-GZIP(1) GZIP(1)
+GZIP(1) GZIP(1)
NAME
gzip, gunzip, zcat - compress or expand files
SYNOPSIS
- gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ... ]
+ 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
+ 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 modi-
fication times. (The default extension 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
+ a file name is "-", the standard input is compressed to the standard
output. Gzip will only attempt to compress regular files. In particu-
lar, it will ignore symbolic links.
If the compressed file name is too long for its file system, gzip trun-
cates 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
+ 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, gzip keeps the original file name and timestamp in the com-
pressed file. These are used when decompressing the file with the -N
- option. This is useful when the compressed file name was truncated or
+ option. This is useful when the compressed 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
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 compressing,
- gzip uses the .tgz extension if necessary instead of truncating a file
- with a .tar extension.
+ 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. gunzip also recognizes the special extensions
+ .tgz and .taz as shorthands for .tar.gz and .tar.Z respectively. When
+ compressing, gzip uses the .tgz extension if necessary instead of trun-
+ cating 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.
+ compress -H or pack. The detection of the input format is automatic.
When using the first two formats, 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
+ 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 complain. This generally means that the
standard uncompress does not check its input, and happily generates
- garbage output. The SCO compress -H format (lzh compression method)
+ garbage output. 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
+ 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 a zip file with a single member, use a command like gunzip
<foo.zip or gunzip -S .zip foo.zip. 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 compress.) zcat
+ zcat is identical to gunzip -c. (On some systems, zcat may be
+ installed as gzcat to preserve the original link to compress.) zcat
uncompresses either a list of files on the command line or its standard
input and writes the uncompressed data on standard output. zcat will
uncompress files that have the correct magic number whether they have a
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 dis-
tribution of common substrings. Typically, text such as source code or
- English is reduced by 60-70%. Compression is generally much better
+ 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).
slightly larger than the original. The worst case expansion 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,
+ of used disk blocks almost never increases. gzip preserves the mode,
ownership and timestamps of files when compressing or decompressing.
The gzip file format is specified in P. Deutsch, GZIP file format spec-
ification version 4.3, <ftp://ftp.isi.edu/in-notes/rfc1952.txt>, Inter-
- net RFC 1952 (May 1996). The zip deflation format is specified in P.
- Deutsch, DEFLATE Compressed Data Format Specification version 1.3,
+ net RFC 1952 (May 1996). The zip deflation format is specified in P.
+ Deutsch, DEFLATE Compressed Data Format Specification version 1.3,
<ftp://ftp.isi.edu/in-notes/rfc1951.txt>, Internet RFC 1951 (May 1996).
OPTIONS
-a --ascii
Ascii text mode: convert end-of-lines using local conventions.
- This option is supported only on some non-Unix systems. For
+ This option is supported only on some non-Unix systems. For
MSDOS, CR LF is converted to LF when compressing, and LF is con-
verted to CR LF when decompressing.
-c --stdout --to-stdout
Write output on standard output; keep original files unchanged.
- If there are several input files, the output consists of a
+ 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
+ compression, concatenate all input files before compressing
them.
-d --decompress --uncompress
-f --force
Force compression or decompression even if the file has multiple
- links or the corresponding file already exists, or if the com-
+ links or the corresponding file already exists, or if the com-
pressed data is read from or written 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 standard output: let zcat behave as cat. If -f is not
+ the standard output: 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.
date & time: time stamp for the uncompressed file
The compression methods currently supported are deflate, com-
- press, lzh (SCO compress -H) and pack. The crc is given as
+ press, 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
+ 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
-N --name
When compressing, always save the original file name and time
stamp; this is the default. When decompressing, restore the
- original file name and time stamp if present. This option is
+ 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.
-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 confu-
- sion when files are transferred to other systems. A null suffix
+ sion when files are transferred to other systems. A null suffix
forces gunzip to try decompression on all given files regard-
less of suffix, as in:
of speed).
ADVANCED USAGE
- Multiple compressed files can be concatenated. In this case, gunzip
+ Multiple compressed files can be concatenated. In this case, gunzip
will extract all members at once. For example:
gzip -c file1 > foo.gz
gzip -cd file.gz | wc -c
- If you wish to create a single archive file with multiple members so
+ 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.
ENVIRONMENT
- The environment variable GZIP can hold a set of default options for
+ 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
The gzip file format is specified in P. Deutsch, GZIP file format spec-
ification version 4.3, <ftp://ftp.isi.edu/in-notes/rfc1952.txt>, Inter-
- net RFC 1952 (May 1996). The zip deflation format is specified in P.
- Deutsch, DEFLATE Compressed Data Format Specification version 1.3,
+ net RFC 1952 (May 1996). The zip deflation format is specified in P.
+ Deutsch, DEFLATE Compressed Data Format Specification version 1.3,
<ftp://ftp.isi.edu/in-notes/rfc1951.txt>, Internet RFC 1951 (May 1996).
DIAGNOSTICS
- Exit status is normally 0; if an error occurs, exit status is 1. If a
+ 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 ...]
memory.
file: already has .gz suffix -- no change
- The file is assumed to be already compressed. Rename the file
+ 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)?
not.
gunzip: corrupt input
- A SIGSEGV violation was detected which usually means that the
+ A SIGSEGV violation was detected which usually means that the
input file has been corrupted.
xx.x% Percentage of the input saved by compression.
ply-linked files.
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
+ 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 gunzip for decompression, gunzip
detects that there is extra trailing garbage after the compressed data
and emits a warning by default. You have to use the --quiet option to
- suppress the warning. This option can be set in the GZIP environment
+ suppress the warning. This option can be set in the GZIP environment
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
+ for reading and writing compressed data on tapes. (This example
assumes you are using the GNU version of tar.)
BUGS
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
+ 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
projects / debian / gzip / blobdiff