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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:43:11 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:43:11 +0000
commitfc22b3d6507c6745911b9dfcc68f1e665ae13dbc (patch)
treece1e3bce06471410239a6f41282e328770aa404a /upstream/fedora-rawhide/man1/gzip.1
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downloadmanpages-l10n-fc22b3d6507c6745911b9dfcc68f1e665ae13dbc.tar.xz
manpages-l10n-fc22b3d6507c6745911b9dfcc68f1e665ae13dbc.zip
Adding upstream version 4.22.0.upstream/4.22.0
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.TH GZIP 1 local
+.SH NAME
+gzip, gunzip, zcat \- compress or expand files
+.SH SYNOPSIS
+.ll +8
+.B gzip
+.RB [ " \-acdfhklLnNrtvV19 " ]
+.RB [ \-S\ suffix ]
+[
+.I "name \&..."
+]
+.ll -8
+.br
+.B gunzip
+.RB [ " \-acfhklLnNrtvV " ]
+.RB [ \-S\ suffix ]
+[
+.I "name \&..."
+]
+.br
+.B zcat
+.RB [ " \-fhLV " ]
+[
+.I "name \&..."
+]
+.SH DESCRIPTION
+The
+.B gzip
+command
+reduces the size of the named files using Lempel-Ziv coding (LZ77).
+Whenever possible,
+each file is replaced by one with the extension
+.BR "\&.gz" ,
+while keeping the same ownership modes, access and modification times.
+(The default extension is
+.B "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 output.
+The
+.B gzip
+command
+will only attempt to compress regular files.
+In particular, it will ignore symbolic links.
+.PP
+If the compressed file name is too long for its file system,
+.B gzip
+truncates it.
+The
+.B gzip
+command
+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.
+.PP
+By default,
+.B gzip
+keeps the original file name and timestamp in the compressed file.
+These are used when decompressing the file with the
+.B \-N
+option.
+This is useful when the compressed file name was truncated or
+when the timestamp was not preserved after a file transfer.
+.PP
+Compressed files can be restored to their original form using
+.B "gzip \-d"
+or
+.B gunzip
+or
+.BR 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 valid.
+.PP
+.B gunzip
+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.
+.B gunzip
+also recognizes the special extensions
+.B "\&.tgz"
+and
+.B "\&.taz"
+as shorthands for
+.B "\&.tar.gz"
+and
+.B "\&.tar.Z"
+respectively.
+When compressing,
+.B gzip
+uses the
+.B "\&.tgz"
+extension if necessary instead of truncating a file with a
+.B "\&.tar"
+extension.
+.PP
+.B gunzip
+can currently decompress files created by
+.BR gzip ,
+.BR zip ,
+.BR compress ,
+.B "compress \-H"
+or
+.BR pack .
+The detection of the input format is automatic.
+When using the first two formats,
+.B gunzip
+checks a 32 bit CRC.
+For
+.B pack
+and
+.B gunzip
+checks the uncompressed length.
+The standard
+.B compress
+format was not designed to allow consistency checks.
+However
+.B 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
+.B uncompress
+does not complain.
+This generally means that the standard
+.B uncompress
+does not check its input, and happily generates garbage output.
+The SCO compress \-H format (lzh compression method) does not include a CRC
+but also allows some consistency checks.
+.PP
+Files created by
+.B 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 a
+.B zip
+file with a single member, use a command like
+.RB ' "gunzip <foo.zip" '
+or
+.RB ' "gunzip \-S .zip foo.zip" '.
+To extract zip files
+with several members, use
+.B unzip
+instead of
+.BR gunzip .
+.PP
+The
+.B zcat
+command
+is identical to
+.B gunzip
+.BR \-c .
+(On some systems,
+.B zcat
+may be installed as
+.B gzcat
+to preserve the original link to
+.BR compress .)
+.B zcat
+uncompresses either a list of files on the command line or its
+standard input and writes the uncompressed data on standard output.
+.B zcat
+will uncompress files that have the correct magic number whether
+they have a
+.B "\&.gz"
+suffix or not.
+.PP
+The
+.B gzip
+command
+uses the Lempel-Ziv algorithm used in
+.B zip
+and PKZIP.
+The amount of compression obtained depends on the size of the
+input and the distribution of common substrings.
+Typically, text such as source code or English
+is reduced by 60\(en70%.
+Compression is generally much better than that achieved by
+LZW (as used in
+.BR compress ),
+Huffman coding (as used in
+.BR pack ),
+or adaptive Huffman coding
+.RB ( compact ).
+.PP
+Compression is always performed, even if the compressed file is
+slightly larger than the original.
