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From: gnu@hoptoad.uucp (John Gilmore)
Newsgroups: comp.sys.ibm.pc
Subject: Re: ARC/ZOO/TAR
Message-ID: <3456@hoptoad.uucp>
Date: Thu, 3-Dec-87 07:59:11 EST
Article-I.D.: hoptoad.3456
Posted: Thu Dec  3 07:59:11 1987
Date-Received: Mon, 7-Dec-87 01:22:28 EST
References: <3027@umn-cs.cs.umn.edu> <617@omen.UUCP>
Organization: Nebula Consultants in San Francisco
Lines: 69

I don't normally read comp.sys.ibm.pc, but a friend pointed me at the
discussion of PD tar here.

Mostly tar was designed to run on larger systems, and to be compatible
with the Unix tar program.  When the Unix Standards effort (POSIX)
looked reasonable enough to pick tar as a standard tape format, it was
also intended as an easy way to read/write that format.  Now it looks
like the marching morons on the committee will end up picking cpio because
it's System V specific, so tar is just for the folks who want a good
tar program.  It was ported to MSDOS by Mike Rendell (uunet!garfield!michael)
and I rolled his changes back into the mainline sources for the release.

Chuck Forsberg said that tar had a "shortcoming" that "compression
wasn't built in".  I see how people on MSDOS are forced to build tools
that do everything by hand (e.g. compression, searching for files, etc)
but I do not build things that way.  Since my tar is truly public
domain, you can take it and hack in the guts of compress somehow, but I
will not take the changes back.  Tar and compress are perfectly good
tools, like a hammer and a chisel.  I don't want to build a "hasel", I
like them separate.  If your OS and/or shell can't manage to connect
two perfectly good tools, I guess you had better go build yourself a
hasel.

This problem is rampant on MSDOS and I wish you all luck in getting
past it without throwing all your software away.  Somehow I don't think
OS/2 will be it, given Microsoft's past taste in software and current
partnership with the biggest hardware company and the worst software
company.  But it's hard for me to run down an undocumented, unreleased
system (except for its being announced with no doc and no release).

Someone said tar doesn't write directory ownership, permission, etc.
He's using an ancient tar program.  Mine does, as does Berkeley's and
the one spec'd by POSIX.  It *does* archive empty directories, too.
It can read tar archives with or without directories (old or new).
Chuck also complained that there is no apparent standard for tar.
When I started writing it, I followed up every case I heard of (on the net
and off it) of people not being able to read tar tapes from some other
system.  The two problems I found were:  Some systems write tape blocks
larger than other systems' tape drives can read; and: some minor systems
write their tapes out byte swapped because the idiot who programmed
the driver didn't notice and then was too lily-livered to admit it was
a bug.  In short, there are no compatability problems with tar.  People
with old tar's can read the output of mine, and the worst they get is
a few error messages.

One thing Chuck mentioned that I *would* like to support is multiple
volumes (floppies or tapes) but I want to do it such that:

	* You can read back any subset of the volumes, as long as
	  they contain the data you want.  You don't have to start
	  from #1 and go to #N.

	* You don't have to tell tar "how big" a volume is.  This
	  doesn't work on any kind of tapes -- how much fits depends
	  on how many errors occur, how often the tape stops, etc.

	* The design is reasonable enough that Unix tar's will pick it
	  up.

I've heard that DEC has done a multi-volume tar in their newest Ultrix
release, but so far have seen no description of exactly what they did.

I would be tickled if my Unix tar program became an MSDOS standard but
it's not what I expect or hope for.  I wrote it for the GNU project,
the free Unix clone in source for everybody project.  If you can use it,
fine, if not, also fine.
-- 
{pyramid,ptsfa,amdahl,sun,ihnp4}!hoptoad!gnu			  gnu@toad.com
		"Watch me change my world..." -- Liquid Theatre