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@@ -0,0 +1,141 @@ +This is the file README for the gzip distribution. + +The GNU gzip home page is http://www.gnu.org/software/gzip. + +gzip (GNU zip) is a compression utility designed to be a replacement +for 'compress'. Its main advantages over compress are much better +compression and freedom from patented algorithms. The GNU Project +uses it as the standard compression program for its system. + +gzip currently uses by default the LZ77 algorithm used in zip 1.9 (the +portable pkzip compatible archiver). The gzip format was however +designed to accommodate several compression algorithms. See below +for a comparison of zip and gzip. + +gunzip can currently decompress files created by gzip, compress or +pack. The detection of the input format is automatic. For the +gzip format, gunzip checks a 32 bit CRC. For pack, gunzip checks the +uncompressed length. The 'compress' format was not designed to allow +consistency 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 that +the .Z file is correct simply because the standard uncompress does not +complain. This generally means that the standard uncompress does not +check its input, and happily generates garbage output. + +gzip produces files with a .gz extension. Previous versions of gzip +used the .z extension, which was already used by the 'pack' +Huffman encoder. gunzip is able to decompress .z files (packed +or gzip'ed). + +Several planned features are not yet supported (see the file TODO). +See the file NEWS for a summary of changes since the last release. +See the file INSTALL for installation instructions. + +WARNING: gzip is sensitive to compiler bugs, particularly when +optimizing. Use "make check" to check that gzip was compiled +correctly. Try compiling gzip without any optimization if you have a +problem. + +Please send all comments and bug reports by electronic mail to +<bug-gzip@gnu.org>. + +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 bug + +If you send me patches for machines I don't have access to, please test them +very carefully. gzip is used for backups, it must be extremely reliable. + +The znew and gzexe shell scripts provided with gzip benefit from +(but do not require) the (non-GNU) cpmod utility to transfer file attributes. + +The sample programs zread.c, sub.c and add.c in subdirectory sample +are provided as examples of useful complements to gzip. Read the +comments inside each source file. The perl script ztouch is also +provided as example (not installed by default since it relies on perl). + + +gzip is free software, you can redistribute it and/or modify it under +the terms of the GNU General Public License, a copy of which is +provided under the name COPYING. The latest version of gzip are always +available from ftp://ftp.gnu.org/gnu/gzip or in any of the gnu +mirror sites. + +- sources in gzip-*.tar (or .shar or .tar.gz). +- 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 was compiled with + djgpp 1.10 available in directory omnigate.clarkson.edu:/pub/msdos/djgpp. + +A VMS executable is in ftp://ftp.spc.edu/[.macro32.savesets]gzip-1-*.zip +(use [.macro32]unzip.exe to extract). A PRIMOS executable is available +in ftp://ftp.lysator.liu.se/pub/primos/run/gzip.run. + +Some ftp servers can automatically make a tar.Z from a tar file. If +you are getting gzip for the first time, you can ask for a tar.Z file +instead 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 gzip +are two really different programs, although the actual compression and +decompression sources were written by the same persons. A different +name 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 archive +file. 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 files +created by compress and pack. zip 1.9 and gzip do not support +compression methods other than deflation. (zip 1.0 supports shrink and +implode). Better compression methods may be added in future versions +of gzip. zip will always stick to absolute compatibility with pkzip, +it is thus constrained by PKWare, which is a commercial company. The +gzip header format is deliberately different from that of pkzip to +avoid such a constraint. + +On Unix, gzip is mostly useful in combination with tar. GNU tar +1.11.2 and later has a -z option to invoke gzip automatically. "tar -z" +compresses better than zip, since gzip can then take advantage of +redundancy between distinct files. The drawback is that you must +scan the whole tar.gz file in order to extract a single file near +the end; unzip can directly seek to the end of the zip file. There +is no overhead when you extract the whole archive anyway. +If a member of a .zip archive is damaged, other files can still +be recovered. If a .tar.gz file is damaged, files beyond the failure +point cannot be recovered. (Future versions of gzip will have +error recovery features.) + +gzip and gunzip are distributed as a single program. zip and unzip +are, for historical reasons, two separate programs, although the +authors of these two programs work closely together in the Info-ZIP +team. zip and unzip are not associated with the GNU project. +See http://info-zip.org/ for more about zip and unzip. + + +For any copyright year range specified as YYYY-ZZZZ in this package +note that the range specifies every single year in that closed interval. + +======================================================================== + +Copyright (C) 1999, 2001-2002, 2006-2007, 2009-2016 Free Software Foundation, +Inc. +Copyright (C) 1992, 1993 Jean-loup Gailly + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the ``GNU Free +Documentation License'' file as part of this distribution. |