X-Git-Url: https://git.gag.com/?p=debian%2Fgzip;a=blobdiff_plain;f=gzip.doc;h=0286afa83f853109f664be687dd53e3615934e9c;hp=91dbb6dcbcd116112e5ee30d96d277e9f86838f7;hb=659cae49714b93487242525dfa0e5737463d78d8;hpb=302189d124ed5849c2589ea92e912eb24fdc4ab3 diff --git a/gzip.doc b/gzip.doc index 91dbb6d..0286afa 100644 --- a/gzip.doc +++ b/gzip.doc @@ -1,432 +1,385 @@ +GZIP(1) General Commands Manual GZIP(1) + +1mNAME0m + gzip, gunzip, zcat - compress or expand files + +1mSYNOPSIS0m + 1mgzip 22m[ 1m-acdfhklLnNrtvV19 22m] [1m-S suffix22m] [ 4mname24m 4m...24m ] + 1mgunzip 22m[ 1m-acfhklLnNrtvV 22m] [1m-S suffix22m] [ 4mname24m 4m...24m ] + 1mzcat 22m[ 1m-fhLV 22m] [ 4mname24m 4m...24m ] + +1mDESCRIPTION0m + 4mGzip24m reduces the size of the named files using Lempel-Ziv coding + (LZ77). Whenever possible, each file is replaced by one with the + extension 1m.gz22m, while keeping the same ownership modes, access and modi- + fication times. (The default extension is 1mz 22mfor MSDOS, OS/2 FAT, Win- + dows NT FAT and Atari.) If no files are specified, or if a file name + is "-", the standard input is compressed to the standard output. 4mGzip0m + will only attempt to compress regular files. In particular, it will + ignore symbolic links. + + If the compressed file name is too long for its file system, 4mgzip24m trun- + cates it. 4mGzip24m attempts to truncate only the parts of the file name + longer than 3 characters. (A part is delimited by dots.) If the name + consists of small parts only, the longest parts are truncated. For + example, if file names are limited to 14 characters, gzip.msdos.exe is + compressed to gzi.msd.exe.gz. Names are not truncated on systems which + do not have a limit on file name length. + + By default, 4mgzip24m keeps the original file name and timestamp in the com- + pressed file. These are used when decompressing the file with the 1m-N0m + option. This is useful when the compressed file name was truncated or + when the timestamp was not preserved after a file transfer. + + Compressed files can be restored to their original form using 4mgzip24m 4m-d0m + or 4mgunzip24m or 4mzcat24m. If the original name saved in the compressed file + is not suitable for its file system, a new name is constructed from the + original one to make it legal. + + 4mgunzip24m takes a list of files on its command line and replaces each file + whose name ends with .gz, -gz, .z, -z, or _z (ignoring case) and which + begins with the correct magic number with an uncompressed file without + the original extension. 4mgunzip24m also recognizes the special extensions + 1m.tgz 22mand 1m.taz 22mas shorthands for 1m.tar.gz 22mand 1m.tar.Z 22mrespectively. When + compressing, 4mgzip24m uses the 1m.tgz 22mextension if necessary instead of trun- + cating a file with a 1m.tar 22mextension. + + 4mgunzip24m can currently decompress files created by 4mgzip24m, 4mzip24m, 4mcompress24m, + 4mcompress24m 4m-H24m or 4mpack24m. The detection of the input format is automatic. + When using the first two formats, 4mgunzip24m checks a 32 bit CRC. For 4mpack0m + and 4mgunzip24m checks the uncompressed length. The standard 4mcompress24m format + was not designed to allow consistency checks. However 4mgunzip24m is some- + times able to detect a bad .Z file. If you get an error when uncom- + pressing a .Z file, do not assume that the .Z file is correct simply + because the standard 4muncompress24m does not complain. This generally means + that the standard 4muncompress24m does not check its input, and happily gen- + erates garbage output. The SCO compress -H format (lzh compression + method) does not include a CRC but also allows some consistency checks. + + Files created by 4mzip24m can be uncompressed by gzip only if they have a + single member compressed with the 'deflation' method. This feature is + only intended to help conversion of tar.zip files to the tar.gz format. + To extract a 4mzip24m file with a single member, use a command like 4mgunzip0m + 4m foo.gz + gzip -c file2 >> foo.gz + + Then + + gunzip -c foo + + is equivalent to + + cat file1 file2 + + In case of damage to one member of a .gz file, other members can still + be recovered (if the damaged member is removed). However, you can get + better compression by compressing all members at once: + + cat file1 file2 | gzip > foo.gz + + compresses better than + + gzip -c file1 file2 > foo.gz + + If you want to recompress concatenated files to get better compression, + do: + + gzip -cd old.gz | gzip > new.gz + + If a compressed file consists of several members, the uncompressed size + and CRC reported by the --list option applies to the last member only. + If you need the uncompressed size for all members, you can use: + + gzip -cd file.gz | wc -c + + If you wish to create a single archive file with multiple members so + that members can later be extracted independently, use an archiver such + as tar or zip. GNU tar supports the -z option to invoke gzip transpar- + ently. gzip is designed as a complement to tar, not as