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From: hst@mh_co2.mh.nl (Klaas Hemstra)
Newsgroups: comp.compression
Subject: Compressing more then one file in one compression-run ?
Message-ID: <5655@mhres.mh.nl>
Date: 16 May 91 16:49:07 GMT
Sender: news@mhres.mh.nl
Lines: 49

I have an idea for all of you archive-builders.
It would be nice if the archivers would be able to compress multiple files
in one compression-run. This way it would be possible to obtain much higher
compression ratio's for certain sets of files.
For example: If you have a lot of C sources in one directory and you want
to compress it using PKZIP or ARC or ZOO, each file is compressed seperately.
If you make a tar archive (with unix tar) and then compress it with unix
compress, the compression ratio will be better.

I recently obtained the new ARJ archiver. It has an option which lets you
store a file to an archive (.ARJ file) without compressing it. By first
using this option on all the files and then compression the resulting ARJ
archive, the compression ratio improved drastically on those archives which
contain a lot of simular or small files.

So I would like to suggest an option with the meaning:
- Compress all file with the same extention in one run.
(or some other simular conditions like small files, C+H files etc.)

Of course it will be more difficult to extract a single file from that archive
(the preceding files have to decompressed too), but that's a minor technical
problem.
I use PKZIP and ARJ mostly to backup programs i.e. directory trees.
Therefore I seldomly extrace only one file from an archive.

Example:
Suppose you want to make an archive containing the following files:
	AAA.EXE BBB.C  DDD.EXE EEEE.C FFF.EXE GGGG.C
This would be compressed on a per file bases with most current archive
programs.
I would like the files to be compressed like this:
	BBB.C   	\
	EEEE.C		 \
	GGGG.C		  \   One compression (LZW ?) run
	AAA.EXE		\
	DDD.EXE		 \
	FFF.EXE		  \   Another compression (LZW ?) run


If I missed some extention to an archiver that could do this please excuse me
(I don't like reading manuals anyway).

Any comments ?
								Klaas

Klaas Hemstra  (hst@mh.nl)                      |   /  / ,~~~ ~~/~~
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