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

[Alexander T]

Hi again,

Just as a side note, this was apparently already added to info-zip in
version 3.0 (flag -FI).

Regards,

Alex

On 1/8/10, Alexander T <address@hidden> wrote:
> 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
>>>
>>>
>>>
>>>
>>
>