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gzip原理与实现
想在linux下用C实现gzip压缩与解压缩，有没有相关库函数可以调用？
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想在linux下用C实现gzip压缩与解压缩，有没有相关库函数可以调用？
阅读（723） 回复（2）
大家都知道gzip -d 等于gunzip
我看了以下gunzip，发现是到gzip 的连接
可是gunzip 是怎么用gzip实现的？
哪个文件有其实现脚本？
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把某个目录的文件做了一个tar,并用gzip压缩。现在我想把它解开，要选择解压缩的位置则么实现？
如tar文件为all.tar.gz,我想解压缩到/ora03/tst/下。怎么实现？？？默认的是解压到当前目录吗？:(
[ 本帖最后由 AdenHe 于
11:28 编辑 ]
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哪位老大能提供一份关于deflate,gzip,compress这几种压缩和解压算法的C/C++实现代码？
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当前环境：
服务器设备：IBM R6 p550
 操作系统： AIX v5.3
 数据库：DB2 v8.2
 应用服务器：Websphere v5.1
都怎么配置啊！！！！！
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留下联系方式啊
阅读（1110） 回复（3）
到SCO网站下载了gzip安装包安装后,打gzip命令不可用,请各位帮忙?
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因为数据很大，如何使用gzip进行文件的压缩的同时，再（tar）到磁带机上。
又怎样恢复呢？
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下了个 vim的插件，但装的时候出现错误：
$tar xzvf ctags-5.6.tar.gz
gzip: stdin: not in gzip format
tar: Child returned status 1
tar: 由于前面延迟的错误而退出
$file ctags-5.6.tar.gz
ctags-5.6.tar.gz: HTML document text
file了一下，知道该文件不是tar.gz的压缩包，我用firefox却打不开，查了一些资料找不到如何打开！
请问我该如何解开这个包！
谢谢各位！
阅读（10679） 回复（9）
gzip:stdin:not in gzip format
tar:Child returned status1
tar:Error exit delayed from prvious errors
tar vxfz busybox-1.00.tar.bz2后出现以上错误是怎么回事啊？
多谢各位！
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每日一条linux命令（3）
压缩文件大小有两个明显的好处，一是可以减少存储空间，二是通过网络传输文件时，可以减少传输的时间。
gzip是在Linux系统中经常使用的一个对文件进行压缩和解压缩的命令，既方便又好用。
语法：gzip [选项] 压缩（解压缩）的文件名
各选项的含义：
-c 将输出写到标准输出上，并保留原有文件。
-d 将压缩文件解压。
-l 对每个压缩文件，显示下列字段： 压缩文件的大小 未压缩文件的大小 压缩比 未压缩文件的名字
-r 递归式地查找指定目录并压缩其中的所有文件或者是解压缩。
-t 测试，检查压缩文件是否完整。
-v 对每一个压缩和解压的文件，显示文件名和压缩比。
-num 用指定的数字num调整压缩的速度，
-1或--fast表示最快压缩方法（低压缩比），
-9或--best表示最慢压缩方法（高压缩比）。系统缺省值为6。
假设一个目录/home下有文件mm.txt、sort.txt、xx.com。
例1：把/home目录下的每个文件压缩成.gz文件。
$ cd /home
$ ls m.txt.gz sort.txt..gz
例2：把例1中每个压缩的文件解压，并列出详细的信息。
$ gzip -dv *
mm.txt.gz 43.1%-----replaced with mm.txt
sort.txt.gz 43.1%-----replaced with sort.txt
<.gz 43.1%-----replaced
mm.txt sort.
例3：详细显示例1中每个压缩的文件的信息，并不解压。
$ gzip -l *
compressed uncompr. ratio uncompressed_name 277 445 43.1% mm.txt 278 445 43.1% sort.txt 277 445 43.1% xx.com
$ ls mm.txt.gz sort.txt..gz
例4：压缩一个tar备份文件，如usr.tar，此时压缩文件的扩展名为.tar.gz
gzip usr.tar
usr.tar.gz
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(window.slotbydup = window.slotbydup || []).push({
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display: 'inlay-fix'Linux: gzip command
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Ubuntu 14.04 LTS
Linux Commands
Linux: gzip command
This Linux tutorial explains how to use the Linux gzip command with syntax and arguments.
gzip, gunzip, zcat - compress or expand files
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
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 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 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 compressed 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 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 distribution 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 specification version 4.3, &&, Internet RFC 1952 (May
1996). The zip deflation format is specified in P. Deutsch, DEFLATE Compressed Data Format Specification version 1.3, &&,
Internet RFC 1951 (May 1996).
-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.
-c --stdout --to-stdout
Write outpu 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
-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 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.
Display a help screen and quit.
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.
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.
When compressing, always save the original file 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 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 -S &&&*&&&&&&&(*.* for MSDOS)
Previous versions of gzip used the .z suffix. This was changed to avoid a conflict with pack(1).
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 compression 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
&&&&&&gzip -c file2 && foo.gz
&&&&&&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.
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 invocation of the program.
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 machine. Recompress the file with gzip, which compresses 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 do you wish to overwrite (y or n)?
Respond &y& if you want the output &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
it is left unchanged. See ln(1) for more information. Use the -f flag to force compression of multiply-linked files.
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:
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
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