UNIX System V on top of 4.2BSD

[gwyn%brl-vld at sri-unix.UUCP]

From:      Doug Gwyn (VLD/VMB) <gwyn at brl-vld>

In order to handle the volume of inquiries, I am posting a description
of the BRL UNIX System V user/programmer environment for 4.2BSD to the
mailing list.  This is not a commercial offering, it continues to
evolve, and I hope that only people with a genuine need will ask for
the package since I am not budgeted for software distribution.  There
is a chance that some 4.2BSD packaged system vendors or support
organizations will eventually provide something like this package with
full support.  It would also be nice if the two main UNIX familes would
stop diverging, at least at the user/programmer level.


The basic idea of this package, which is in the public domain subject
only to Western Electric UNIX System V licensing restrictions, is:

The user/programmer on a 4.2BSD system who desires a UNIX System V
environment sets his $PATH to something like:
	PATH=/usr/5bin:/bin:/usr/bin:/usr/ucb:/usr/local:.
The directory /usr/5bin contains a rather complete set of UNIX
System V utilities (SCCS, PWB/Graphics, and the usual programs); the
language processors have been modified to find #include files in
/usr/include5 and libraries in /usr/5lib.  The heart of the emulation
is a compatibility C library, /usr/5lib/libc.a.  This library attempts
rather successfully to emulate the behavior of real UNIX System V C
library routines, including system calls, as accurately as could be
accomplished efficiently, even down to the errno codes.  As far as a
programmer operating in this environment is concerned, he is using
UNIX System V (with bug fixes, modernized cxref, and "classes").

User utilities such as "ps" that didn't make much sense to adapt to
the Berkeley system have been omitted from /usr/5bin, so the user
gets the distributed 4.2BSD version of such things.  The roughest
spot is the use of Berkeley object module format, since the kernel
doesn't know how to exec UNIX System V objects; this forced adoption
of the Berkeley "as", "ld", and "ar" (complete with "ranlib", ugh)
instead of UNIX System V Common Object File Format.  This could
perhaps be fixed by someone who wants to hack on the Bell "ld",
but I didn't feel it was necessary for normal use.

Terminal ioctl() is emulated remarkably well, considering how
different the Bell and Berkeley terminal drivers are.  I did not
try to provide Bell-style IPC or FIFOs, since efficient emulation
of these facilities would require kernel changes.  The overriding
rule when developing this package was to NOT CHANGE THE BERKELEY
SYSTEM; apart from a couple of bug fixes involving SIGCHLD and a
replacement Bourne shell (upward-compatible), the UNIX System V
package installation consists merely of ADDING directories to the
system.  I also didn't provide X.25 or KMC support, which require
kernel work, nor RJE, mail, or UUCP, which a Berkeley system will
probably provide its own facilities for.  It is easy enough to
compile UNIX System V sources to provide anything I omitted that
you need to have; the only real glitches may be embedded pathnames
and accessing directories (for the latter, I have included
Berkeley-style directory access routines in the C library).

In general, it is not wise to attempt to mix 4.2BSD and UNIX System
V modes.  I did provide all the incompatible Berkeley system calls
in the C library, using names beginning with an underscore (e.g.,
_gethostbyname()), just in case you need them; mostly these were
intended for use in compatibility C library routines (for example,
ioctl() calls on _ioctl()).  Although I had to lengthen C variable
names to support some of the Berkeley kernel calls, I did not extend
the name length very far (limit 16 chars) and "lint" will definitely
complain about long identifiers (as it SHOULD; they violate the C
language standard).  "cpp" has an option to permit redefining really
long symbols if required in order to adapt code from a Berkeley system.

You can get this package "free" by sending the following:
	xo  Copy of the relevant pages of your UNIX System V license
	   (either source or binary, although source is recommended)
	xo  Statement of desired tape density (1600 bpi default)
	xo  A reel of magtape (1200' is sufficient at 1600 bpi)
	xo  Your return mailing address
	xo  If you prefer to wait for the 4.2BSD version (we are
	   running 4.1cBSD until our 4.2BSD tape arrives), you
	   should so state; otherwise you get a copy of whatever I
	   have when I write the tape
to the following address:
	Douglas A. Gwyn
	U.S. Army Ballistic Research Lab.
	DRSMC-BLV-V
	Aberdeen P.G., MD 21005

	(301)278-6647
	gwyn at brl-vld.arpa or {decvax,esquire,unc}!brl-bmd!gwyn

Effective use of this environment requires that you have UNIX System
V user documentation; although /usr/5bin/man does know how to print
the appropriate manual pages, users still need printed manuals.  Of
course I am not in a position to offer support, although I accept bug
reports and gradually evolve the package, since we do use it ourselves.