Path: utzoo!mnetor!tmsoft!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!wuarchive!udel!haven!adm!news
From: cschmidt@lynx.northeastern.edu
Newsgroups: comp.lang.pascal
Subject: re: Change ENV.
Message-ID: <25885@adm.brl.mil>
Date: 8 Feb 91 12:59:55 GMT
Sender: news@adm.brl.mil
Lines: 23

There was some discussion a while back about writing a program that
accesses the DOS environment of the parent or root process.
Techniques were presented for tracing back through the chain of PSPs
to find the root PSP, then using the value at offset $2C in the root
PSP as the segment address of the root copy of the DOS environment.

Turns out that in Tandy DOS version 03.10.01 the root PSP contains the
value zero at this offset.  I have discovered by inspection that the
root environment is stored in the DOS memory block directly following
the DOS memory block that contains the root PSP.  I can use this fact
as a workaround in the case when $2C contains zero.

(When a secondary copy of COMMAND.COM is loaded, that copy's PSP
contains the correct segment address of its copy of the environment.)

Are there any other versions of DOS that store zero at offset $2C in
the root PSP?  Can I be confident that by employing the workaround
described above, my programs will work with all versions of DOS?

I will summarize to the net replies received by mail.

Christopher Schmidt
cschmidt@lynx.northeastern.edu