Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!rutgers!mcnc!ecsvax.uncecs.edu!dukeac!wolves!ggw
From: ggw@wolves.uucp (Gregory G. Woodbury)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: Filters (was ABE Source & introduction)
Summary: semantically equivalent forms
Message-ID: <1990Mar3.042312.12638@wolves.uucp>
Date: 3 Mar 90 04:23:12 GMT
References: <100765@looking.on.ca> <534@sixhub.UUCP> <333@comcon.UUCP> <334@comcon.UUCP> <335@comcon.UUCP> <103509@looking.on.ca>
Reply-To: ggw@wolves.UUCP (Gregory G. Woodbury)
Followup-To: comp.binaries.ibm.pc.d
Organization: Wolves Den UNIX BBS
Lines: 24

In article <103509@looking.on.ca> brad@looking.on.ca (Brad Templeton) writes:
>The concept of
>	type foo | tiny-dabe >abe.arc
>is silly.  It is not meant to be a filter in this manner.  You would use
>	tiny-dabe <foo >abe.arc

	Uhm, Brad.  These two forms are equivalent.
	There is a difference in that the computer doesn't have to do the
"type" explicitly, but the effect is the same.  The "<" symbol means that
the file named is connected to the "standard input" of the program and the
">" symbol says that the "standard output" of the program is to be redirected
to the named file.  The definition of a "filter" is that it accepts its input
on the "standard input" and produces its output on the "standard output".
	This, being the heart of the concept of toolmaking in programming,
allows a program to be more general and allows the user to combine the program
with others in a way that is not necessesarily forseen by the author of the
program.
-- 
Gregory G. Woodbury
Sysop/owner Wolves Den UNIX BBS, Durham NC
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