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RE: Pipe behavior


Steven,

I assume the test program you're using to explore this behavior is pretty concise. Why don't you post it here?

Randall Schulz


At 16:44 2003-04-03, 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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