Re: Use tar to append?

Mike McCarty wrote:

I have a backup script which I run on some sort of regular
basis. I use tar to create an archive, which I then split
into pieces of CDROM size (703MB) and write to CDROMs.

Originally, I wrote it such that it added directories one
by one to the archive, but found that it took inordinately
long periods of time. A little investigation showed that
each time it started up tar, the entire archive got copied,
another directory got added, and then the archive was renamed.

Since there are about 15 directories that I back up, that
meant *lots* of copying.

So, now I just put them all in there at once. But I'm missing
the progress indicators I used to get. For example, during
the "verification phase" I used to have...

for path in $backupdirs
do
    echo "Verifying $path...." | wall
    tar tzf /tmp/backup.tar.gz 1>/dev/null && \
        echo "$path: verified" | wall || \
        echo "$path: errors in verify" | wall
    if [ $? -eq 0 ]
        then echo "$path: verified"
        else echo "$path: error(s) in verify" 1>&2
    fi
done

Is there a way to get tar to use the archive it is adding to
"in place"? I've read man and info, and I see --append
(which is what I was using) and --catenate (which looks
marginally faster, perhaps, since I compress), but see
no way to make it "just do it" without doing an implicit
copy.

--
  Les Mikesell
    lesmikesell@xxxxxxxxx