a replacement. + +1mENVIRONMENT0m + The obsolescent environment variable 1mGZIP 22mcan hold a set of default + options for 4mgzip24m. These options are interpreted first and can be over- + written by explicit command line parameters. As this can cause prob- + lems when using scripts, this feature is supported only for options + that are reasonably likely to not cause too much harm, and 4mgzip24m warns + if it is used. This feature will be removed in a future release of + 4mgzip24m. + + You can use an alias or script instead. For example, if 4mgzip24m is in the + directory 1m/usr/bin 22myou can prepend 1m$HOME/bin 22mto your 1mPATH 22mand create an + executable script 1m$HOME/bin/gzip 22mcontaining the following: + + #! /bin/sh + export PATH=/usr/bin + exec gzip -9 "$@" + +1mSEE ALSO0m + znew(1), zcmp(1), zmore(1), zforce(1), gzexe(1), zip(1), unzip(1), com- + press(1) + + The 4mgzip24m file format is specified in P. Deutsch, GZIP file format spec- + ification version 4.3, 1m22m, Internet + RFC 1952 (May 1996). The 4mzip24m deflation format is specified in P. + Deutsch, DEFLATE Compressed Data Format Specification version 1.3, + 1m22m, Internet RFC 1951 (May 1996). -User Commands GZIP(1) - -NAME - gzip, gunzip, zcat - compress or expand files - -SYNOPSIS - gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ... ] - gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ... ] - zcat [ -fhLV ] [ name ... ] - -DESCRIPTION - Gzip reduces the size of the named files using Lempel-Ziv - coding (LZ77). Whenever possible, each file is replaced by - one with the extension .gz, while keeping the same ownership - modes, access and modification times. (The default exten- - sion is -gz for VMS, z for MSDOS, OS/2 FAT, Windows NT FAT - and Atari.) If no files are specified, or if a file name is - "-", the standard input is compressed to the standard out- - put. Gzip will only attempt to compress regular files. In - particular, it will ignore symbolic links. - - If the compressed file name is too long for its file system, - gzip truncates it. Gzip attempts to truncate only the parts - of the file name longer than 3 characters. (A part is - delimited by dots.) If the name consists of small parts - only, the longest parts are truncated. For example, if file - names are limited to 14 characters, gzip.msdos.exe is com- - pressed to gzi.msd.exe.gz. Names are not truncated on sys- - tems which do not have a limit on file name length. - - By default, gzip keeps the original file name and timestamp - in the compressed file. These are used when decompressing - the file with the -N option. This is useful when the com- - pressed file name was truncated or when the time stamp was - not preserved after a file transfer. - - Compressed files can be restored to their original form - using gzip -d or gunzip or zcat. If the original name saved - in the compressed file is not suitable for its file system, - a new name is constructed from the original one to make it - legal. - - gunzip takes a list of files on its command line and - replaces each file whose name ends with .gz, -gz, .z, -z, _z - or .Z and which begins with the correct magic number with an - uncompressed file without the original extension. gunzip - also recognizes the special extensions .tgz and .taz as - shorthands for .tar.gz and .tar.Z respectively. When com- - pressing, gzip uses the .tgz extension if necessary instead - of truncating a file with a .tar extension. - - gunzip can currently decompress files created by gzip, zip, - compress, compress -H or pack. The detection of the input - format is automatic. When using the first two formats, - -SunOS 5.8 Last change: local 1 - -User Commands GZIP(1) - - gunzip checks a 32 bit CRC. For pack, gunzip checks the - uncompressed length. The standard compress format was not - designed to allow consistency checks. However gunzip is - sometimes able to detect a bad .Z file. 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 out- - put. The SCO compress -H format (lzh compression method) - does not include a CRC but also allows some consistency - checks. - - Files created by zip can be uncompressed by gzip only if - they have a single member compressed with the 'deflation' - method. This feature is only intended to help conversion of - tar.zip files to the tar.gz format. To extract zip files - with several members, use unzip instead of gunzip. - - zcat is identical to gunzip -c. (On some systems, zcat may - be installed as gzcat to preserve the original link to com- - press.) zcat uncompresses either a list of files on the - command line or its standard input and writes the uncom- - pressed data on standard output. zcat will uncompress files - that have the correct magic number whether they have a .gz - suffix or not. - - Gzip uses the Lempel-Ziv algorithm used in zip and PKZIP. - The amount of compression obtained depends on the size of - the input and the distribution of common substrings. Typi- - cally, text such as source code or English is reduced by - 