Path: utzoo!yunexus!maccs!cs3b3aj
From: cs3b3aj@maccs.McMaster.CA (Stephen M. Dunn)
Newsgroups: comp.sys.ibm.pc
Subject: Re: MS-DOS puzzle #1
Summary: too lazy to write it in
Keywords: stdin stdout stderr redirection
Message-ID: <2515@maccs.McMaster.CA>
Date: 23 Apr 89 03:46:27 GMT
Article-I.D.: maccs.2515
References: <6893@bsu-cs.bsu.edu>
Reply-To: cs3b3aj@maccs.UUCP (Stephen M. Dunn)
Organization: McMaster U., Hamilton, Ont., Can.
Lines: 25

In article <6893@bsu-cs.bsu.edu> dhesi@bsu-cs.bsu.edu (Rahul Dhesi) writes:
>     Question:  Why does COMMAND.COM allow redirection of standard
>     input and standard output, but not standard error?

   As I understand it, when you say "<", MS-DOS closes file handle 0 (STDIN)
and then opens the file you specified.  Since it uses the lowest available
handle, it ends up redirecting STDIN.  Ditto for STDOUT redirection.  (This
explanation condensed from _Advanced MS-DOS_, Ray Duncan, Microsoft Press).

   Why can't you redirect STDERR (or, for that matter, STDAUX or STDPRN)?
Because they didn't write in a facility as in *NIX so that you could
specify the handle number to be redirected.  Why?  Probably because they
(read the powers that be at Microsoft, not the guys who coded it) figured
there wasn't enough demand for this feature to justify writing it.

   I can't see that it would take that much extra code to implement *NIX-
style redirection of any handle, but to be honest, I've never needed to
redirect anything other than STDIN or STDOUT (I'm not saying there's no
need to do so, just that I've never needed to do so).

-- 
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! Stephen M. Dunn, cs3b3aj@maccs.McMaster.CA ! DISCLAIMER:           !
! Goddamn exams!  I hate them!  I hate them! ! I'm only an undergrad !
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