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1.1     ! root        1: \input texinfo @c -*-texinfo-*-
        !             2: @c %**start of header
        !             3: @setfilename gzip.info
        !             4: @settitle Gzip User's Manual
        !             5: @finalout
        !             6: @setchapternewpage odd
        !             7: @c %**end of header
        !             8: 
        !             9: @ifinfo
        !            10: This file documents the the GNU @code{gzip} command for compressing files.
        !            11: 
        !            12: Copyright (C) 1992-1993 Jean-loup Gailly
        !            13: 
        !            14: Permission is granted to make and distribute verbatim copies of
        !            15: this manual provided the copyright notice and this permission notice
        !            16: are preserved on all copies.
        !            17: 
        !            18: @ignore
        !            19: Permission is granted to process this file through TeX and print the
        !            20: results, provided the printed document carries copying permission
        !            21: notice identical to this one except for the removal of this paragraph
        !            22: (this paragraph not being relevant to the printed manual).
        !            23: 
        !            24: @end ignore
        !            25: Permission is granted to copy and distribute modified versions of this
        !            26: manual under the conditions for verbatim copying, provided that the entire
        !            27: resulting derived work is distributed under the terms of a permission
        !            28: notice identical to this one.
        !            29: 
        !            30: Permission is granted to copy and distribute translations of this manual
        !            31: into another language, under the above conditions for modified versions,
        !            32: except that this permission notice may be stated in a translation approved
        !            33: by the Foundation.
        !            34: @end ifinfo
        !            35: 
        !            36: @titlepage
        !            37: @title gzip
        !            38: @subtitle The data compression program
        !            39: @subtitle Edition 1.0.5, for Gzip Version 1.0.5
        !            40: @subtitle March 1993
        !            41: @author by Jean-loup Gailly
        !            42: 
        !            43: @page
        !            44: @vskip 0pt plus 1filll
        !            45: Copyright @copyright{} 1992-1993 Jean-loup Gailly
        !            46: 
        !            47: Permission is granted to make and distribute verbatim copies of
        !            48: this manual provided the copyright notice and this permission notice
        !            49: are preserved on all copies.
        !            50: 
        !            51: Permission is granted to copy and distribute modified versions of this
        !            52: manual under the conditions for verbatim copying, provided that the entire
        !            53: resulting derived work is distributed under the terms of a permission
        !            54: notice identical to this one.
        !            55: 
        !            56: Permission is granted to copy and distribute translations of this manual
        !            57: into another language, under the above conditions for modified versions,
        !            58: except that this permission notice may be stated in a translation approved
        !            59: by the Foundation.
        !            60: @end titlepage
        !            61: 
        !            62: @node Top, , , (dir)
        !            63: 
        !            64: @ifinfo
        !            65: This file documents the @code{gzip} command to compress files.
        !            66: @end ifinfo
        !            67: 
        !            68: @menu
        !            69: * Copying::            How you can copy and share @code{gzip}.
        !            70: * Overview::           Preliminary information.
        !            71: * Sample::             Sample output from @code{gzip}.
        !            72: * Invoking gzip::      How to run @code{gzip}.
        !            73: * Advanced usage::     Concatenated files.
        !            74: * Environment::                The @code{GZIP} environment variable
        !            75: * Problems::           Reporting bugs.
        !            76: * Concept Index::      Index of concepts.
        !            77: @end menu
        !            78: 
        !            79: @node Copying, Overview, , Top
        !            80: @include gpl.texinfo
        !            81: 
        !            82: @node Overview, Sample, Copying, Top
        !            83: @chapter Overview
        !            84: @cindex overview
        !            85: 
        !            86: @code{Gzip} reduces the size of the named files using Lempel-Ziv coding
        !            87: (LZ77).  Whenever possible, each file is replaced by one with the
        !            88: extension ".z", while keeping the same ownership modes, access and
        !            89: modification times.  (The extension is "-z" for VMS, "z" for MSDOS, OS/2
        !            90: and Atari.)  If no files are specified, the standard input is compressed
        !            91: to the standard output. If the new file name is too long, @code{gzip}
        !            92: truncates it and keeps the original file name in the compressed file.
        !            93: @code{gzip} will only attempt to compress regular files.  In particular,
        !            94: it will ignore symbolic links.
        !            95: 
        !            96: Compressed files can be restored to their original form using
        !            97: "@code{gzip} -d" or @code{gunzip} or @code{zcat}.
        !            98: 
        !            99: @code{gunzip} takes a list of files on its command line and replaces
        !           100: each file whose name ends with ".z" or ".Z" and which begins with the
        !           101: correct magic number with an uncompressed file without the original
        !           102: extension.  @code{gunzip} also recognizes the special extensions ".tgz"
        !           103: and ".taz" as shorthands for ".tar.z" or ".tar.Z".
