#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>

/* Important: run this program as root, otherwise, 
 * you won't be able to do setgid */
int main()
{
	int gid, num_procs;
	unsigned int i;
	pid_t pid;

	/* We plan to create 2 processes with group id equal to 1024 */
	gid = 1024;
	num_procs = 2;
	setgid(gid);

	while (num_procs--)
	{
		pid = fork();
		if (!pid)
		{
			/* Verify that child has the same gid as parent */
			printf("pid = %d, gid = %d\n", getpid(), getgid());

			/* Add your own CPU-intensive calculations here */
			i = 0xFFFFFFFF;
			while (i)
				i--;

			// add some code to read /proc/getpid()/stat

			return 0;
		}
	}

	return 0;
}