what does read(2) do if O_NDELAYed?

[Randy Orrison]

>From the 4.3BSD (Mt. Xinu) open(2) man page:
|                        If the O_NDELAY flag is specified and
|    the open call would result in the process being blocked for
|    some reason (e.g. waiting for carrier on a dialup line), the
|    open returns immediately. The first time the process
|    attempts to perform i/o on the open file it will block (not
|    currently implemented).

Ok, so it's not currently implemented.  What happens?  If you open(2) a
file with O_NDELAY and then read from it, what happens?  I would guess
that the read wouldn't block, but what would it do?  (did i make my
question clear?)

Also, if a file is opened without O_NDELAY and the process blocks, can the
open be interrupted?  I notice in read(2) that a valid error return is EINTR,
but I don't see that for open(2).  Are opens uninterruptable?

What's the situation on System V?  (SVID/POSIX, too!)

	Thanks in advance!
		-randy

(Please reply to me, if there are requests i will summarize responses here)
-- 
Randy Orrison, Control Data, Arden Hills, MN
randy at ux.acss.umn.edu	{bungia, uunet!hi-csc, rutgers, sun}!umn-cs!randy
	"I consulted all the sages I could find in Yellow Pages,
	but there aren't many of them."			-APP