Best of the Newsgroups: zip vs. gzip, compress, pack

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Editor's note: I tried a Mac version of p7zip. It's a great archiver, but do we care? Disk space is so cheap now and high speed Internet is so common - I almost never care about compression.

From: Bela Lubkin <filbo@armory.com>
Subject: Re: cpio files to remote server
Date: 24 Sep 2005 17:39:02 -0400
Message-ID: <200509241438.aa19891@deepthought.armory.com> 
References: <1127247752.536290.93790@z14g2000cwz.googlegroups.com> <pohZe.2648$zQ3.1492@newsread1.news.pas.earthlink.net> 

sds10@earthlink.net wrote:

> I know this is slightly off topic but some answers later in this chain 
> mention gzip.
> 
> Any thoughts as to whether that more or less efficient than the old uniz zip 
> and unzip we have been using for years?

The algorithm used by `gzip` is one of the ones used by `zip`.  `zip`
supports several algorithms and tries to choose which one will produce
the smallest output (actually the Unix port of `zip` just uses one
algorithm, called "deflate").

`gzip` and `bzip2` are single-file compressors: foo -> foo.gz or
foo.bz2.  `zip` and many others like it are combined archivers and
compressors.  Running `zip foo.zip foo bar baz` creates a single file,
foo.zip, that contains those three files.  The equivalent with `gzip`
would be something like: `tar cf foo.tar foo bar baz; gzip foo.tar`.

`zip` archive format is imperfect for Unix purposes: it doesn't store
all Unix attributes, I don't think it stores directory permissions,
stuff like that.  As long as you keep those things in mind it's probably
fine.

> I prefer the unix zip and unzip programs because they are completely 
> compatible with the zip and unzip programs built into Windows XP and also 
> with older zip programs.

There are so many newer archivers for Windows -- `zip` is rather
archaic.  Two of the most popular ones these days are `rar` and `7-zip`.
I've been experimenting with these and have found that `7-zip` can get
the best compression of any compressor I've ever tried.  Note that I say
"_can_" get.  It has a lot of knobs you can twiddle.  Its default
compression is similar to that of `rar`.  (I'm working on some long-term
archival storage where minimizing size is more important than saving
compression time.  For typical backup tasks, a faster compressor that
leaves a few percent on the table is probably more appropriate.)

7-zip for Unix lives at http://p7zip.sourceforge.net/.  I'm not aware of
an OpenServer port (I've been fiddling with it on Windows & Linux).

> I know for sure that compress and pack (in Unix) are, in most instances, 
> less efficient than zip and unzip for un-compiled programs and data files. 
> They may all turn out to be equally efficient for binary files, however.

`pack` is an ancient algorithm that is always less efficient that the
modern ones.  `compress` is newer and more efficient, but still nowhere
near the more modern compressors.

>Bela<
 

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