if (!number)
if (number == 0)
group_keys (int number, char *key[]){  int result = 0;  int i;  struct group *grp;  if (!number)    {      setgrent ();      while ((grp = getgrent()) != NULL)	print_group (grp);      endgrent ();      return result;    }  for (i = 0; i < number; ++i)    {      if (isdigit (key[i][0]))	grp = getgrgid (atol (key[i]));      else	grp = getgrnam (key[i]);      if (grp == NULL)	result = 2;      else	print_group (grp);    }  return result;}