Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!aurora!labrea!agate!ucbvax!RSBS0.anu.OZ.AU!STRASSER
From: STRASSER@RSBS0.anu.OZ.AU (Mike Strasser)
Newsgroups: comp.os.vms
Subject: Odd subprocess behaviour
Message-ID: <8802071211.AA08083@uunet.UU.NET>
Date: 7 Feb 88 22:02:53 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 38

I have noticed two odd piecess of behaviour in handling subprocesses,
which I think shouldn't happen.  Both happen under VMS 4.6, on both an
11/750 and a 8700 (it *should* be consistent!).

Firstly, if you create a subprocess and attach to it, then re-attach to
the parent process, then spawn a second subprocess and attach to it, THEN
kill the first subprocess with a STOP command from t'other (still with
me?), VMS can't decide which of the remaining two processes (parent and
2nd child) is attached to the terminal!  You get a mixture of prompts, and
it isn't clear where the things you type go.

Why would I be doing this?  Well, I often run a program in my login process,
then spawn a child to do a few other things.  One program I use keeps that
child intact even after it exits (all right, I wrote it that way deliberately)
so in a later run of the program (which I use frequently) I can jump into
the same child process (which is given a particular name by the program).
This saves time with creating and killing processes (fast on the 8700 with
< 30-odd users, and always slow on the 750).  I have a subprocess quota of
2 on both machines, and a couple of times I've been in another child 
process created by a different program and I've wanted to kill the first so
I could create another for something else.  Simple, really!  Anyway, my
point is that VMS shouldn't be behaving this way.  Anyone else seen this?

My second observation is that whenever you leave a child process (logout or
attach), that last command line (logout or attach...) is put 
on the top of the command stack of the parent process if it's running a
program, but not at DCL level.  Anyone explain why this should be so?  To
give an example, this happens from TPU.

Mike Strasser

Research School of Biological Sciences
The Australian National University
Canberra, Australia

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