Subject: Re: pax-as-tar and return codes (leading to pkg_info probs)
To: Hubert Feyrer <>
From: Christos Zoulas <>
List: tech-userlevel
Date: 08/05/2004 19:26:14
On Aug 5, 11:15pm, (Hubert Feyrer) wrote:
-- Subject: pax-as-tar and return codes (leading to pkg_info probs)

| Hi Christos,
| I'm writing you as the pax-as-tar maintainer with a wish for a change:
| Gavan pointed me at the fact that using pkg_info on a x11-links binary pkg
| (or any other meta-pkg) won't work, as it doesn't have all the files a
| "normal" package has:
| 	miyu% pkg_info /usr/pkgsrc/packages/i386/All/x11-links-0.23.tgz
| 	tar: WARNING! These patterns were not matched:
| 	pkg_info: extract of /usr/pkgsrc/packages/i386/All/x11-links-0.23.tgz 	failed
| 	pkg_info: error during unpacking, no info for 	'/usr/pkgsrc/packages/i386/All/x11-links-0.23.tgz' available
| Well, guess what, the problem is tar(1) returning different error codes on
| 1.6.2 (our hacked gtar) and 2.0 (pax-as-tar) when a filename is given to
| display (tar -t) or extract (tar -x) that is not contained in the archive,
| like +MTREE_DIRS.
| On 1.6.2, tar returns 0 in that situation, for both --fast-read present or
| not. On 2.0_BETA, tar returns 1 on that situation, again for presence and
| absence of --fast-read. This difference explains the failure, as pkg_info
| tails if a value != 0 is returned.
| I see two ways to fix this:
| a) move back to returning 0 in that case
| b) return some other error that makes it clear what failed in that case,
|    e.g. 2
| For comparison,
|  * Solaris' /usr/bin/tar returns 1 if it can't extract a file
|    and 2 if something else went wrong (while they don't document details
|    on the error cases!),
|  * GNU tar returns 2 in several cases, while I couldn't find documentation
|    of errors in either the manpage nor the info-page
|  * SUSv3 doesn't cover tar at all, and for pax it just says that a
|    non-zero exit status should be printed if a file can't be extracted
|    from an archive.
| As such, I'd say we should go for solution b) and document it properly, so
| that pkg_info can make use of it.
| It would be good if we could get those changes into 2.0 ...
| What do you think?

The portable way to fix this, is to invoke tar twice. Once to get the list
of files and a second to extract them. This way, you can use any version of
tar you like. I am not opposed to changing pax to exit with a different error
code if a file is not found, but I think it is better to be portable.