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Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!ittatc!dcdwest!ncr-sd!greg
From: greg@ncr-sd.UUCP (Greg Noel)
Newsgroups: net.unix
Subject: Re: /bin/true
Message-ID: <469@ncr-sd.UUCP>
Date: Fri, 2-May-86 16:36:05 EDT
Article-I.D.: ncr-sd.469
Posted: Fri May  2 16:36:05 1986
Date-Received: Sun, 4-May-86 05:30:23 EDT
References: <481@batcomputer.TN.CORNELL.EDU> <518@looking.UUCP> <2437@teddy.UUCP> <142@myab.UUCP> <765@bentley.UUCP> <401@brl-smoke.ARPA>
Reply-To: greg@ncr-sd.UUCP (Greg Noel)
Organization: NCR Corporation, San Diego
Lines: 40

In article <401@brl-smoke.ARPA> gwyn@brl.ARPA writes:
>[The true and false commands] main use is to hang system-type links on.
>For example, on the system I'm typing this on, "gould" is linked to "true"
>and other system types such as "vax" are linked to "false".  These commands
>are very useful if you maintain code for multiple systems all in the same
>place.

Well, I admit that doing it that way is better than nothing, but I've been
in the same environment and I've always considered it a bit of a misfeature.
The problem is one of future compatibility -- if you add a new machine type,
you have to put in a link on every machine in the world.  A better scheme
would have been a single command, say "machid", that only consisted of the
command "echo gould".  Then, the usual sequence of:
	if pdp11; then ...
	elif vax; then ...
	elif pyr; then ...
	elif gould; then ...
	elif tower; then ...
	elif sequent; then ...
	elif amiga; then ...
	elif telefunken; then ....
	else echo "I don't know how to handle this machine"; fi
(an exageration, admittedly, but do \you/ have links for all those machines?)
becomes:
	case `machid` in
	pdp11)	... ;;
	vax)	... ;;
	pyr)	... ;;
	gould)	... ;;
	tower)	... ;;
	sequent) ... ;;
	amiga)	... ;;
	telefunken) ... ;;
	*)	echo "I don't know how to handle machine-type `machid`" ;;
	esac
This is no more difficult to manage, and easy to extend compatibly.  And if
you don't have a link for "telefunken" then it doesn't cause your makefile
to punt.......
-- 
-- Greg Noel, NCR Rancho Bernardo    Greg@ncr-sd.UUCP or Greg@nosc.ARPA