From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from oldp.astro.wisc.edu ([128.104.39.15]) by hawkwind.utcs.toronto.edu with SMTP id <2645>; Mon, 7 Jun 1993 13:10:26 -0400
Received: by oldp.astro.wisc.edu (5.65/DEC-Ultrix/4.3)
	id AA08381; Mon, 7 Jun 1993 12:10:17 -0500
Message-Id: <9306071710.AA08381@oldp.astro.wisc.edu>
To:	haahr@mv.us.adobe.com (Paul Haahr)
Cc:	rc@hawkwind.utcs.toronto.edu
Subject: Re: redirection and built-ins 
Date:	Mon, 7 Jun 1993 13:10:16 -0400
From:	Alan Watson <alan@oldp.astro.wisc.edu>
X-Mts: smtp

Paul writes:
> it's inappropriate because rc already has a perfectly good
> mechanism for setting variables to the output of commands:  backquotes.
> why is that not enough?  what functionality does that lack?

Oh, the ability to encapsulate the process in a function (yes, I know
that in es one could pass a program fragment, but this is the rc-list
after all), and an easy way to get at the return value (yes, I know
that may be fixed in a later version, but I'd still rather hide the
grubby details in a function).

> what does this mean?  (``functionally-implemented''?  that it works?
> that it doesn't have side effects?)

It means `implemented as a function'.

> the mechanism we came up with for doing this [redirection on 
> built-ins without forking] in
> es could be applied to rc just fine, but it seems like a lot of
> work for very little payoff.

Fine.  I'm prepared to accept that answer; as I said in my original
message, I'm only interested in exploring the possibilities, and I am
not campaigning for either of these changes.  I'm not concerned about
the performance aspects, only the functionality.

> what should happen if the command is
> 	exit 1 | exit 2 | exit 3
> ?  

There will always be pathological cases: even now, if you have an exit
in a function and run it with and without redirection, different things
happen.  I haven't heard of anyone losing any sleep about it.