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X-Authentication-Warning: slinky.cs.nyu.edu: pechtcha owned process doing -bs
Date: Thu, 3 Apr 2003 21:47:06 -0500 (EST)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: Steven Kilby <skilby AT visionsolutions DOT com>
cc: cygwin AT cygwin DOT com
Subject: RE: Pipe behavior
In-Reply-To: <D0720E03FE8450489330A332BDB176430102DD89@exchange.visionsolutions.com>
Message-ID: <Pine.GSO.4.44.0304032145290.21921-100000@slinky.cs.nyu.edu>
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Steven,

Perhaps because your program isn't the only one buffering its stdout...
Has it occurred to you that "cat" might too?
	Igor

On Thu, 3 Apr 2003, Steven Kilby wrote:

> Randall,
>
> Thanks for the response.  No, I am not sure that Emacs uses pipes
> instead of ptys.  I'll have to look at that.  I was testing with the
> cygwin character emacs.  What you said makes sense but I have one more
> question.  I modified the code by inserting a call to fflush between the
> printf's.  I would have thought this would force the first printf to
> display immediately but this did not happen.  Can you help me understand
> why?
>
> Thanks
> Steven
>
> -----Original Message-----
> From: Randall R Schulz [mailto:rrschulz AT cris DOT com]
> Sent: Thursday, April 03, 2003 4:41 PM
> To: cygwin AT cygwin DOT com
> Subject: Re: Pipe behavior
>
> Steven,
>
> At 16:28 2003-04-03, you wrote:
> >Hello,
> >
> >I have a question about pipe behavior.  I wrote a simple program that
> >does a printf, sleeps for 5 seconds and then another printf.  If I run
> >the program with the following way:  $ ./simple | cat  The output is
> >delayed until the program finished.  I guessed that the pipe is
> >buffered and doesn't flush until it is closed when the program ends.
> >But then I ran the same program as an emacs subprocess and attached a
> >buffer to it. In this scenario the first printf is displayed, 5 seconds
> >pass and then the second printf is displayed.  Emacs also uses pipes so
> >I do not understand why the behavior is different.
>
> Pipes don't buffer in the manner you describe, but the standard I/O
> library does when its output is directed to a pipe or a plain file.
>
> Are you sure that Emacs uses pipes and not ptys (pseudo-ttys)?
>
> Which Emacs are you using? Cygwin or Windows?
>
> >Thanks
> >Steven Kilby
>
> Randall "We don't need no stinkin' disclaimers" Schulz

-- 
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ZZZzz /,`.-'`'    -.  ;-;;,_		igor AT watson DOT ibm DOT com
     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski
    '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!

Knowledge is an unending adventure at the edge of uncertainty.
  -- Leto II


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