question about TAR

[Owen Townend]

On Thu, 2007-11-29 at 23:14 +0100, Ouattara Oumar Aziz (alias wattazoum)
wrote:
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> Hello
> 
> I would like to know if it's possible to transfer a file from one tar
> archive to another (without untarring it on the disk)
> 
> For example , I have a 2GB dir in a TAR archive and I want to transfer a
> subdir of 1GB to another TAR file. I don't have 1GB free on my disk .
> Can Tar handle this ?
> 
> Best regards
> wattazoum
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> 

Hey,
  Tar can add to an existing archive (--append or --concatenate), so the
second part's OK. Tar can extract parts of and archive (--extract) and
tar can remove parts of an archive (--delete) but I am not sure there is
a way to use all of these simultaneously to facilitate a move. Some disk
space will need to be used.
  Depending on the file sizes you may be able to use the available space
and do the move in many small steps instead of one large one. Another
option could be to extract the files to an external storage medium,
remove them from the previous archive before then re-reading them into
the new archive.
  Do you have other IO available if there's no disk space? A spare tape
or networked machine?

  Just some thoughts.

cheers,
Owen.