IORDUP
X_OK | ((iop->flag & IORDUP) ? R_OK : W_OK),
if (iop->flag & IORDUP) /* possible exec <&p */
iop->flag = IODUP | (c == '<' ? IORDUP : 0);
(type == IODUP && (iop->unit == !(flag & IORDUP))) ? iop->unit :
if (flag & IORDUP)