Can anyone send us info. on multiplex files?

[chris at umcp-cs.UUCP]

*	From: bsafw at ncoast.UUCP

	Our installation (running Microsoft Xenix 1.03.02 ...) is
	capable of using multiplex files...

But have they fixed the bugs that cause the system to crash and the
disks to be corrupted if you use them?

Perhaps that's why they didn't include documentation....

I'm not sure what the system call index number is, but the names
in the C library are ``mpx'', ``chan'', ``extract'', ``attach'',
``detach'', and ``connect''.  (They all go through a common syscall
vector.  There are some more names but they aren't generally very
useful.)  ``mpx'' creates multiplexed file nodes, ``chan'' creates
a channel, ``attach'' attaches a channel to an mpx node, ``detach''
removes a channel from an mpx node,  ``extract'' gets a file
descriptor to a channel, and ``connect'' allows you to connect TTYs
to the mpx file.

There are a huge number of magic things that can happen on MPX
files (M_WATCH, M_BLK, MXNBLK mode, ...), of which perhaps most
work if you use them very carefully.

Closing mpx nodes tends to hit the kernel bug and lose files,
directories, etc.  There is a race condition in which the inode
gets freed twice.

To sum up:  if you can possibly do so, use PTYs rather than MPX
files.

(Does anyone know if sending mpx(2)/mpxio(5) manuals would violate
copyright laws?)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci (301) 454-7690
UUCP:	{seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet:	chris at umcp-cs		ARPA:	chris at maryland