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Annotation of coherent/g/usr/bin/gzip/gzip.1, revision 1.1

1.1     ! root        1: .PU
        !             2: .TH GZIP 1 local
        !             3: .SH NAME
        !             4: gzip, gunzip, zcat \- compress or expand files
        !             5: .SH SYNOPSIS
        !             6: .ll +8
        !             7: .B gzip
        !             8: .RB [ " \-cdfhLrtvV19 " ]
        !             9: [
        !            10: .I "name \&..."
        !            11: ]
        !            12: .ll -8
        !            13: .br
        !            14: .B gunzip
        !            15: .RB [ " \-cfhLrtvV " ]
        !            16: [
        !            17: .I "name \&..."
        !            18: ]
        !            19: .br
        !            20: .B zcat
        !            21: .RB [ " \-hLV " ]
        !            22: [
        !            23: .I "name \&..."
        !            24: ]
        !            25: .SH DESCRIPTION
        !            26: .I Gzip
        !            27: reduces the size of the named files using Lempel-Ziv coding (LZ77).
        !            28: Whenever possible,
        !            29: each file is replaced by one with the extension
        !            30: .B "\&.z,"
        !            31: while keeping the same ownership modes, access and modification times.
        !            32: (The extension is
        !            33: .B "\-z"
        !            34: for VMS,
        !            35: .B "z"
        !            36: for MSDOS, OS/2 and Atari.)
        !            37: If no files are specified, the standard input is compressed to the
        !            38: standard output. If the new file name is too long,
        !            39: .I gzip
        !            40: truncates it and keeps the original file name in the compressed file.
        !            41: .I Gzip
        !            42: will only attempt to compress regular files.
        !            43: In particular, it will ignore symbolic links.
        !            44: .PP
        !            45: Compressed files can be restored to their original form using
        !            46: .I gzip -d
        !            47: or
        !            48: .I gunzip
        !            49: or
        !            50: .I zcat.
        !            51: .PP
        !            52: .I gunzip
        !            53: takes a list of files on its command line and replaces each
        !            54: file whose name ends with
        !            55: .B "\&.z"
        !            56: or
        !            57: .B "\&.Z"
        !            58: or
        !            59: .B "\&-z"
        !            60: and which begins with the correct magic number with an uncompressed
        !            61: file without the original extension.
        !            62: .I gunzip
        !            63: also recognizes the special extensions
        !            64: .B "\&.tgz"
        !            65: and
        !            66: .B "\&.taz"
        !            67: as shorthands for
        !            68: .B "\&.tar.z"
        !            69: or
        !            70: .B "\&.tar.Z"
        !            71: .PP
        !            72: .I gunzip
        !            73: can currently decompress files created by
        !            74: .I gzip, zip, compress
        !            75: or
        !            76: .I pack.
        !            77: The detection of the input format is automatic.  When using
        !            78: the first two formats,
        !            79: .I gunzip
        !            80: checks a 32 bit CRC. For
        !            81: .I pack, gunzip
        !            82: checks the uncompressed length. The
        !            83: .I compress
        !            84: format was not designed to allow consistency checks. However
        !            85: .I gunzip
        !            86: is sometimes able to detect a bad .Z file. If you get an error
        !            87: when uncompressing a .Z file, do not assume that the .Z file is
        !            88: correct simply because the standard
        !            89: .I uncompress
        !            90: does not complain. This generally means that the standard
        !            91: .I uncompress
        !            92: does not check its input, and happily generates garbage output.
        !            93: .PP
        !            94: Files created by
        !            95: .I zip
        !            96: can be uncompressed by gzip only if they have a single member compressed
        !            97: with the 'deflation' method. This feature is only intended to help
        !            98: conversion of tar.zip files to the tar.z format. To extract zip files
        !            99: with several members, use
        !           100: .I unzip
        !           101: instead of
        !           102: .I gunzip.
        !           103: .PP
        !           104: .I zcat
        !           105: is identical to
        !           106: .I gunzip
        !           107: .B \-c.
        !           108: (On some systems,
        !           109: .I zcat
        !           110: may be installed as
        !           111: .I gzcat
        !           112: to preserve the original link to
        !           113: .I compress.)
        !           114: .I zcat
        !           115: uncompresses either a list of files on the command line or its
        !           116: standard input and writes the uncompressed data on standard output.
