Re: [Bug-tar] Re: Is there any documentation for '-H pax'?

[Joerg Schilling]

Sergey Poznyakoff <address@hidden> wrote:

> Fan Decheng <address@hidden> wrote:
>
> > I read the info document came with tar-1.15.1, but I
> > didin't find any documentation on -H, and I found
> > something on pax but don't know what they really mean.
>
> See --format=posix in chapter 'tar Options' (online version
> at http://www.gnu.org/software/tar/manual/html_node/tar_43.html#SEC43),
> and the discussion of various tar formats in chapter 'Controlling the
> Archive Format' (online version at
> http://www.gnu.org/software/tar/manual/html_node/tar_120.html#SEC120).

Let me try to comment some bugs in the man page:

http://www.gnu.org/software/tar/manual/html_node/tar_136.html#SEC136

I am sure then GNU cpio is not able to handle file names of arbitrary size.

In POSIX mode the maximum is 262143 chars and I am sure that GNU cpio
will probably list these files but is unable to extract them from the archive
to the disk.


http://www.gnu.org/software/tar/manual/html_node/tar_120.html#SEC120

gnu:

The GNU tar archive format is not derived from an early POSIX standard,
it is incompatbible with even the oldest version of POSIX.1-1988.
It is even incompatile to the April 1986 draft for POSIX.1-1988.
SUG-tar/PD-tar that GNU tar was derived from in 1989 implemented a true
and compatible subset of POSIX.1-1988. The incompatibilities to POSIX.1-1988
have been introduced in 1989 - one year afher the final POSIX.1-1988 came out.

I first send a bug report to this documentation problem in 1994, could 
you please be so kind and correct it now?


oldgnu:

Could you please document the differences between "gnu" & "oldgnu"?


v7:

The v7 tar archive format does not support directories. I would guess that
you need to correct the man page & the code as well.

The V7 tar archives format does not support symbolic links.
The only file types supported are plain files and hard links.

Conclusion: It seems that you did rather implement the BSD-4.2 tar 
archive format that I call "tar" in star.

Could you do a rename and either add a real v7 format or document
in the man page that GNU tar does not support v7 tar?


ustar:

seems to be OK and my "tartest" program now even passes the related 
implementation from GNU tar-1.15.1 - congratulations!


star:

I am sure that GNU tar does not support the 'star' format.
The 'star' archive format is a "clean extension" to the "BSD-4.2 tar"
archive format (which is what most people call "tar" format).

The 'star' archive format is from 1985 (long before GNU tar or 
even POSIX.1-1988 drafts have been around). It is not POSIX.1-1988
compliant.

I asume that GNU tar rather implements read support for the "xstar" & "xustar"
archive format, so please correct your man page.


posix:

This is a really bas idea for an archive format name as the POSIX.1-1988
tar archive format is called "ustar" and the POSIX.1-2001 tar archive format
is called "pax" - none of both is called "posix" and using "posix" is a source
for consufuion. 

Please try to correct this.


The table that follows is not correct too:

Unless the GNU tar program implements more than I did
negotiate with Paul Eggert, a base 256 number (GNU tar 8 byte 
fields) can hold 56 bits and a a base 256 number (12 byte fields)
can hold 88 bits. The numbers in the table seem to be wrong.....

Pre-POSIX.1-1988 tar implementations cannot support more than
a filesize of 2147483646 bytes. 

Only tar implelemtations made after 1995 (the large file summit)
support files up to 8589934591 bytes.

GNU tar definitely is not able to handle filenames of arbitrary size.
GNU tar seems to be limited  to 1024 chars (I did just test this with 1.15.1).

The POSIX PATH name length is not unlimited but limited to 8589934574
bytes in case _no_ other POSIX.1-2001 extended header field is used.

So most entries in the table would need to be corrected.....

Jörg

-- 
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