What you're talking about would require the ability to address a
compressed tar the way you do a filesystem, with the ability to seek,
insert, delete, overwrite.
disk|partition|filesystem|file|compression|tar|foo
the nature of stream compression doesn't allow insertions.
you'd have to blow up the tar out of the compression to modify it, and
even the -u option to some tars, whereby a contained file can be modified,
involves streaming the tar from the original copy through the changed
file, inserting the changed file, and streaming the rest of the tar after
that file, all into a new file, which then replaces the original, much the
way gzip, compress, lzop, and others do when you apply them to a file.
Most advanced operating systems (and some not-so-advanced (dos, windoze))
support transparent compression somewhere below the file APIs.
There was doublefs for linux way back, whereby you mounted a file or
partition on a sort of a loopback device, and then could treat it as a
partition, with the kernel handling compression in/out of it. I'm sure
there's something like it still around, though disk space is so cheap now
that it's probably not generating much interest any more. It sure helped
me back in 1993, though.
AIX does compressed jfs filesystems, whereby the files themselves live on
the disk compressed, but the directory reports the uncompressed attributes
of the file, and it's uncompressed into the vfs manager for access.
Dos had stacker. Then, when Microsoft found out that people were paying
for it, they came out with their own version included in the OS.
Now, with Windows 2000 (fairly decent environment, actually... i'm using
it right now), and maybe earlier NT, you can apply the compressed
attribute to any object on the filesystem, and it treats files sort of in
the AIX model. If you set your destination directory as compressed and
with inheritance of the compression, the files will take up a lot less
space. For instance, I keep the doc from activeperl on my hard drive
(though i use the perl in cygwin), and i keep it in a compressed
directory. It's 7.85Mb, size on disk 4.28.
I hope you don't mind the cc to the rest of the list. it saves someone
else from wasting his time telling you the same thing.
"
If I have a file named 'foo' on the work system and a file named
'bar.tar.gz' on my home system that contains 'foo', the only way
I could
update 'bar.tar.gz' would be to simply create a new
'bar.tar.gz'? I was
hoping there would be a simpler way than this. The rsync backup size
right now is near 3 Gigs.
"
Tim Conway
tim.conway@philips.com
303.682.4917
Philips Semiconductor - Longmont TC
1880 Industrial Circle, Suite D
Longmont, CO 80501
Available via SameTime Connect within Philips, n9hmg on AIM
perl -e 'print pack(nnnnnnnnnnnn,
19061,29556,8289,28271,29800,25970,8304,25970,27680,26721,25451,25970),
".\n" '
"There are some who call me.... Tim?"