        !           117: .I zcat
        !           118: will uncompress files that have the correct magic number whether
        !           119: they have a
        !           120: .B "\&.z"
        !           121: suffix or not.
        !           122: .PP
        !           123: .I Gzip
        !           124: uses the Lempel-Ziv algorithm used in
        !           125: .I zip
        !           126: and PKZIP.
        !           127: The amount of compression obtained depends on the size of the
        !           128: input and the distribution of common substrings.
        !           129: Typically, text such as source code or English
        !           130: is reduced by 60\-70%.
        !           131: Compression is generally much better than that achieved by
        !           132: LZW (as used in 
        !           133: .IR compress ),
        !           134: Huffman coding (as used in
        !           135: .IR pack ),
        !           136: or adaptive Huffman coding
        !           137: .RI ( compact ).
        !           138: .PP
        !           139: Compression is always performed, even if the compressed file is
        !           140: slightly larger than the original. The worst case expansion is
        !           141: a few bytes for the gzip file header, plus 5 bytes every 32K block,
        !           142: or an expansion ratio of 0.015% for large files.
        !           143: .I gzip
        !           144: preserves the mode, ownership and timestamps of files when compressing
        !           145: or decompressing.
        !           146: 
        !           147: .SH OPTIONS
        !           148: .TP
        !           149: .B \-c --stdout
        !           150: Write output on standard output; keep original files unchanged.
        !           151: If there are several input files, the output consists of a sequence of
        !           152: independently compressed members. To obtain better compression,
        !           153: concatenate all input files before compressing them.
        !           154: .TP
        !           155: .B \-d --decompress
        !           156: Decompress.
        !           157: .TP
        !           158: .B \-f --force
        !           159: Force compression or decompression even if the file has multiple links
        !           160: or the corresponding file already exists.
        !           161: If
        !           162: .B \-f
        !           163: is not given,
        !           164: and when not running in the background,
        !           165: .I gzip
        !           166: prompts to verify whether an existing file should be overwritten.
        !           167: .TP
        !           168: .B \-h --help
        !           169: Display a help screen.
        !           170: .TP
        !           171: .B \-L --license
        !           172: Display the
        !           173: .I gzip
        !           174: license.
        !           175: .TP
        !           176: .B \-q --quiet
        !           177: Suppress all warnings.
        !           178: .TP
        !           179: .B \-r --recurse
        !           180: Travel the directory structure recursively. If any of the file names
        !           181: specified on the command line are directories, 
        !           182: .I gzip
        !           183: will descend into the directory and compress all the files it finds there
        !           184: (or decompress them in the case of
        !           185: .I gunzip
        !           186: ).
        !           187: .TP
        !           188: .B \-t --test
        !           189: Test. Check the compressed file integrity.
        !           190: .TP
        !           191: .B \-v --verbose
        !           192: Verbose. Display the name and percentage reduction for each file compressed.
        !           193: .TP
        !           194: .B \-V --version
        !           195: Version. Display the version number and compilation options.
        !           196: .TP
        !           197: .B \-# --fast --best
        !           198: Regulate the speed of compression using the specified digit
        !           199: .IR # ,
        !           200: where
        !           201: .B \-1
        !           202: or
        !           203: .B \-\-fast
        !           204: indicates the fastest compression method (less compression)
        !           205: and
        !           206: .B \-9
        !           207: or
        !           208: .B \-\-best
        !           209: indicates the slowest compression method (optimal compression).
        !           210: The default compression level is
        !           211: .BR \-5.
        !           212: .SH "ADVANCED USAGE"
        !           213: Multiple compressed files can be concatenated. In this case,
        !           214: .I gunzip
        !           215: will extract all members at once. For example:
        !           216: 
        !           217:       gzip -c file1  > foo.z
        !           218:       gzip -c file2 >> foo.z
        !           219: Then
        !           220:       gunzip -c foo
        !           221: 
        !           222: is equivalent to
        !           223: 
        !           224:       cat file1 file2
        !           225: 
        !           226: In case of damage to one member of a .z file, other members can
        !           227: still be recovered (if the damaged member is removed). However,
        !           228: you can get better compression by compressing all members at once:
        !           229: 
        !           230:       cat file1 file2 | gzip > foo.z
        !           231: 
        !           232: compresses better than
        !           233: 
        !           234:       gzip -c file1 file2 > foo.z
        !           235: 
        !           236: If you want to recompress concatenated files to get better compression, do:
        !           237: 
        !           238:       zcat old.z | gzip > new.z
        !           239: .SH "ENVIRONMENT"
        !           240: The environment variable
        !           241: .B GZIP
        !           242: can hold a set of default options for
        !           243: .I gzip.
