-
-User Commands GZIP(1)
+GZIP(1) GZIP(1)
NAME
- gzip, gunzip, zcat - compress or expand files
+ gzip, gunzip, zcat - compress or expand files
SYNOPSIS
- gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name ... ]
- gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ... ]
- zcat [ -fhLV ] [ 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 (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 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 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.
-
- The gzip file format is specified in P. Deutsch, GZIP file
- format specification version 4.3, <ftp://ftp.isi.edu/in-
- notes/rfc1952.txt>, Internet RFC 1952 (May 1996). The zip
- deflation format is specified in P. Deutsch, DEFLATE Com-
- pressed Data Format Specification version 1.3,
- <ftp://ftp.isi.edu/in-notes/rfc1951.txt>, Internet RFC 1951
- (May 1996).
-
-SunOS 5.8 Last change: local 2
-
-User Commands GZIP(1)
+ 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
+ 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
+ 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
+ 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 compressing,
+ 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, 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 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
+ 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
+ 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
+ .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 dis-
+ tribution of common substrings. Typically, 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 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,
+ 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,
+ <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 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
- 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
-
-SunOS 5.8 Last change: local 3
-
-User Commands GZIP(1)
-
- 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.
-
- 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.
-
- -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.
-
- -q --quiet
- Suppress all warnings.
-
- -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 ).
-
- -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:
-
-SunOS 5.8 Last change: local 4
-
-User Commands GZIP(1)
-
- gunzip -S "" * (*.* for MSDOS)
-
- Previous versions of gzip used the .z suffix. This was
- changed to avoid a conflict with pack(1).
-
- -t --test
- Test. Check the compressed file integrity.
-
- -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).
+ -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 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
+ 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 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
+ 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 for-
+ mat, 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, com-
+ 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
+ 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.
+
+ -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 decompressing, do not restore the
+ original file name if present (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.
+
+ -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
+ useful on systems which have a limit on file name length or when
+ the time stamp has been lost after a file transfer.
+
+ -q --quiet
+ Suppress all warnings.
+
+ -r --recursive
+ Travel the directory structure recursively. If any of the file
+ names specified on the command line are directories, gzip will
+ descend into the directory and compress all the files it finds
+ there (or decompress them in the case of gunzip ).
+
+ -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
+ forces gunzip to try decompression on all given files regard-
+ less of suffix, as in:
+
+ gunzip -S "" * (*.* for MSDOS)
+
+ Previous versions of gzip used the .z suffix. This was changed
+ to avoid a conflict with pack(1).
+
+ -t --test
+ Test. Check the compressed file integrity.
+
+ -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 compression method
+ (less compression) and -9 or --best indicates the slowest com-
+ pression method (best compression). 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
+ Multiple compressed files can be concatenated. In this case, gunzip
+ will extract all members at once. For example:
- gunzip -c foo
+ gzip -c file1 > foo.gz
+ gzip -c file2 >> foo.gz
- is equivalent to
+ Then
- cat file1 file2
+ gunzip -c foo
- 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:
+ is equivalent to
- cat file1 file2 | gzip > foo.gz
+ cat file1 file2
- compresses better than
+ 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:
- gzip -c file1 file2 > foo.gz
+ cat file1 file2 | gzip > foo.gz
- If you want to recompress concatenated files to get better
- compression, do:
+ compresses better than
-SunOS 5.8 Last change: local 5
+ gzip -c file1 file2 > foo.gz
-User Commands GZIP(1)
+ If you want to recompress concatenated files to get better compression,
+ do:
- gzip -cd old.gz | gzip > new.gz
+ 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:
+ 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
+ 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.
+ 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 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.
+ 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 invocation 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)
+ znew(1), zcmp(1), zmore(1), zforce(1), gzexe(1), zip(1), unzip(1), com-
+ press(1), pack(1), compact(1)
- The gzip file format is specified in P. Deutsch, GZIP file
- format specification version 4.3, <ftp://ftp.isi.edu/in-
- notes/rfc1952.txt>, Internet RFC 1952 (May 1996). The zip
- deflation format is specified in P. Deutsch, DEFLATE Com-
- pressed Data Format Specification version 1.3,
- <ftp://ftp.isi.edu/in-notes/rfc1951.txt>, Internet RFC 1951
- (May 1996).
+ 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,
+ <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 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.
+ Exit status is normally 0; if an error occurs, exit status is 1. If a
+ warning occurs, exit status is 2.
- file: Corrupt input. Use zcat to recover some data.
- The compressed file has been damaged. The data up to
+ Usage: gzip [-cdfhlLnNrtvV19] [-S suffix] [file ...]
+ Invalid options were specified on the command line.
-SunOS 5.8 Last change: local 6
+ file: not in gzip format
+ The file specified to gunzip has not been compressed.
-User Commands GZIP(1)
+ 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
- the point of failure can be recovered using
+ zcat file > recover
- 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 machine. Recom-
+ press the file with gzip, which compresses better and uses less
+ memory.
- 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
- 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 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.
- 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.
- 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.)
- 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.
- -- 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.
+ -- 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 multi-
+ ply-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.)
-
-SunOS 5.8 Last change: local 7
-
-User Commands GZIP(1)
+ 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
+ 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
- size:
+ 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
+ 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.
+ 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 compres-
- sion than the default compression level (-6). On some highly
- redundant files, compress compresses better than gzip.
+ In some rare cases, the --best option gives worse compression than the
+ default compression level (-6). On some highly redundant files, com-
+ press compresses better than gzip.
COPYRIGHT NOTICE
- Copyright (C) 1998, 1999, 2001, 2002 Free Software Founda-
- tion, 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.
+ Copyright (C) 1998, 1999, 2001, 2002 Free Software Foundation, Inc.
+ Copyright (C) 1992, 1993 Jean-loup Gailly
- 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 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 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.
+ 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.
-SunOS 5.8 Last change: local 8
+ 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)
projects / gzip / blobdiff