- 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, 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.
+ 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).