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From: karl.kleinpaste@osc.edu
Newsgroups: comp.unix.shell
Subject: Re: what shell do I have?  job-control
Message-ID: <1991Apr19.210430.3527@oar.net>
Date: 19 Apr 91 22:03:08 GMT
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clewis@ferret.ocunix.on.ca writes:
   >And of course there's job control.  Actually again and again I hear
   >that this is an invention of C shell, but as recently as last year in
   >spring I still had a csh w/o this.

   Few System V versions of UNIX have job control in their csh's because
   the kernel support for it is (was) a BSD-only-ism and rarely present.

Most SysV vendors should be flogged over the head with a listing of
the ancient csh source they use in their distributions.  A couple
things about it...

Most csh incantations distributed with SysVRel[0-3] are derived from
(something like) the 2.8BSD PDP-11 distribution, circa 1982 or
thereabouts.  This csh was rather primitive (some would say "primitive
csh" is redundant, and they might be right) in that it pre-dated the
releases of BSD with VM, job control, the new tty driver, and all that
rot.  It'll compile straight on a real V7, possibly even V6, PDP-11
because it expects no peculiar functions at all.  This is why it's
nice-n-easy to bring along on SysV.  Unfortunately, it also lacks a
number of the nicer things csh has gained over the years, such as the
dir stack, the eval builtin, and the $< pseudovariable.  So if you
mumble "dirs" at your Microport or SCO csh, it'll probably complain,
"Command not found."

That said, I'll assert, for the N+1st time, that it's possible to
emulate a hefty fraction of BSD-style job control under SysV using
ptrace(2).  It's do-able, and livable; I've done it and lived under it
for 3+ years when working for AT&T with only SysV for an environment.
I hadn't touched it in a couple of years since leaving AT&T, but found
cause to clean up a few warts here and there in just the last couple
of days, for the sake of someone bringing it up again on cblpn.att.com.

--karl