Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!virtech!cpcahil
From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.unix.questions
Subject: Re: Why does pipeline work this way?
Summary: because stdout output is buffered
Keywords: pipeline, grep | cat
Message-ID: <1989Dec16.133416.3855@virtech.uucp>
Date: 16 Dec 89 13:34:16 GMT
References: <10064@saturn.ucsc.edu>
Organization: Virtual Technologies Inc.
Lines: 21

In article <10064@saturn.ucsc.edu>, ray@saturn.ucsc.edu (Ray Swartz) writes:
> Yet, when I run grep by itself, the output comes out to the tty as soon
>  as grep finds a line.  Why is it that when grep prints to a terminal
> the output appears unbuffered and when it is going into a pipe, it
> appears buffered?

Grep writes it's matches to stdout which is buffered by line on output
to a terminal and buffered by data block on any other output medium, including
pipes.

If you really want this functionality, get the gnu grep sources and add
a parameter to stop looking after the first match (i.e. only show the
first matching record).  Or you could make it reall inefficient and turn
off all buffering, but I don't recommend this.


-- 
+-----------------------------------------------------------------------+
| Conor P. Cahill     uunet!virtech!cpcahil      	703-430-9247	!
| Virtual Technologies Inc.,    P. O. Box 876,   Sterling, VA 22170     |
+-----------------------------------------------------------------------+