如何使用fork（）系统调用创建一级进程树？

Question

I want to create a one level process tree using fork() system call, which looks as follows for n = 4 process

I have tried this with the following code but this is not working. (here 1 is a child of parent process )

    for(i = 0 ;i < n; i++){
    chid = fork();
    if ( chid == 0 ){
        printf("%d\n",getpid());
        while(++i < n){
            chid = fork();
            if(chid == 0){
                printf(" %d ",getpid());
                break;
            }
        }
    }
    else
        break;
} 

How can I make this ?

Answer 1

#include<stdio.h>

int main()
{
  int i;
  pid_t  pid;

  for(i=0; i<5; i++)
  {
    pid = fork();
    if(pid == 0)
      break;
  }
  printf("pid %d ppid %d\n", getpid(), getppid());
  if(pid == 0)
  {
    /* child process */
  }
}

Based on the discussion, here is the modified program.

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

int main()
{
  int i;
  pid_t  pidparent, pid;

  if( (pidparent = fork()) == 0 )
  {
    for(i=0; i<3; i++)
    {
      pid = fork();
      if(pid == 0)
        break;
    }
    if(pid == 0)
    {
      printf("child %d parent %d\n", getpid(), getppid());
    }
  }
  else
  {
    printf("parent %d \n", pidparent);
  }
  /* printf("pid %d ppid %d\n", getpid(), getppid()); */
}