This is the file README for the gzip distribution, version 1.2.4.gzip (GNU zip) is a compression utility designed to be a replacementfor 'compress'. Its main advantages over compress are much bettercompression and freedom from patented algorithms.  The GNU Projectuses it as the standard compression program for its system.gzip currently uses by default the LZ77 algorithm used in zip 1.9 (theportable pkzip compatible archiver). The gzip format was howeverdesigned to accommodate several compression algorithms. See belowfor a comparison of zip and gzip.gunzip can currently decompress files created by gzip, compress orpack. The detection of the input format is automatic.  For thegzip format, gunzip checks a 32 bit CRC. For pack, gunzip checks theuncompressed length.  The 'compress' format was not designed to allowconsistency checks. However gunzip is sometimes able to detect a bad.Z file because there is some redundancy in the .Z compression format.If you get an error when uncompressing a .Z file, do not assume thatthe .Z file is correct simply because the standard uncompress does notcomplain.  This generally means that the standard uncompress does notcheck its input, and happily generates garbage output.gzip produces files with a .gz extension. Previous versions of gzipused the .z extension, which was already used by the 'pack'Huffman encoder. gunzip is able to decompress .z files (packedor gzip'ed).Several planned features are not yet supported (see the file TODO).See the file NEWS for a summary of changes since 0.5.  See the fileINSTALL for installation instructions. Some answers to frequentlyasked questions are given in the file INSTALL, please read it. (Inparticular, please don't ask me once more for an /etc/magic entry.)WARNING: on several systems, compiler bugs cause gzip to fail, inparticular when optimization options are on.  See the section "Specialtargets" at the end of the INSTALL file for a list of known problems.For all machines, use "make check" to check that gzip was compiledcorrectly.  Try compiling gzip without any optimization if you have aproblem.Please send all comments and bug reports by electronic mail to:   Jean-loup Gailly <jloup@chorus.fr>or, if this fails, to bug-gnu-utils@prep.ai.mit.edu.Bug reports should ideally include:    * The complete output of "gzip -V" (or the contents of revision.h      if you can't get gzip to compile)    * The hardware and operating system (try "uname -a")    * The compiler used to compile (if it is gcc, use "gcc -v")    * A description of the bug behavior    * The input to gzip, that triggered the bugIf you send me patches for machines I don't have access to, please test themvery carefully. gzip is used for backups, it must be extremely reliable.The package crypt++.el is highly recommended to manipulate gzip'edfile from emacs. It recognizes automatically encrypted and compressedfiles when they are first visited or written. It is available viaanonymous ftp to roebling.poly.edu [128.238.5.31] in /pub/crypt++.el.The same directory contains also patches to dired, ange-ftp and info.GNU tar 1.11.2 has a -z option to invoke directly gzip, so you don't have topatch it. The package ftp.uu.net:/languages/emacs-lisp/misc/jka-compr19.el.Zalso supports gzip'ed files.The znew and gzexe shell scripts provided with gzip benefit from(but do not require) the cpmod utility to transfer file attributes.It is available by anonymous ftp on gatekeeper.dec.com in/.0/usenet/comp.sources.unix/volume11/cpmod.Z.The sample programs zread.c, sub.c and add.c in subdirectory sampleare provided as examples of useful complements to gzip. Read thecomments inside each source file.  The perl script ztouch is alsoprovided as example (not installed by default since it relies on perl).gzip is free software, you can redistribute it and/or modify it underthe terms of the GNU General Public License, a copy of which isprovided under the name COPYING. The latest version of gzip are alwaysavailable by ftp in prep.ai.mit.edu:/pub/gnu, or in any of the prepmirror sites:- sources in gzip-*.tar (or .shar or .tar.gz).- Solaris 2 executables in sparc-sun-solaris2/gzip-binaries-*.tar- MSDOS lha self-extracting exe in gzip-msdos-*.exe. Once extracted,  copy gzip.exe to gunzip.exe and zcat.exe, or use "gzip -d" to decompress.  gzip386.exe runs much faster but only on 386 and above; it is compiled with  djgpp 1.10 available in directory omnigate.clarkson.edu:/pub/msdos/djgpp.A VMS executable is available in ftp.spc.edu:[.macro32.savesets]gzip-1-*.zip(use [.macro32]unzip.exe to extract). A PRIMOS executable is availablein ftp.lysator.liu.se:/pub/primos/run/gzip.run.OS/2 executables (16 and 32 bits versions) are available inftp.tu-muenchen.de:/pub/comp/os/os2/archiver/gz*-[16,32].zipSome ftp servers can automatically make a tar.Z from a tar file. Ifyou are getting gzip for the first time, you can ask for a tar.Z fileinstead of the much larger tar file.Many thanks to those who provided me with bug reports and feedback.See the files THANKS and ChangeLog for more details.		Note about zip vs. gzip:The name 'gzip' was a very unfortunate choice, because zip and gzipare two really different programs, although the actual compression anddecompression sources were written by the same persons. A differentname should have been used for gzip, but it is too late to change now.zip is an archiver: it compresses several files into a single archivefile. gzip is a simple compressor: each file is compressed separately.Both share the same compression and decompression code for the'deflate' method.  unzip can also decompress old zip archives(implode, shrink and reduce methods). gunzip can also decompress filescreated by compress and pack. zip 1.9 and gzip do not supportcompression methods other than deflation. (zip 1.0 supports shrink andimplode). Better compression methods may be added in future versionsof gzip. zip will always stick to absolute compatibility with pkzip,it is thus constrained by PKWare, which is a commercial company.  Thegzip header format is deliberately different from that of pkzip toavoid such a constraint.On Unix, gzip is mostly useful in combination with tar. GNU tar1.11.2 has a -z option to invoke gzip automatically.  "tar -z"compresses better than zip, since gzip can then take advantage ofredundancy between distinct files. The drawback is that you mustscan the whole tar.gz file in order to extract a single file nearthe end; unzip can directly seek to the end of the zip file. Thereis no overhead when you extract the whole archive anyway.If a member of a .zip archive is damaged, other files can stillbe recovered. If a .tar.gz file is damaged, files beyond the failurepoint cannot be recovered. (Future versions of gzip will haveerror recovery features.)gzip and gunzip are distributed as a single program. zip and unzipare, for historical reasons, two separate programs, although theauthors of these two programs work closely together in the info-zipteam. zip and unzip are not associated with the GNU project.The sources are available by ftp in	 oak.oakland.edu:/pub/misc/unix/zip19p1.zip	 oak.oakland.edu:/pub/misc/unix/unz50p1.tar-z