        !           104: 
        !           105: @code{gunzip} can currently decompress files created by @code{gzip},
        !           106: @code{zip}, @code{compress} or @code{pack}. The detection of the input
        !           107: format is automatic.  When using the first two formats, @code{gunzip}
        !           108: checks a 32 bit CRC (cyclic redundancy check). For @code{pack},
        !           109: @code{gunzip} checks the uncompressed length. The @code{compress}
        !           110: format was not designed to allow consistency checks. However @code{gunzip}
        !           111: is sometimes able to detect a bad .Z file. If you get an error
        !           112: when uncompressing a .Z file, do not assume that the .Z file is
        !           113: correct simply because the standard @code{uncompress} does not complain.
        !           114: This generally means that the standard @code{uncompress} does not check its
        !           115: input, and happily generates garbage output.
        !           116: 
        !           117: Files created by @code{zip} can be uncompressed by @code{gzip} only if
        !           118: they have a single member compressed with the 'deflation' method. This
        !           119: feature is only intended to help conversion of @code{tar.zip} files to
        !           120: the @code{tar.z} format. To extract @code{zip} files with several
        !           121: members, use @code{unzip} instead of @code{gunzip}.
        !           122: 
        !           123: @code{zcat} is identical to "@code{gunzip} -c".  @code{zcat}
        !           124: uncompresses either a list of files on the command line or its standard
        !           125: input and writes the uncompressed data on standard output.  @code{zcat}
        !           126: will uncompress files that have the correct magic number whether they
        !           127: have a ".z" suffix or not.
        !           128: 
        !           129: @code{gzip} uses the Lempel-Ziv algorithm used in @code{zip} and PKZIP.
        !           130: The amount of compression obtained depends on the size of the input and
        !           131: the distribution of common substrings.  Typically, text such as source
        !           132: code or English is reduced by 60-70%.  Compression is generally much
        !           133: better than that achieved by LZW (as used in @code{compress}), Huffman
        !           134: coding (as used in @code{pack}), or adaptive Huffman coding
        !           135: (@code{compact}).
        !           136: 
        !           137: Compression is always performed, even if the compressed file is slightly
        !           138: larger than the original. The worst case expansion is a few bytes for
        !           139: the gzip file header, plus 5 bytes every 32K block, or an expansion
        !           140: ratio of 0.015% for large files.  @code{gzip} preserves the mode,
        !           141: ownership and timestamps of files when compressing or decompressing.
        !           142: 
        !           143: @node Sample, Invoking gzip, Overview, Top
        !           144: @chapter Sample Output
        !           145: @cindex sample
        !           146: 
        !           147: Here are some realistic examples of running @code{gzip}.
        !           148: 
        !           149: This is the output of the command @samp{gzip}:
        !           150: 
        !           151: @example
        !           152: usage: gzip [-cdfhLrv19] [file ...]
        !           153: For more help, type: gzip -h
        !           154: @end example
        !           155: 
        !           156: This is the output of the command @samp{gzip -h}:
        !           157: 
        !           158: @example
        !           159: gzip 1.0.5 (4 Mar 93)
        !           160: usage: gzip [-cdfhLrtvV19] [file ...]
        !           161:  -c --stdout      write on standard output, keep original files unchanged
        !           162:  -d --decompress  decompress
        !           163:  -f --force       force overwrite of output file and compress links
        !           164:  -h --help        give this help
        !           165:  -L --license     display software license
        !           166:  -q --quiet       suppress all warnings
        !           167:  -r --recurse     recurse through directories
        !           168:  -t --test        test compressed file integrity (implies -d)
        !           169:  -v --verbose     verbose mode
        !           170:  -V --version     display version number
        !           171:  -1 --fast        compress faster
        !           172:  -9 --best        compress better
        !           173:  file...          files to (de)compress. If none given, use standard input
        !           174: @end example
        !           175: 
        !           176: This is the output of the command @samp{gzip -v gzip.c}:
        !           177: 
        !           178: @example
        !           179: gzip.c:                 69.8% -- replaced with gzip.c.z
        !           180: @end example
        !           181: 
        !           182: @node Invoking gzip, Advanced usage, Sample, Top
        !           183: @chapter Invoking @code{gzip}
        !           184: @cindex invoking
        !           185: @cindex options
        !           186: 
        !           187: The format for running the @code{gzip} program is:
        !           188: 
        !           189: @example
        !           190: gzip @var{option} @dots{}
        !           191: @end example
        !           192: 
        !           193: @code{gzip} supports the following options:
        !           194: 
        !           195: @table @samp
        !           196: @item --help
        !           197: @itemx -h
        !           198: Print an informative help message describing the options.
        !           199: 
        !           200: @item --stdout
        !           201: @itemx -c
        !           202: Write output on standard output; keep original files unchanged.
        !           203: If there are several input files, the output consists of a sequence of
        !           204: independently compressed members. To obtain better compression,
        !           205: concatenate all input files before compressing them.
        !           206: 
        !           207: @item --decompress
        !           208: @itemx -d
        !           209: Decompress.
