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1.1 root 1: This is the file README for the gzip distribution, version 1.0.5.
2:
3: gzip (GNU zip) is a compression utility designed to be a replacement
4: for 'compress'. Its main advantages over compress are much better
5: compression and freedom from patented algorithms. The GNU Project
6: uses it as the standard compression program for its system.
7:
8: gzip currently uses by default the LZ77 algorithm used in zip 1.9 (the
9: portable pkzip compatible archiver). The gzip format was however
10: designed to accommodate several compression algorithms.
11:
12: gunzip can currently decompress files created by gzip, zip (with
13: restrictions), compress or pack. (The SCO 'compress -H' format will be
14: supported in a future version.) The detection of the input format is
15: automatic. When using the first two formats, gunzip checks a 32 bit
16: CRC. For pack, gunzip checks the uncompressed length. The 'compress'
17: format was not designed to allow consistency checks. However gunzip is
18: sometimes able to detect a bad .Z file because there is some
19: redundancy in the .Z compression format. If you get an error when
20: uncompressing a .Z file, do not assume that the .Z file is correct
21: simply because the standard uncompress does not complain. This
22: generally means that the standard uncompress does not check its input,
23: and happily generates garbage output.
24:
25: gzip produces files with a .z extension. This was chosen to mimic the
26: 'compress' .Z extension. Using exactly the same extension would have
27: caused too much confusion. Using a completely different extension
28: would have forced changes in other programs such as GNU tar (which has
29: a -z option). The .z extension is already used by the 'pack'
30: Huffman encoder, but gunzip is able to decompress packed files.
31:
32: Several planned features are not yet supported (see the file TODO).
33: See the file INSTALL for installation instructions. See the file NEWS
34: for a summary of changes since 0.5.
35:
36: WARNINGS about broken optimizers:
37:
38: - on the NeXT, "cc -finline-functions" is broken. gzip produces
39: valid .z files but they are much too large because the string
40: matching code misses most matches. Use "cc -O" instead.
41:
42: - on the Mips R4000, gcc -O (version 2.3.1) generates bad code, use cc
43: or just gcc -g instead.
44:
45: - on SparcStation with SunOS 4.1.1 and the SC1.0 compiler, the optimizer
46: works up to -O3 but -O4 does not work.
47:
48: - MSC 5.1 with -Ox and -DDYN_ALLOC generates bad code in inflate.c.
49: The default is static allocation (no DYN_ALLOC) and -Ox works on inflate.c.
50: But -Ox does not work on util.c, so you must use -Oait -Gs.
51:
52: For all machines, Use "make check" to check that gzip was compiled correctly.
53:
54: Please send all comments and bug reports by electronic mail to:
55: Jean-loup Gailly <[email protected]>
56:
57: or, if this fails, to [email protected].
58: Bug reports should ideally include:
59:
60: * The complete output of "gzip -V" (or the contents of revision.h
61: if you can't get gzip to compile)
62: * The hardware and operating system
63: * The compiler used to compile
64: * A description of the bug behavior
65: * The input to gzip, that triggered the bug
66:
67: The package crypt++.el is highly recommended to manipulate gzip'ed
68: file from emacs. It recognizes automatically encrypted and compressed
69: files when they are first visited or written. It is available via
70: anonymous ftp to roebling.poly.edu [128.238.5.31] in /pub/crypt++.el.
71: The same directory contains also patches to dired, ange-ftp, info and
72: tar. A patch for tar 1.11.1 is included in the gzip distribution
73: because too many people independently reinvent it (see gzip-tar.patch).
74:
75: gzip is free software, you can redistribute it and/or modify it under
76: the terms of the GNU General Public License, a copy of which is
77: provided under the name COPYING. The latest version of the gzip
78: sources can always be found in prep.ai.mit.edu:/pub/gnu/gzip-*.tar*
79: or any of the prep mirror sites. An MSDOS lha self-extracting exe is in
80: hal.gnu.ai.mit.edu:/tmp/gzip*.exe.
81:
82: Many thanks to those who provided me with bug reports and feedback.
83: See the files THANKS and ChangeLog for more details.
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