+The worst case expansion is
+a few bytes for the gzip file header, plus 5 bytes per 32\ KiB block,
+or an expansion ratio of 0.015% for large files.
+The actual number of used disk blocks almost never increases.
+.PP
+.B gzip
+normally preserves the mode and modification timestamp
+of a file when compressing or decompressing.
+If you have appropriate privileges,
+it also preserves the file's owner and group.
+.SH OPTIONS
+.TP
+.B \-a \-\-ascii
+Ascii text mode: convert end-of-lines using local conventions.
+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 decompressing.
+.TP
+.B \-c \-\-stdout \-\-to-stdout
+Write output on standard output; keep original files unchanged.
+If there are several input files, the output consists of a sequence of
+independently compressed members.
+To obtain better compression,
+concatenate all input files before compressing them.
+.TP
+.B \-d \-\-decompress \-\-uncompress
+Decompress.
+.TP
+.B \-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 written to a terminal.
+If the input data is not in a format recognized by
+.BR gzip ,
+and if the option \-\-stdout is also given, copy the input data without change
+to the standard output: let
+.B zcat
+behave as
+.BR cat .
+If
+.B \-f
+is not given,
+and when not running in the background,
+.B gzip
+prompts to verify whether an existing file should be overwritten.
+.TP
+.B \-h \-\-help
+Display a help screen and quit.
+.TP
+.B \-k \-\-keep
+Keep (don't delete) input files during compression or decompression.
+.TP
+.B \-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: timestamp 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.
+
+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.
+.TP
+.B \-L \-\-license
+Display the
+.B gzip
+license and quit.
+.TP
+.B \-n \-\-no-name
+When compressing, do not save the original file name and timestamp by default.
+(The original name is always saved if the name had to be truncated.)
+When decompressing, do not restore the original file name
+if present (remove only the
+.B gzip
+suffix from the compressed file name) and do not restore the original
+timestamp if present (copy it from the compressed file).
+This option is the default when decompressing.
+.TP
+.B \-N \-\-name
+When compressing, always save the original file name, and save
+the seconds part of the original modification timestamp if the
+original is a regular file and its timestamp is at least 1 (1970-01-01
+00:00:01 UTC) and is less than 2**32 (2106-02-07 06:28:16 UTC,
+assuming leap seconds are not counted); this
+is the default.
+When decompressing, restore from the saved file name and
+timestamp if present.
+This option is useful on systems which have a limit on file name
+length or when the timestamp has been lost after a file transfer.
+.TP
+.B \-q \-\-quiet
+Suppress all warnings.
+.TP
+.B \-r \-\-recursive
+Travel the directory structure recursively.
+If any of the file names specified on the command line are directories,
+.B gzip
+will descend into the directory and compress all the files it finds there
+(or decompress them in the case of
+.B gunzip
+).
+.TP
+.B \-S .suf \-\-suffix .suf
+When compressing, use suffix .suf instead of .gz.
+Any non-empty suffix can be given, but suffixes
+other than .z and .gz should be avoided to avoid confusion when files
+are transferred to other systems.
+
+When decompressing, add .suf to the beginning of the list of
+suffixes to try, when deriving an output file name from an input file name.
+.TP
+.B \-\-synchronous
+Use synchronous output.
+With this option,
+.B gzip
+is less likely to lose data during a system crash, but it can be
+considerably slower.
+.TP
+.B \-t \-\-test
+Test.
+Check the compressed file integrity then quit.
+.TP
+.B \-v \-\-verbose
+Verbose.
+Display the name and percentage reduction for each file compressed
+or decompressed.
+.TP
+.B \-V \-\-version
+Version.
+Display the version number and compilation options then quit.
+.TP
+.B \-# \-\-fast \-\-best
+Regulate the speed of compression using the specified digit
+.BR # ,
+where
+.B \-1
+or
+.B \-\-fast
+indicates the fastest compression method (less compression)
+and
+.B \-9
+or
+.B \-\-best
+indicates the slowest compression method (best compression).
+The default compression level is
+.B \-6
+(that is, biased towards high compression at expense of speed).
+.TP
+.B \-\-rsyncable
+When you synchronize a compressed file between two computers,
+this option allows rsync to transfer only files that were changed in
+the archive instead of the entire archive.
+Normally, after a change is made to any file in the archive,
+the compression algorithm can generate a new version of the archive
+that does not match the previous version of the archive.
+In this case, rsync transfers the entire new version of the archive to
+the remote computer.
+With this option, rsync can transfer only the changed files as well as
+a small amount of metadata that is required to update the archive
+structure in the area that was changed.
+.SH "ADVANCED USAGE"
+Multiple compressed files can be concatenated.
