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Re: asynchronous process management on WinWP; buffering problem?

From: Benjamin Riefenstahl
Subject: Re: asynchronous process management on WinWP; buffering problem?
Date: Sat, 15 Apr 2006 19:54:54 +0200
User-agent: Gnus/5.1001 (Gnus v5.10.1) Emacs/21.3.50 (gnu/linux)

Hi Lennart,

Lennart Borgman writes:
> It actually seems like is _isatty is defined in MinGW. I just tested
> a small program I found here:

The function isatty is defined in the Microsoft C runtime, and that is
what Mingw uses.  This version of isatty determines if a program is
running with stdin/stdout connected to an MS Windows console.

The way that consoles are implemented and used in MS Windows makes it
very complicated to use the console API to simulate a terminal in
Emacs.  On Unix-like systems this is done by so-called "pseudo-ttys",
"pty", but the MS Windows consoles are quite different beasts at the
OS API level.  Emacs would have to do a large amount of
reverse-engineering of the intent of the child process, to do with
consoles what Emacs does quite naturally on Unix with pseudo-ttys, and
there would still be features missing.  Therefore Emacs just uses
anonymous pipes instead which are a much better fit for the way Emacs
treats child processes, but that means that it can't make isatty in
child processes return true.

Cygwin can implement pseudo-ttys if it controls the parent as well as
the child, e.g. when you call a Cygwin program from a Cygwin compiled
Emacs.  It uses its own conventions to do that which are not
understood by non-Cygwin programs.

Sometimes you have a program that uses isatty to determine if it
should work in interactive mode or not, like the command shells of a
programming language or the some SQL interpreters.  In those cases you
will need to find a way put it into interactive mode without the help
of isatty.  Sometimes the shell will have a command-line option for
that, in other cases it can be configured after its start.


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