Question

...
int main(void)
{
    int i;
    for(i=0;i<2;i++){
      switch(fork()){
        case 0:
          sleep(1);
          break;
        default:
          sleep(1);
       }
    }
    while(i--) wait(NULL);
    return 0;
}

Hi. I’m trying to understand processes and forks.

I’m not sure how many processes does this code snippet create.

1 for the main program, then the main program duplicates itself (a child process is created), and then the child duplicates itself (2 children and the main process).

So those are 3 processes.

Am I correct or am I missing something?

Answer 1

There is a for loop in the main thread (t1) that will call fork() twice (-> t1.1, t1.2). The first forked-thread (t1.1) has one more iteration, so it creates another (-> t1.1.1). Neither t1.2 nor t1.1.1 has any more iterations left, so no more threads forked.

This leaves us with 4 threads altoghether