+In this case,
+.B 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 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 transparently.
+gzip is designed as a complement to tar, not as a replacement.
+.SH "ENVIRONMENT"
+The obsolescent environment variable
+.B GZIP
+can hold a set of default options for
+.BR gzip .
+These options are interpreted first and can be overwritten by explicit
+command line parameters.
+As this can cause problems when using scripts,
+this feature is supported only for options that are
+reasonably likely to not cause too much harm, and
+.B gzip
+warns if it is used.
+This feature will be removed in a future release of
+.BR gzip .
+.PP
+You can use an alias or script instead.
+For example, if
+.B gzip
+is in the directory
+.B /usr/bin
+you can prepend
+.B $HOME/bin
+to your
+.B PATH
+and create an executable script
+.B $HOME/bin/gzip
+containing the following:
+
+ #! /bin/sh
+ export PATH=/usr/bin
+ exec gzip \-9 "$@"
+.SH "SEE ALSO"
+.BR znew (1),
+.BR zcmp (1),
+.BR zmore (1),
+.BR zforce (1),
+.BR gzexe (1),
+.BR zip (1),
+.BR unzip (1),
+.BR compress (1)
+.PP
+The
+.B gzip
+file format is specified in P. Deutsch, \s-1GZIP\s0 file format
+specification version 4.3,
+.BR <https://www.ietf.org/rfc/rfc1952.txt> ,
+Internet RFC 1952 (May 1996).
+The
+.B zip
+deflation format is specified in P. Deutsch, \s-1DEFLATE\s0 Compressed
+Data Format Specification version 1.3,
+.BR <https://www.ietf.org/rfc/rfc1951.txt> ,
+Internet RFC 1951 (May 1996).
+.SH "DIAGNOSTICS"
+Exit status is normally 0;
+if an error occurs, exit status is 1.
+If a warning occurs, exit status is 2.
+.TP
+Usage: gzip [\-cdfhklLnNrtvV19] [\-S suffix] [file ...]
+Invalid options were specified on the command line.
+.TP
+\fIfile\fP\^: not in gzip format
+The file specified to
+.B gunzip
+has not been compressed.
+.TP
+\fIfile\fP\^: 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 \fIfile\fP > recover
+.TP
+\fIfile\fP\^: compressed with \fIxx\fP bits, can only handle \fIyy\fP bits
+.B File
+was compressed (using LZW) by a program that could deal with
+more
+bits
+than the decompress code on this machine.
+Recompress the file with gzip, which compresses better and uses
+less memory.
+.TP
+\fIfile\fP\^: already has .gz suffix \-\- unchanged
+The file is assumed to be already compressed.
+Rename the file and try again.
+.TP
+\fIfile\fP already exists; do you wish to overwrite (y or n)?
+Respond "y" if you want the output file to be replaced; "n" if not.
+.TP
+gunzip: corrupt input
+A SIGSEGV violation was detected which usually means that the input file has
+been corrupted.
+.TP
+\fIxx.x%\fP Percentage of the input saved by compression.
+(Relevant only for
+.B \-v
+and
+.BR \-l \.)
+.TP
+\-\- 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.
+.TP
+\-\- has \fIxx\fP other links: unchanged
+The input file has links; it is left unchanged.
+See
+.BR ln "(1)"
+for more information.
+Use the
+.B \-f
+flag to force compression of multiply-linked files.
+.SH CAVEATS
+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
+.B gunzip
+for decompression,
+.B gunzip
+detects that there is extra trailing garbage after the compressed data
+and emits a warning by default.
+You can use the \-\-quiet option to suppress the warning.
+.SH BUGS
+In some rare cases, the \-\-best option gives worse compression than
+the default compression level (\-6).
+On some highly redundant files,
+.B compress
+compresses better than
+.BR gzip .
+.SH "REPORTING BUGS"
+Report bugs to: bug\-gzip@gnu.org
+.br
+GNU gzip home page: <https://www.gnu.org/software/gzip/>
+.br
+General help using GNU software: <https://www.gnu.org/gethelp/>
+.SH "COPYRIGHT NOTICE"
+Copyright \(co 1998\(en1999, 2001\(en2002, 2012, 2015\(en2023
+Free Software Foundation, Inc.
+.br
+Copyright \(co 1992, 1993 Jean-loup Gailly
+.PP
+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.
+.ig
+Permission is granted to process this file through troff and print the
+results, provided the printed document carries copying permission
+notice identical to this one except for the removal of this paragraph
+(this paragraph not being relevant to the printed manual).
+..
+.PP
+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 permission
+notice identical to this one.
+.PP
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions,
+except that this permission notice may be stated in a translation approved
+by the Foundation.