[NTLUG:Discuss] RAR

[cbbrowne@hex.net]

On Thu, 19 Apr 2001 19:15:39 CDT, the world broke into rejoicing as
nrut <baa204 at cronus.angelo.edu>  said:
> Chris Cox wrote:
> > I think the only RAR (an ugly thing IMHO) utility is
> > shareware for Linux.  Do a search for rar and linux
> > on a search engine.
> > 
> > And let me know what on earth makes rar a good format.
> 
> Back in my few BBS days I discovered this file format and found that the
> rar utility often compressed files better (by a considerable percentage)
> than the standard zip format in use back then.  I have no idea how it
> compares to gzip or bzip2 now.

Part of what likely happens is that RAR may compress the whole archive,
not just the contents.

Consider:  You'll often find that a .tgz file is considerably smaller
than the corresponding .zip file.  Case in point:  OpenQueue, in tgz form, 
is 152K in size, whilst the _same data_, in .zip form, consumes 183K.

The point of the exercise is that when you compress the _whole_ archive
at once, and not just the individual files in the archive, you can get
significantly better results.  For instance, TAR throws in a bunch of
header information...  That "bloats" the data, but it's _highly_ redundant,
compressing _real_ well.  In contrast, .zip files don't compress the header
info, and as they compress the component files independently, don't get
any benefit from inter-file-redundancy.  

bzip2 provides compellingly better compression than just about anything
else, so long as you can afford the CPU time.  It's worthwhile for
Linux kernel transfers, as it saves quite a lot of network bandwidth, but
for anything that's not getting transferred a bunch of time, it may not
be worthwhile...
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