Date: Fri, 29 Jun 2001 21:53:10 +0300
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
Sender: halo1 AT zahav DOT net DOT il
To: Jonathon Merz <jmerz42 AT earthlink DOT net>
Message-Id: <6923-Fri29Jun2001215309+0300-eliz@is.elta.co.il>
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CC: djgpp AT delorie DOT com
In-reply-to: <3B3CADA3.4000506@earthlink.net> (message from Jonathon Merz on
	Fri, 29 Jun 2001 11:32:35 -0500)
Subject: Re: Incorrect resolution of COMSPEC environment variable on WinNT
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> Date: Fri, 29 Jun 2001 11:32:35 -0500
> From: Jonathon Merz <jmerz42 AT earthlink DOT net>
> 
> Is this a bug or am I missing something?

You are missing something ;-)

> main()
> {
>     char *comspec_value = getenv("COMSPEC");
>     printf("%s\n", comspec_value);
> }
> 
> When compiled with DJGPP's gcc on WinNT 4, the output is:
> 
> C:\WINNT\SYSTEM32\COMMAND.COM
> 
> The trouble is that on NT 4, (and I have verified this in my shell) COMSPEC is 
> set to c:\winnt\system32\cmd.exe.  The correct value is output when compiled 
> under several other compilers.

This is a ``feature'' of Windows NT: when a DOS program runs, it gets
COMMAND.COM as the value of COMSPEC in its environment, even if
outside the program COMSPEC has a different value.  Windows NT doesn't
want DOS programs to think they are on Windows, it pretends to be DOS.

Likewise, all the names of important (or maybe all, I forget)
environment variables are up-cased when they are passed to DOS
programs.  Thus, Path is converted to PATH, ComSpec is converted to
COMSPEC, etc.

There's nothing (AFAIK) a DOS program can do to avoid this, because
this behavior is entirely inside the NT DOS emulator.

However, why is this a problem in your case?  DOS programs in general
and DJGPP programs in particular should not normally care about this.

> if there is a way to identify the operating system the program is
> running under

It's not easy.  For example, there's no easy way we know of to
distinguish NT from Windows 2000.  But if you don't care about the
difference, call _get_dos_version(1), and if it returns the version
5.50, you are on NT.