[NTLUG:Discuss] What's this extension?

[cbbrowne@godel.brownes.org]

On Wed, 29 Sep 1999 20:11:14 CDT, the world broke into rejoicing as
Kyle Edbauer <abignerd at yahoo.com>  said:
> On Wed, 29 Sep 1999, Alex D. Coker wrote:
> 
> > I've got a tarball with an extension '.bz2'. What the heck is that, and
> > how do I de-compress it?
> 
> It is using bzip2.  You can pick up a copy at freshmeat.net.  The command
> to uncompress is bunzip2.  I've found that in most cases it compresses
> better than gzip.

"bzip2" is known as a "block sorting text compression" algorithm; it 
modifies Huffman encoding, and represents a "more compressing" algorithm
than the LZ77 algorithm that gzip uses.

This comes at the cost that bzip2 is more computationally expensive.
It is thus superior if a particular file must be transferred to many
people, and is quite large.  For instance, many people download the
Linux kernel (or updates thereof), which makes it worthwhile to use
bzip2 to eke out the bit of additional compression.

If, on the other hand, only one copy is to be transmitted, it is
reasonably likely that the hefty CPU load that results from compressing
the file will not prove worthwhile.

By the way, it is a good idea, when you are uncertain as to what
is in a file, to use the "file" command to ascertain what's in the
file.

For instance:

% file ~/Correspondence/NTLUG/*
/home/cbbrowne/Correspondence/NTLUG/Envelope.Chris.Cox: WordPerfect document
/home/cbbrowne/Correspondence/NTLUG/Envelope.Rick.Cook: WordPerfect document
/home/cbbrowne/Correspondence/NTLUG/JonPace:            WordPerfect document
/home/cbbrowne/Correspondence/NTLUG/LinuxCentral:       WordPerfect document
/home/cbbrowne/Correspondence/NTLUG/SigningOffsForm:    WordPerfect document
/home/cbbrowne/Correspondence/NTLUG/cover.Sept3:        WordPerfect document

% file ~/Correspondence/move/*
/home/cbbrowne/Correspondence/move/addresschange.aux: ASCII text
/home/cbbrowne/Correspondence/move/addresschange.dvi: TeX DVI file (TeX output 1998.11.29:1520‹)
/home/cbbrowne/Correspondence/move/addresschange.log: TeX transcript text
/home/cbbrowne/Correspondence/move/addresschange.ps:  PostScript document text conforming at level 2.0
/home/cbbrowne/Correspondence/move/addresschange.tex: ASCII text

This represents a vastly more accurate assessment of "file type" than 
looking at "file extensions" is likely to give you.

--
Rules of the Evil Overlord #42. "I will see to it that plucky young
lads/lasses in strange clothes and with the accent of an outlander
shall REGULARLY climb some monument in the main square of my capital
and denounce me, claim to know the secret of my power, rally the
masses to rebellion, etc. That way, the citizens will be jaded in case
the real thing ever comes along." 
<http://www.eviloverlord.com/lists/overlord.html>
cbbrowne at ntlug.org- <http://www.ntlug.org/~cbbrowne/lsf.html>