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

int main()
{
 printf("Real user ID: %d\n", getuid());
 printf("Effective user ID: %d\n", geteuid());
 printf("Real group ID: %d\n", getgid());
 printf("Effective group ID: %d\n", getegid());
 return 0;
}