 4 processes.
3. The third fork() is only performed by the children, resulting 4 more processes (now 6=4+2 in total).
4. These 6 processes calls fork() twice, resulting 2*2*6 = 24 processes in total.

From this, it should be clear that several fork() one after the other causes an exponential growth of the number of processes.

Cheers,
/Lew

The relationship between fork and the number of processes created isnt 2^n but 2n...and in this program it will be 2n-2 due to...if (p>0) { fork();}

May I suggest to check this assumption against reality by writing a small program?

Thanks,
/Lew

Non zero return value goes to parent not child...and after double cheking my calculations yes it will be 24 procs.

Thanks shamrock for double checking.

Cheers,
/Lew

thanks NH2 for explanation!