60-70%. Compression is generally much better than that - achieved by LZW (as used in compress), Huffman coding (as - used in pack), or adaptive Huffman coding (compact). - - Compression is always performed, even if the compressed file - is slightly larger than the original. The worst case expan- - sion is a few bytes for the gzip file header, plus 5 bytes - every 32K block, or an expansion ratio of 0.015% for large - files. Note that the actual number of used disk blocks - almost never increases. gzip preserves the mode, ownership - and timestamps of files when compressing or decompressing. - -OPTIONS - -a --ascii - Ascii text mode: convert end-of-lines using local con- - ventions. This option is supported only on some non- - Unix systems. For MSDOS, CR LF is converted to LF when - compressing, and LF is converted to CR LF when decom- - pressing. - - -c --stdout --to-stdout - -SunOS 5.8 Last change: local 2 - -User Commands GZIP(1) - - Write output on standard output; keep original files - unchanged. If there are several input files, the out- - put consists of a sequence of independently compressed - members. To obtain better compression, concatenate all - input files before compressing them. - - -d --decompress --uncompress - Decompress. - - -f --force - Force compression or decompression even if the file has - multiple links or the corresponding file already - exists, or if the compressed data is read from or writ- - ten to a terminal. If the input data is not in a format - recognized by gzip, and if the option --stdout is also - given, copy the input data without change to the stan- - dard ouput: let zcat behave as cat. If -f is not - given, and when not running in the background, gzip - prompts to verify whether an existing file should be - overwritten. - - -h --help - Display a help screen and quit. - - -l --list - For each compressed file, list the following fields: - - compressed size: size of the compressed file - uncompressed size: size of the uncompressed file - ratio: compression ratio (0.0% if unknown) - uncompressed_name: name of the uncompressed file - - The uncompressed size is given as -1 for files not in - gzip format, such as compressed .Z files. To get the - uncompressed size for such a file, you can use: - - zcat file.Z | wc -c - - In combination with the --verbose option, the following - fields are also displayed: - - method: compression method - crc: the 32-bit CRC of the uncompressed data - date & time: time stamp for the uncompressed file - - The compression methods currently supported are - deflate, compress, lzh (SCO compress -H) and pack. The - crc is given as ffffffff for a file not in gzip format. - - With --name, the uncompressed name, date and time are - those stored within the compress file if present. - -SunOS 5.8 Last change: local 3 - -User Commands GZIP(1) - - With --verbose, the size totals and compression ratio - for all files is also displayed, unless some sizes are - unknown. With --quiet, the title and totals lines are - not displayed. - - -L --license - Display the gzip license and quit. - - -n --no-name - When compressing, do not save the original file name - and time stamp by default. (The original name is always - saved if the name had to be truncated.) When decom- - pressing, do not restore the original file name if pre- - sent (remove only the gzip suffix from the compressed - file name) and do not restore the original time stamp - if present (copy it from the compressed file). This - option is the default when decompressing. +1mDIAGNOSTICS0m + Exit status is normally 0; if an error occurs, exit status is 1. If a + warning occurs, exit status is 2. + + Usage: gzip [-cdfhklLnNrtvV19] [-S suffix] [file ...] + Invalid options were specified on the command line. + + 4mfile24m: not in gzip format + The file specified to 4mgunzip24m has not been compressed. + + 4mfile24m: Corrupt input. Use zcat to recover some data. + The compressed file has been damaged. The data up to the point + of failure can be recovered using + + zcat 4mfile24m > recover - -N --name - When compressing, always save the original file name - and time stamp; this is the default. When decompress- - ing, restore the original file name and time stamp if - present. This option is useful on systems which have a - limit on file name length or when the time stamp has - been lost after a file transfer. + 4mfile24m: compressed with 4mxx24m bits, can only handle 4myy24m bits + 4mFile24m was compressed (using LZW) by a program that could deal + with more 4mbits24m than the decompress code on this machine. Recom- + press the file with gzip, which compresses better and uses less + memory. - -q --quiet - Suppress all warnings. + 4mfile24m: already has .gz suffix -- unchanged + The file is assumed to be already compressed. Rename the file + and try again. - -r --recursive - Travel the directory structure recursively. If any of - the file names specified on the command line are direc- - tories, gzip will descend into the directory and com- - press all the files it finds there (or decompress them - in the case of gunzip ). + 4mfile24m already exists; do you wish to overwrite (y or n)? + Respond "y" if you want the output file to be replaced; "n" if + not. - -S .suf --suffix .suf - Use suffix .suf instead of .gz. Any suffix can be - given, but suffixes other than .z and .gz should be - avoided to avoid confusion when files are transferred - to other systems. A null suffix forces gunzip to try - decompression on all given files regardless of suffix, - as in: + gunzip: corrupt input + A SIGSEGV violation was detected which usually means that the + input file has been corrupted. - gunzip -S "" * (*.