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Date:      Mon, 10 Mar 2008 00:19:33 +0100
From:      "Danny Pansters" <danny@ricin.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: tar( bzip2 parts of manpage )
Message-ID:  <200803100019.33200.danny@ricin.com>
In-Reply-To: <47D46A4B.6050409@mkdev.eu>
References:  <47D46A4B.6050409@mkdev.eu>

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On Sunday 09 March 2008 23:52:59 Markus Klaschka wrote:
> Hi,
> I never used built-in bzip functionality of tar, but I like bzip2 more
> than gzip, so I just searched and found following:
>      -j      (c mode only) Compress the resulting archive with bzip2(1). 
> In extract or list modes, this option is ignored.  Note that, unlike
>              other tar implementations, this implementation recognizes
> bzip2 compression automatically when reading archives.
> and
>      -y      (c mode only) Compress the resulting archive with bzip2(1). 
> In extract or list modes, this option is ignored.  Note that, unlike
>              other tar implementations, this implementation recognizes
> bzip2 compression automatically when reading archives.
>
> what's going on there?
>
> I tested the -j option, works good. I created a file.tar.bz2 and like
> the manpage describes, tar -cvf is enough to unpack the tarball,

you mean tar xvf

> Is that a FreeBSD feature, how is it on other platforms?
> Is bzip2 used, or is that build in as a tar?

bsdtar != gtar

In bsdtar -j (-y) indeed uses bzip2 to compress rather than gzip and upon 
unpacking it handles both tgz and tbz transparantly that's why you don't need 
to specify -j there (different from gtar IIRC). I think -j and -y are mainly 
there to be compatible with gtar but I'm not sure. Note that both bsdtar and 
bzip2 are in base and have been for a while so it seems like a logical 
feature for bsdtar. Knowing whether its a gzip or bzip2 compressed is easy to 
see from magic numbers.

Cheers,

Dan 

>
> Cheers
>
> -
> Markus Klaschka
> MKDev - Markus Klaschka Development
> http://www.mkdev.eu
>
> Spain: 	0034 - 63 747 23 07
> UK:
> 	0044 - 750 910 2718
> Mail: 	mk@mkdev.eu <mailto:mk@mkdev.eu>
> Skype: 	mark-use
> IRC: 	mark-use @ irc.freenode.net : #freebsd, ##security, #freebsd-src,
> #bsdforen.de, #bsdgroup.de





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