Re: [Bug-tar] Modifying Volume Label with tar.

[Ralph Corderoy]

Hi Helmut,

> Ralph Corderoy <address@hidden> writes:
> > tar -V something -cf bar.tar dummyfile
> >
> > And is there any way to create a tar file with nothing but the
> > volume label, i.e. remove the need for dummyfile above?
> 
> You could give
> 
> $ tar -V something -cf bar.tar --files-from=/dev/null
> 
> a try.

Thanks, that works but shows up another inconsistency.

    $ tar -V foo -cf - | tar tvf -
    tar: Cowardly refusing to create an empty archive
    Try `tar --help' for more information.
    $ tar -V foo -cf - --files-from /dev/null | tar tvf -
    V--------- 0/0               0 2005-05-25 10:27:24 foo--Volume Header--
    $ tar -cf - --files-from /dev/null | tar tvf -
    $ tar -cf - --files-from /dev/null | wc -c    
      10240
    $ tar -cf - --files-from /dev/null | od -c
    0000000  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
    *
    0024000
    $ 

If there's no files specified in argv[] then tar's a coward.  But if
--files/from /dev/null is used then tar's happy to create an empty
archive.

I guess it's trying to avoid the `tar cf important_file' user error
where the tar filename has been omitted, but it makes creating an empty
archive, or an archive with just a volume label, harder in a portable
way, i.e. having to know the name of /dev/null on this platform.

Perhaps tar doesn't need to be a coward where the tar filename has been
specified as stdout?

    tar -cf -    # OK, won't trample anything.
    tar -cf foo  # Don't create empty archive in case of user error.

Although personally, I think it shouldn't be a coward at all since most
users learn through

    tar cf *.c *.h

and tar's cowardlyness doesn't help them.

Cheers,


Ralph.