getpgid

static VALUE
proc_getpgid(VALUE obj, VALUE pid)
{
#if defined(HAVE_GETPGID) && !defined(__CHECKER__)
    rb_pid_t i;

    rb_secure(2);
    i = getpgid(NUM2PIDT(pid));
    if (i < 0) rb_sys_fail(0);
    return PIDT2NUM(i);
#else
    rb_notimplement();
#endif
}