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From: jbn@wdl1.UUCP
Newsgroups: net.unix-wizards
Subject: Re: Re: how big is a pipe?
Message-ID: <725@wdl1.UUCP>
Date: Thu, 26-Sep-85 15:41:57 EDT
Article-I.D.: wdl1.725
Posted: Thu Sep 26 15:41:57 1985
Date-Received: Sun, 29-Sep-85 08:26:30 EDT
Sender: notes@wdl1.UUCP
Organization: Ford Aerospace, Western Development Laboratories
Lines: 11
Nf-ID: #R:brl-tgr:-166600:wdl1:64000018:000:492
Nf-From: wdl1!jbn    Sep 26 12:26:00 1985


     Approaches differ.  In AT&T's UNIX, a pipe is implemented as a circular
buffer in a file, normally four blocks long.  But if the pipe is reasonably
active the buffers never get written to the disk; all the action is in
the buffer cache.  In 4.2BSD, a pipe is a special case of a socket, and the
operation is performed entirely in memory.  In MS-DOS, a pipe is an illusion
created by the command interpreter; "p1 | p2" is implemented as 
"p1 > tmp; p2 < tmp; rm tmp".  

						John Nagle


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