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From: brandon@tdi2.UUCP (Brandon Allbery)
Newsgroups: comp.unix.wizards
Subject: System V job control idea
Message-ID: <337@tdi2.UUCP>
Date: Sun, 12-Apr-87 19:11:24 EST
Article-I.D.: tdi2.337
Posted: Sun Apr 12 19:11:24 1987
Date-Received: Tue, 21-Apr-87 03:46:53 EST
Reply-To: brandon@tdi2.UUCP (Brandon Allbery)
Distribution: world
Organization: Tridelta Industries, Inc., Mentor, Ohio
Lines: 20

Recently it occurred to me that there exists a form of simple job control
under every version of UNIX since the Seventh Edition (at least).  It's
called ptrace().

A shell could fork a child which does a ptrace(0) then execs the intended
target program.  The parent (after continuing the child from the SIGTRAP
stop caused by the exec) then can wait() for the child; SIGQUIT (for example)
can be usurped as the stop character and used by the shell as a special
case for continuation.

Aside from the inhibition of setuid (which should be reconsidered for this
application, maybe; what kind of ``fraud'' is it designed to prevent?), are
there any reasons this won't work?  (I know, no SIGTTIN/SIGTTOU.  Oh well.)

++Brando
-- 
Brandon S. Allbery	           UUCP: cbatt!cwruecmp!ncoast!tdi2!brandon
Tridelta Industries, Inc.         CSNET: ncoast!allbery@Case
7350 Corporate Blvd.	       INTERNET: ncoast!allbery%Case.CSNET@relay.CS.NET
Mentor, Ohio 44060		  PHONE: +1 216 255 1080 (home) +1 216 974 9210