* for MSDOS) + 4mxx.x%24m Percentage of the input saved by compression. + (Relevant only for 1m-v 22mand 1m-l22m.) - Previous versions of gzip used the .z suffix. This was - changed to avoid a conflict with pack(1). + -- not a regular file or directory: ignored + When the input file is not a regular file or directory, (e.g. a + symbolic link, socket, FIFO, device file), it is left unaltered. - -t --test - Test. Check the compressed file integrity. - -SunOS 5.8 Last change: local 4 - -User Commands GZIP(1) - - -v --verbose - Verbose. Display the name and percentage reduction for - each file compressed or decompressed. - - -V --version - Version. Display the version number and compilation - options then quit. - - -# --fast --best - Regulate the speed of compression using the specified - digit #, where -1 or --fast indicates the fastest com- - pression method (less compression) and -9 or --best - indicates the slowest compression method (best compres- - sion). The default compression level is -6 (that is, - biased towards high compression at expense of speed). - -ADVANCED USAGE - Multiple compressed files can be concatenated. In this case, - gunzip will extract all members at once. For example: - - gzip -c file1 > foo.gz - gzip -c file2 >> foo.gz - - Then - - gunzip -c foo - - is equivalent to - - cat file1 file2 - - In case of damage to one member of a .gz file, other members - can still be recovered (if the damaged member is removed). - However, you can get better compression by compressing all - members at once: - - cat file1 file2 | gzip > foo.gz - - compresses better than - - gzip -c file1 file2 > foo.gz - - If you want to recompress concatenated files to get better - compression, do: - - gzip -cd old.gz | gzip > new.gz - - If a compressed file consists of several members, the uncom- - pressed size and CRC reported by the --list option applies - to the last member only. If you need the uncompressed size - for all members, you can use: - -SunOS 5.8 Last change: local 5 - -User Commands GZIP(1) - - gzip -cd file.gz | wc -c - - If you wish to create a single archive file with multiple - members so that members can later be extracted indepen- - dently, use an archiver such as tar or zip. GNU tar supports - the -z option to invoke gzip transparently. gzip is designed - as a complement to tar, not as a replacement. - -ENVIRONMENT - The environment variable GZIP can hold a set of default - options for gzip. These options are interpreted first and - can be overwritten by explicit command line parameters. For - example: - for sh: GZIP="-8v --name"; export GZIP - for csh: setenv GZIP "-8v --name" - for MSDOS: set GZIP=-8v --name - - On Vax/VMS, the name of the environment variable is - GZIP_OPT, to avoid a conflict with the symbol set for invo- - cation of the program. - -SEE ALSO - znew(1), zcmp(1), zmore(1), zforce(1), gzexe(1), zip(1), - unzip(1), compress(1), pack(1), compact(1) - - The gzip file format is specified in P. Deutsch, GZIP file - format specification version 4.3, , Internet RFC 1952 (May 1996). The zip - deflation format is specified in P. Deutsch, DEFLATE Com- - pressed Data Format Specification version 1.3, - , Internet RFC 1951 - (May 1996). - -DIAGNOSTICS - Exit status is normally 0; if an error occurs, exit status - is 1. If a warning occurs, exit status is 2. - - Usage: gzip [-cdfhlLnNrtvV19] [-S suffix] [file ...] - Invalid options were specified on the command line. - - file: not in gzip format - The file specified to gunzip has not been compressed. - - file: Corrupt input. Use zcat to recover some data. - The compressed file has been damaged. The data up to - the point of failure can be recovered using - - zcat file > recover - - file: compressed with xx bits, can only handle yy bits - File was compressed (using LZW) by a program that could - deal with more bits than the decompress code on this - -SunOS 5.8 Last change: local 6 - -User Commands GZIP(1) - - machine. Recompress the file with gzip, which com- - presses better and uses less memory. - - file: already has .gz suffix -- no change - The file is assumed to be already compressed. Rename - the file and try again. - - file already exists; do you wish to overwrite (y or n)? - Respond "y" if you want the output file to be replaced; - "n" if not. - - gunzip: corrupt input - A SIGSEGV violation was detected which