        !           244: These options are interpreted first and can be ovewritten by
        !           245: explicit command line parameters. For example:
        !           246:       for sh:    GZIP="-8 -v"; export GZIP
        !           247:       for csh:   setenv GZIP "-8 -v"
        !           248:       for MSDOS: set GZIP=-8 -v
        !           249: 
        !           250: On Vax/VMS, the name of the environment variable is GZIP_OPT, to
        !           251: avoid a conflict with the symbol set for invocation of the program.
        !           252: .SH "SEE ALSO"
        !           253: znew(1), zcmp(1), zmore(1), zforce(1), gzexe(1), zip(1), unzip(1), compress(1),
        !           254: pack(1), compact(1)
        !           255: .SH "DIAGNOSTICS"
        !           256: Exit status is normally 0;
        !           257: if an error occurs, exit status is 1. If a warning occurs, exit status is 2.
        !           258: .PP
        !           259: Usage: gzip [-cdfhLrtvV19] [file ...]
        !           260: .in +8
        !           261: Invalid options were specified on the command line.
        !           262: .in -8
        !           263: .IR file :
        !           264: not in gzip format
        !           265: .in +8
        !           266: The file specified to
        !           267: .I gunzip
        !           268: has not been compressed.
        !           269: .in -8
        !           270: .IR file:
        !           271: Corrupt input. Use zcat to recover some data.
        !           272: .in +8
        !           273: The compressed file has been damaged. The data up to the point of failure
        !           274: can be recovered using
        !           275: .in +8
        !           276: zcat file > recover
        !           277: .in -16
        !           278: .IR file :
        !           279: compressed with 
        !           280: .I xx
        !           281: bits, can only handle 
        !           282: .I yy
        !           283: bits
        !           284: .in +8
        !           285: .I File
        !           286: was compressed (using LZW) by a program that could deal with
        !           287: more 
        !           288: .I bits
        !           289: than the decompress code on this machine.
        !           290: Recompress the file with gzip, which compresses better and uses
        !           291: less memory.
        !           292: .in -8
        !           293: .IR file :
        !           294: already has z suffix -- no change
        !           295: .in +8
        !           296: The file is assumed to be already compressed.
        !           297: Rename the file and try again or use zcat.
        !           298: .in -8
        !           299: .I file
        !           300: already exists; do you wish to overwrite (y or n)?
        !           301: .in +8
        !           302: Respond "y" if you want the output file to be replaced; "n" if not.
        !           303: .in -8
        !           304: gunzip: corrupt input
        !           305: .in +8
        !           306: A SIGSEGV violation was detected which usually means that the input file has
        !           307: been corrupted.
        !           308: .in -8
        !           309: .I "xx.x%"
        !           310: .in +8
        !           311: Percentage of the input saved by compression.
        !           312: (Relevant only for
        !           313: .BR \-v \.)
        !           314: .in -8
        !           315: -- not a regular file or directory: ignored
        !           316: .in +8
        !           317: When the input file is not a regular file or directory,
        !           318: (e.g. a symbolic link, socket, FIFO, device file), it is
        !           319: left unaltered.
        !           320: .in -8
        !           321: -- has 
        !           322: .I xx 
        !           323: other links: unchanged
        !           324: .in +8
        !           325: The input file has links; it is left unchanged.  See
        !           326: .IR ln "(1)"
        !           327: for more information. Use the
        !           328: .B \-f
        !           329: flag to force compression of multiply-linked files.
        !           330: .in -8
        !           331: .SH CAVEATS
        !           332: The .z extension is already used by
        !           333: .IR pack "(1)".
        !           334: You can link
        !           335: .I gzip
        !           336: to
        !           337: .I pcat
        !           338: to get transparent decompression for programs expecting .z files to be in
        !           339: .IR pack
        !           340: format.

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