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From: bc@cyb-eng.UUCP (Bill Crews)
Newsgroups: net.micro
Subject: Re: Help with MS-DOS
Message-ID: <540@cyb-eng.UUCP>
Date: Tue, 23-Apr-85 09:16:51 EST
Article-I.D.: cyb-eng.540
Posted: Tue Apr 23 09:16:51 1985
Date-Received: Fri, 26-Apr-85 21:47:58 EST
References: <10051@brl-tgr.ARPA> <1700@watcgl.UUCP>
Organization: Cyb Systems, Austin, TX
Lines: 29

The deal is that you are working with the child process's environment,
which was set up as a copy of the parent's environment when the child
was forked.  There are probably several ways to solve your problem; what
comes to mind is that two undocumented DOS function calls (things you get
at with int 21h) not only get the segment address of the current psp
(program segment prefix) but can also *set* (think on this!) a psp as
being the current psp . . . like, multitasking, huh?  These are functions
51h and 50h respectively.  You could get the current psp and save it,
set your parent's psp as current (communicating your parent's psp to the
child is comething you must take care of some way or another) and then
access the environment.  You will be accessing the parent environment.

Be aware, however, that you have actually set the parent to be the current
process, so any files you might open will belong to the parent, *not* the
child!  So be careful to set the psp back to the child before continuing.

There may be an easier way, but I can't think of it offhand.  By the way,
I don't warrant the use of functions 50h and 51h -- I just use them and
they seem to work.

Good luck.

-- 

  /  \    Bill Crews
 ( bc )   Cyb Systems, Inc
  \__/    Austin, Texas

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