Use tar to append?

[Mike McCarty]

Cameron Simpson wrote:
> On 09Mar2007 10:17, Mike McCarty <Mike.McCarty at sbcglobal.net> wrote:

[snip]

> | >Regarding progress reporting, "tar cvf" reports nicely but interleaves any
> | >error message with the TOC, which is annoying and also hides the errors. I
> | I don't want to watch the xterm it's running in. I want a wall.
> 
> Easily done. Read each line from the TOC, and hand the interesting few
> to wall.

Ok.

> 
> | >have a suggestion for this, which is a little tacky but may work quite
> | >nicely:
> | >
> | >  >tarfile
> | 
> | This line looks like a syntax error to me. What is it
> | supposed to accomplish?
> 
> It is not a syntax error. It truncates the tarfile, ensuring it exists before
> the tail starts. It is otherwise possible for the tail to commence before the
> tar creates the file. Unlikely, but possible.

Ok. Thanks.

[snip]

> | Umm, two points. (1) Having one process writing and another reading
> | the same archive results in a "chase", eating lots of resources
> | while the reader tries to catch up with the writer.
> 
> Yes. Like I said, it's a little tacky.
> Measured the load? How nasty is it?

Haven't done that. Dunno how that would be done, actually,
except by measuring elapsed times to completion. The system
is completely used when tar is running. It would be an
interesting measurement, though.

> | (2) I don't
> | want a detailed report, I want a progress report so I can know
> | approx. how much has been done.
> 
> Which is why I suggested you do something other than "cat", like "grep".
> You post process the tvf output as you see fit.

Ok. Makes sense. I'll need to learn a little more shell syntax
to do that.

[snip]

> The other way, which is a little harder, is to run a "tar cvf" and post
> process its output as it goes. Have a look at "entar", a script of mine which
> does exactly that:
> 
>   http://www.cskk.ezoshosting.com/cs/css/bin/entar

Thanks, I'll have a look.

Mike
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