"Armistead, Jason" <[email protected]> wrote: > Dustin wrote: > > >The entire original email was focused on ustar functionality, by my > >read. Perhaps you can repeat your experiment, bearing in mind that > >you're expecting a GNU Tar archive, and let us know what happens? > > My original experiment WAS with GNU formatted tar archives. Some work, and > some don't. I have far larger tar files that are working OK. But this one, > from a very important filesystem, is not. That is what led me to look more > closely at the bytes in the file header records.
GNU tar archives by default have vendor specific extension from a definition in POSIX.1-1988. As POSIX.1-1988 does not include a way to to associate extensions to a specific vendor, implementing POSIX.1-1988 extensions cause a risk of missinterpreting archive content. > With regard to my e-mail, I made a newbie blunder (having never looked under > the hood of tar before), and assumed that because the resulting files > contained "ustar" in the header, they must have been in Ustar format. > > If I'm correct it my understanding, a GNU formatted achive should also > contain "ustar" (followd by a null) at offset 257 and "00" at offset 263. Is > this correct for GNU format archives ? No, a GNU tar archive is not even compliant to POSIX.1-1988 as it does not implement long path names acording to POSIX.1-1988. GNU tar archives are identified by "ustar " and careful tar implementations only decode GNU tar vendor specific extensions if the archive can be identified as a GNU tar archive. > >Also, 7-zip claims to support "TAR" format, but doesn't say which > >format - are you sure it's designed to support GNU Tar archives? If > >you create a tar file with --format=ustar, can you read it with 7-zip? > > 7-Zip is decidedly vague on what sort of TAR it supports. I now have the > source code, but it still doesn't explain what TAR format(s) it supports. > Time permitting, I'll try to instrument it to figure out where it's breaking, > and to understand what format(s) it supports. 7-Zip's author didn't leave > many comments in his code, and doesn't have the ability to conditionally add > in debugging. It could take me some time. I recommend to use star, star supports 7z compression. Jörg -- EMail:[email protected] (home) Jörg Schilling D-13353 Berlin [email protected] (uni) [email protected] (work) Blog: http://schily.blogspot.com/ URL: http://cdrecord.berlios.de/private/ ftp://ftp.berlios.de/pub/schily
