Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ico!nbires!maa
From: maa@nbires.nbi.com (Mark Armbrust)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Redirect > nul affects procomm, why?
Summary: TSR doesn't close files.
Message-ID: <427@nbires.nbi.com>
Date: 18 Jul 89 16:22:16 GMT
References: <24c29f1b@ralf>
Reply-To: maa@nbires.UUCP (Mark Armbrust)
Organization: NBI Inc, Boulder CO
Lines: 17

In article <24c29f1b@ralf> Ralf.Brown@B.GP.CS.CMU.EDU writes:
>
>It seems that DOS doesn't close open files when a program goes TSR.  Since the
>">NUL" redirection opens a file for the duration of the program, that file
>stays open after the program goes TSR (files ARE closed on non-TSR
>termination).

I just looked at my 3.30 disassembly, this is indeed true.  I'd guess that the
rationale for this was that the TSR was going to use the files later in its
life.  There's only one problem with this -- MS didn't tell programmers how to
save/change/restore the PID within the TSR so that it could use these files
that were so [in]conveniently left open!
-- 

Mark Armbrust
maa@nbires.nbi.com
maa@nbires.UUCP