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From: gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>)
Newsgroups: net.unix,net.unix-wizards
Subject: Re: 4.2BSD Emulation on top of Sys V
Message-ID: <1751@brl-tgr.ARPA>
Date: Sun, 19-Jan-86 19:08:03 EST
Article-I.D.: brl-tgr.1751
Posted: Sun Jan 19 19:08:03 1986
Date-Received: Thu, 23-Jan-86 20:37:55 EST
References: <8424@ucla-cs.ARPA>
Distribution: net
Organization: Ballistic Research Lab
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Xref: watmath net.unix:6895 net.unix-wizards:16476

> BRL has a package that provides a System V emulation on top
> of 4.2BSD.  Has anyone written anything approximating a
> 4.2BSD emulation that runs on top of System V ?
> 
> If a complete emulation is not available, I am interested
> in subroutine libraries, macro packages, etc that help
> with porting programs from 4.2BSD to System V.

My feeling is that a sufficiently accurate user-mode emulation
of 4.2BSD along the lines of the BRL package is not feasible.
The terminal ioctls could be emulated moderately well, but
you can't get the right signal behavior, [gs]etre[gu]id(),
f*() system calls, etc.

One way to port programs from 4.2BSD to UNIX System V is to
edit the sources to work under the BRL package, and when the
work is done just move the files to the target system.  This
should also help with porting to other systems, too, since
the C and UNIX standards now being established look a lot
more like System V than like 4.2BSD.  If 4.nBSD (n > 3) does
not start looking more like System V Release N (N > 2), I am
afraid 4.nBSD's share of the UNIX world will dwindle to
insignificance.  That would put people who developed 4.nBSD-
specific applications into quite a bind.