        !           210: 
        !           211: @item --force
        !           212: @itemx -f
        !           213: Force compression or decompression even if the file has multiple links
        !           214: or the corresponding file already exists. If -f is not given, and
        !           215: when not running in the background, @code{gzip} prompts to verify
        !           216: whether an existing file should be overwritten.
        !           217: 
        !           218: @item --help
        !           219: @itemx -h
        !           220: Display a help screen.
        !           221: 
        !           222: @item --license
        !           223: @itemx -L
        !           224: Display the @code{gzip} license.
        !           225: 
        !           226: @item --recurse
        !           227: @itemx -r
        !           228: Travel the directory structure recursively. If any of the file names
        !           229: specified on the command line are directories, @code{gzip} will descend
        !           230: into the directory and compress all the files it finds there (or
        !           231: decompress them in the case of @code{gunzip}).
        !           232: 
        !           233: @item --test
        !           234: @itemx -t
        !           235: Test. Check the compressed file integrity.
        !           236: 
        !           237: @item --verbose
        !           238: @itemx -v
        !           239: Verbose. Display the name and percentage reduction for each file compressed.
        !           240: 
        !           241: @item --version
        !           242: @itemx -V
        !           243: Version. Display the version number and compilation options.
        !           244: 
        !           245: @item --fast
        !           246: @itemx --best
        !           247: @itemx -#
        !           248: Regulate the speed of compression using the specified digit #, where -1
        !           249: or --fast indicates the fastest compression method (less compression)
        !           250: and --best or -9 indicates the slowest compression method (optimal
        !           251: compression).  The default compression level is -5.
        !           252: @end table
        !           253: 
        !           254: @node Advanced usage, Environment, Invoking gzip, Top
        !           255: @chapter Advanced usage
        !           256: @cindex concatenated files
        !           257: 
        !           258: Multiple compressed files can be concatenated. In this case,
        !           259: @code{gunzip} will extract all members at once. If one member is
        !           260: damaged, other members might still be recovered after removal of the
        !           261: damaged member. Better compression can be usually obtained if all
        !           262: members are decompressed then recompressed in a single step.
        !           263: 
        !           264: This is an example of concatenating gzip files:
        !           265: 
        !           266: @example
        !           267: gzip -c file1  > foo.z
        !           268: gzip -c file2 >> foo.z
        !           269: @end example
        !           270: 
        !           271: Then
        !           272: 
        !           273: @example
        !           274: gunzip -c foo
        !           275: @end example
        !           276: 
        !           277: is equivalent to
        !           278: 
        !           279: @example
        !           280: cat file1 file2
        !           281: @end example
        !           282: 
        !           283: In case of damage to one member of a .z file, other members can
        !           284: still be recovered (if the damaged member is removed). However,
        !           285: you can get better compression by compressing all members at once:
        !           286: 
        !           287: @example
        !           288: cat file1 file2 | gzip > foo.z
        !           289: @end example
        !           290: 
        !           291: compresses better than
        !           292: 
        !           293: @example
        !           294: gzip -c file1 file2 > foo.z
        !           295: @end example
        !           296: 
        !           297: If you want to recompress concatenated files to get better compression, do:
        !           298: 
        !           299: @example
        !           300: zcat old.z | gzip > new.z
        !           301: @end example
        !           302: 
        !           303: @node Environment, Problems, Advanced usage, Top
        !           304: @chapter Environment
        !           305: @cindex Environment
        !           306: 
        !           307: The environment variable @code{GZIP} can hold a set of default options for
        !           308: gzip.  These options are interpreted first and can be ovewritten by
        !           309: explicit command line parameters.  For example:
        !           310: 
        !           311: @example
        !           312: for sh:    GZIP="-8 -v"; export GZIP
        !           313: for csh:   setenv GZIP "-8 -v"
        !           314: for MSDOS: set GZIP=-8 -v
        !           315: @end example
        !           316: 
        !           317: On Vax/VMS, the name of the environment variable is @code{GZIP_OPT}, to
        !           318: avoid a conflict with the symbol set for invocation of the program.
        !           319: 
        !           320: @node Problems, Concept Index, Environment, Top
        !           321: @chapter Reporting Bugs
        !           322: @cindex bugs
        !           323: 
        !           324: If you find a bug in @code{gzip}, please send electronic mail to
        !           325: @w{@samp{jloup@@chorus.fr}} or, if this fails, to
        !           326: @w{@samp{bug-gnu-utils@@prep.ai.mit.edu}}.  Include the version number,
        !           327: which you can find by running @w{@samp{gzip -V}}.  Also include in your
        !           328: message the hardware and operating system, the compiler used to compile,
        !           329: a description of the bug behavior, and the input to gzip that triggered
        !           330: the bug.@refill
        !           331: 
        !           332: @node Concept Index, , Problems, Top
        !           333: @unnumbered Concept Index
        !           334: 
        !           335: @printindex cp
        !           336: 
        !           337: @shortcontents
        !           338: @contents
        !           339: @bye

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