On Fri, 2009-08-07 at 13:14 +0200, Christian Maeder wrote:
Christian Maeder wrote:
Matthias Kilian wrote:
However, to create an archive, you can use something like
$ pax -wf foo.tar directory
Do you think "gtar --format=posix" would be different from pax?
I would expect they are the same. The USTAR format is standardised by a POSIX standard from 1988 while the pax extensions are standardised by POSIX from 2001 I think. The pax program has an -x format flag and can use pax, ustar or cpio formats. The pax format is an extension of the ustar format.
The only question is, if we should create archives using the ustar, posix/pax, or gnu format. ustar seems to be the least common denominator. Does ustar have any disadvantages?
For source code distribution I think the ustar format is ideal. This is what cabal-install's sdist mode uses. As you say it's the lowest common denominator. The limitations of the format (file sizes, lack of extended file meta-data) are not a practical problem for source code or binaries.
My plain tar command under solaris cannot handle the pax files, too. So ustar archives should be created (at least under solaris).
That's odd since pax is supposed to be a compatible extension of ustar that just adds extra meta-data entries. Older programs should either ignore those entries or extract them as if they were ordinary files.
But I don't know why the ustar format can handle long file names,
The ustar format can handle file names up to 100+155 characters (bytes) long. The reason for 100+155 is that it's not simply 255. The split into a 100 and 155 field must happen on a directory separator.
whereas the gnu format creates a "@LongLink" file and pax a "PaxHeader" file (when unpacked with tar).
Right, those "files" are the extended entries. Duncan