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From: hamilton@uiucuxc.CSO.UIUC.EDU
Newsgroups: net.micro.pc
Subject: Re: where are you after a batch file
Message-ID: <21900112@uiucuxc>
Date: Wed, 12-Feb-86 03:27:00 EST
Article-I.D.: uiucuxc.21900112
Posted: Wed Feb 12 03:27:00 1986
Date-Received: Fri, 14-Feb-86 07:43:24 EST
References: <440@tekig5.UUCP>
Lines: 32
Nf-ID: #R:tekig5.UUCP:440:uiucuxc:21900112:000:1795
Nf-From: uiucuxc.CSO.UIUC.EDU!hamilton    Feb 12 02:27:00 1986


>> Now, a suggestion: why doesn't somebody write a program that either (a) keeps
>> the directory stack in the environment, instead of having to have a writeable
>> file sitting around on disk and doing disk accesses for directory
>> pushing/popping?
>
>[this] is a great idea, but I've never seen anybody propose a method
>for handling this.  You have to remember that when a program is run by
>DOS, it is given a COPY of the original environment.  You can write a
>program to modify that environment (though it is still unclear how you
>know how much space that environment has been allocated, as opposed to how
>much it is using).  You could even use Microsoft C 3.0's builtin functions
>for doing this.  But when your program exits the old environment will be
>restored with none of your changes.

well, there is an ugly way to do this (modify command.com's copy of the
environment).  i did some exploring some time back, and figured how to
scan memory and recognize memory control blocks.  you can also find out
where command.com is (the para is all you want) from one of the several
pointers to it in your psp.  the first memory control block before the
one containing command.com (if i remember right) is the one containing
command.com's environment (i _said_ it was ugly).  the control block
tells you how much space is allocated to the environment, and you parse
to find how much was used.  i wrote a little program using a scan for
control blocks to produce a map of allocated memory; the result is
slightly useful as a substitute for a "ps".

	wayne hamilton
	U of Il and US Army Corps of Engineers CERL
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