ultrix 2.0 _iob storage

[Chris Torek]

In article <575 at jim.odr.oz> jon at jim.odr.oz (Jon Wells) writes:
>[attempt two, sorry if you've seen this before, I may have messed
>up the posting, anyway, I didn't get any response and I'd like to know]

(I saw a response, but anyway...:)

>[found code that reads]
>for ( p = &_iob[3]; p < _iob[nfiles]; p++ )
>	fclose(p);

>You can't do this with ultrix (2.0) as _iob is only 3 slots long, all
>other struct _iobuf's are allocated dynamically so &_iob[3]....
>just points off into the weeds.

The same is true in 4.3BSD, except that NSTATIC _iob's exist.  NSTATIC
happens to be 20.

>Is the above code deemed to be a reasonable way of doing this?

No.

>Ultrix provides a function called _fwalk() ....

Also found in 4.3BSD.  (Guess which group invented it. :-) )

>Is _fwalk() standard on other genders of unix???

No.

>Or is there a much better way of closing everything but stdin etc.????

No.  What you can do in the presence of a dpANS-conformant system is this:

	(void) fflush((FILE *)NULL);
	for (fd = 3; fd < nfiles; fd++)
		(void) close(fd);

which leaves the FILEs open but closes the underlying descriptors, after
pushing any pending output.  If you are about to exec()---this is the
only reasonable use for the above---it will work.  But nobody handles
fflush(NULL) yet.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris