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From:	culliton@srg.af.mil (Tom Culliton x2278)
X-Mailer: SCO System V Mail (version 3.2)
To:	rc@hawkwind.utcs.toronto.edu
Subject: Re: forking builtins
Date:	Fri, 24 Sep 1993 17:19:41 -0400
Message-Id: <9309241719.aa13919@ceres.srg.af.mil>

While this discussion about forking builtin's to do redirection is all
well and good, it seems like a fairly odd way to use read.  As I've said
in the past, the reasons you would usually use read are to:

1) Get a single line of input from a user.  In this case performance
isn't an issue and the user is presumably talking to fd 0 and there's no
problem.  (There may be a case for using /dev/tty but performance still
isn't going to be an issue.)  For example:

	echo -n 'Where do you want logfile written? '
	read logfilename

2) Chewing through a whole input stream or datafile.  In this case
performance is an issue but since the data is presented as a stream
presumably on fd 0 and again there's no problem.  For example:

	here = `pwd { find . -type d -print | while (read dirname) {
	 if (cd $here/$dirname) ls -l >.contents }}

I can only think of one case where you might do something like (get only
the first line of a file):

	read bgcolor <.background

and in that case you'd be crazy to do it more than once, so again
performance shouldn't be an issue.

Tom