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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.std.unix
Subject: Re: tar vs. cpio
Message-ID: <8362@ut-sally.UUCP>
Date: Tue, 23-Jun-87 20:56:16 EDT
Article-I.D.: ut-sally.8362
Posted: Tue Jun 23 20:56:16 1987
Date-Received: Tue, 30-Jun-87 06:46:55 EDT
References: <8188@ut-sally.UUCP> <8208@ut-sally.UUCP> <8249@ut-sally.UUCP>, <8276@ut-sally.UUCP>
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Reply-To: henry@utzoo.UUCP (Henry Spencer)
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Approved: jsq@sally.utexas.edu (Moderator, John Quarterman)
Summary: Cpio format makes correct handling of links impossible, too.

From: henry@utzoo.UUCP (Henry Spencer)

As a counterpoint to Kenneth Almquist's example of tar fouling up links,
try the following:

	echo hi >one
	ln one two
	ls one two | cpio -o >/tmp/foo
	rm one two
	cpio -i one </tmp/foo
	cpio -i two </tmp/foo

Now we have cpio creating two files where there was supposed to be only one
with two links.  Note that tar would get this one right!  (Although you would
have to be careful to get the order right, admittedly a wart.)

The moral of the story is that it is very hard to handle links properly in
a format like tar or cpio, and *neither* of the existing formats is bullet-
proof in the presence of links.  This is not a valid argument for or against
either format; they merely screw up in different ways.  One can argue about
the relative probabilities of the different screwup types causing trouble,
but I think the point is made.

				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry

Volume-Number: Volume 11, Number 79