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RE: shell and output redirection

From: <Ganesh.Raja_at_barclayscapital.com>
Date: Fri, 2 Jul 2004 21:26:57 +0100
Message-ID: <34D7360B56EFC0428F83565A3E1880E8F4BE38@LDNPSMEU002VEUA.INTRANET.BARCAPINT.COM>


That should have been "NoT DOES TWO PROCESSES IN PARALLEL...

:)

Cheers,
Ganesh R

-----Original Message-----
From: Ganesh.Raja_at_barclayscapital.com
Sent: 02 July 2004 21:20
To: oracle-l_at_freelists.org
Subject: RE: shell and output redirection

I was quite stunned to Know that is wahat happened.. I always tHought that Pipes as the Nomal "|" does two Process Parallely ... Something new Learnt ... :)

Cheers,
Ganesh R

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Tanel P=F5der
Sent: 02 July 2004 21:18
To: oracle-l_at_freelists.org
Subject: Re: shell and output redirection

> Programs are executed simultaneously. Pseudocode goes like this:=20
> create pipe fork process 1 {
> open pipe for output
> exec program 1 }
> fork process 2 {
> open pipe for input
> exec program 2 }

Ok, but if program 1 will issue a write request to the pipe now, shall it post process 2 and not continue before process 2 has completed?

As I saw from your trace, shell uses pipe() to create the pipe file descriptors for passing on data between processes. What if I create a pipe manually using mknod and run my two processes manually, does the data streaming work exactly the same way that with shell-generated pipe?

Tanel.



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Received on Fri Jul 02 2004 - 15:23:50 CDT

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