usually means - that the input file has been corrupted. - - xx.x% Percentage of the input saved by compression. - (Relevant only for -v and -l.) - - -- not a regular file or directory: ignored - When the input file is not a regular file or directory, - (e.g. a symbolic link, socket, FIFO, device file), it - is left unaltered. - - -- has xx other links: unchanged - The input file has links; it is left unchanged. See - ln(1) for more information. Use the -f flag to force - compression of multiply-linked files. - -CAVEATS - When writing compressed data to a tape, it is generally nec- - essary to pad the output with zeroes up to a block boundary. - When the data is read and the whole block is passed to gun- - zip for decompression, gunzip detects that there is extra - trailing garbage after the compressed data and emits a warn- - ing by default. You have to use the --quiet option to sup- - press the warning. This option can be set in the GZIP envi- - ronment variable as in: - for sh: GZIP="-q" tar -xfz --block-compress /dev/rst0 - for csh: (setenv GZIP -q; tar -xfz --block-compr /dev/rst0 - - In the above example, gzip is invoked implicitly by the -z - option of GNU tar. Make sure that the same block size (-b - option of tar) is used for reading and writing compressed - data on tapes. (This example assumes you are using the GNU - version of tar.) - -BUGS - The gzip format represents the the input size modulo 2^32, - so the --list option reports incorrect uncompressed sizes - and compression ratios for uncompressed files 4 GB and - larger. To work around this problem, you can use the fol- - lowing command to discover a large uncompressed file's true - -SunOS 5.8 Last change: local 7 - -User Commands GZIP(1) - - size: - - zcat file.gz | wc -c - - The --list option reports sizes as -1 and crc as ffffffff if - the compressed file is on a non seekable media. - - In some rare cases, the --best option gives worse compres- - sion than the default compression level (-6). On some highly - redundant files, compress compresses better than gzip. - -COPYRIGHT NOTICE - Copyright (C) 1998, 1999, 2001 Free Software Foundation, - Inc. - Copyright (C) 1992, 1993 Jean-loup Gailly - - Permission is granted to make and distribute verbatim copies - of this manual provided the copyright notice and this per- - mission notice are preserved on all copies. - - Permission is granted to copy and distribute modified ver- - sions of this manual under the conditions for verbatim copy- - ing, provided that the entire resulting derived work is dis- - tributed under the terms of a permission notice identical to - this one. - - Permission is granted to copy and distribute translations of - this manual into another language, under the above condi- - tions for modified versions, except that this permission - notice may be stated in a translation approved by the Foun- - dation. - -SunOS 5.8 Last change: local 8 + -- has 4mxx24m other links: unchanged + The input file has links; it is left unchanged. See 4mln24m(1) for + more information. Use the 1m-f 22mflag to force compression of multi- + ply-linked files. +1mCAVEATS0m + When writing compressed data to a tape, it is generally necessary to + pad the output with zeroes up to a block boundary. When the data is + read and the whole block is passed to 4mgunzip24m for decompression, 4mgunzip0m + detects that there is extra trailing garbage after the compressed data + and emits a warning by default. You can use the --quiet option to sup- + press the warning. + +1mBUGS0m + The gzip format represents the input size modulo 2^32, so the --list + option reports incorrect uncompressed sizes and compression ratios for + uncompressed files 4 GB and larger. To work around this problem, you + can use the following command to discover a large uncompressed file's + true size: + + zcat file.gz | wc -c + + The --list option reports sizes as -1 and crc as ffffffff if the com- + pressed file is on a non seekable media. + + In some rare cases, the --best option gives worse compression than the + default compression level (-6). On some highly redundant files, 4mcom-0m + 4mpress24m compresses better than 4mgzip24m. + +1mCOPYRIGHT NOTICE0m + Copyright (C) 1998-1999, 2001-2002, 2012, 2015-2018 Free Software Foun- + dation, Inc. + Copyright (C) 1992, 1993 Jean-loup Gailly + + Permission is granted to make and distribute verbatim copies of this + manual provided the copyright notice and this permission notice are + preserved on all copies. + + Permission is granted to copy and distribute modified versions of this + manual under the conditions for verbatim copying, provided that the + entire resulting derived work is distributed under the terms of a per- + mission notice identical to this one. + + Permission is granted to copy and distribute translations of this man- + ual into another language, under the above conditions for modified ver- + sions, except that this permission notice may be stated in a transla- + tion approved by the Foundation. + + local GZIP(1)