Re: [Bug-tar] Add option to include the contents of FIFO:s

[Alexander T]

Hi Tim,

Thank you for the information. I have submitted the same feature
request to info-zip to see if they could implement it. Considering
that the problem with the header appearing first would mostly apply to
sequential output, would it be possible to add support for this when
tar is writing the output file itself? Or maybe there is some other
chunking option which would limit the buffer size?

Regards,

Alex

On 1/7/10, Tim Kientzle <address@hidden> wrote:
> The tar format has to know the size of the entry
> before it can write the header that goes before
> the data.
>
> With your proposal, there's no way for tar to
> know the size of the data without actually
> reading all of the data.  To work around this,
> tar would have to copy the data to a temporary
> file itself.  So you wouldn't really gain
> anything over using a temporary file.
>
> In some cases, you might have a programmatic
> way to determine the size in advance.  If this
> is true for your application, you might consider
> writing a custom archiving program based on
> the libarchive library, which was designed to
> make it very easy to create tar archives with
> dynamically-generated content.  (If you cannot
> determine the size in advance, libarchive now
> has support for writing zip format, which does
> not require knowing the size in advance.)
>
> http://libarchive.googlecode.com/ has full
> details, including example code.
>
> Cheers,
>
> Tim Kientzle
>
> Alexander T wrote:
>> Hi,
>>
>> This is my first message to this list, so hi everyone and I hope that
>> this is the right place to post. I would like to submit a feature
>> request: to add a flag for including the contents of FIFO:s, like
>> --dereference, but for named pipes.
>>
>> The problem this would solve is tar:ing multiple large program outputs
>> without using intermediate files, something like
>>
>> mkdir bck
>> mkfifo bck/1.dump
>> mkfifo bck/2.dump
>> dbdump db1 > bck/1.dump &
>> dbdump db2 > bck/2.dump &
>> tar -c?f bck.tar bck
>>
>> It is currently of course possible to come up with some workarounds,
>> but they have drawbacks and this would IMHO be a very nice addition.
>>
>> There are some google results with people having the same problems:
>> http://www.unix.com/unix-advanced-expert-users/30365-tar-fifos.html
>> ,
>> http://stackoverflow.com/questions/2021873/linux-adding-named-files-to-a-zip-archive-from-a-pipe/2022012#2022012
>> and
>> http://www.linuxquestions.org/questions/programming-9/make-tarziprar-play-nice-with-named-pipes-593392/
>>
>>
>> Best Regards,
>>
>> Alexander T
>>
>>
>>
>>
>