linux process question

[blob84]

Hi, I don't know why when i run this code with redirection of output,

a.out > file

, it seems that the process child is not adopted by init.

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

static void ex1(void)
{
printf("student\n");
}
static void ex2(void)
{
printf("prof \n");
}

int main(void)
{
	pid_t pid1,pid2;
	int s=0, c;

	pid1=fork();
	if (pid1==0) { 
		atexit(ex1); 
		atexit(ex2);
		while ((c=getppid()) != 1) { 
			printf("pid=%d\n", c);		
			s=s+1;
			printf("userc: %d\n",s);
			exit(0);
		}
	}		
	else {
		atexit(ex1); 
		atexit(ex2);
		printf("userf: %d\n",s);
		exit(0);
	}
}

[grumpy]

Because your program is run in a process that is a child of the shell in which you type "a.out > file". That shell process will continue to exist until the child exits. Which means the child never becomes an orphan, and is never adopted by init.

[blob84]

what are you saying is that the parent process doesn't exit?

[grumpy]

The parent process waits for the child to terminate before it continues execution (and continuing execution is a precursor to exiting).