6.1 Introduction to Compression and Packaging
Common compressed file types in Linux environment:
.zip，.gz，.bz2，.xz，
.tar.gz，.tar.bz2，.tar.xz
The purpose of compression
- Easy file transfer
- Save disk space
- Reduce the time it takes to transfer
- save bandwidth
6.2 gzip compression tool
gzip is the abbreviation of GNUzip, it is a GNU free software file compression program for UNIX system file compression. We often use files with the suffix .gz in Linux, and they are in gzip format.
Note: gzip cannot compress directory files
Syntax: gzip [options] [filename]
options:
-d: decompression (=gunzip)
-num: specify the compression level, where num represents a number from 1 to 9, 9 is the best compression, the default is 6 (The higher the compression level, the higher the CPU consumption)
compression direct compression
[root@cham3 d6z]# find /etc/ -type f -name "*conf" -exec cat {} >> 1.txt \;
[root@cham3 d6z]# du -sh 1.txt 文件压缩前大小
2.2M 1.txt
[root@cham3 d6z]# wc -l 1.txt 查看其内容总行数
34392 1.txt
[root@cham3 d6z]# gzip 1.txt 压缩
[root@cham3 d6z]# ls
1.txt.gz 压缩后，源文件会消失
[root@cham3 d6z]# du -sh 1.txt.gz
336K 1.txt.gz 压缩后文件大小
[root@cham3 d6z]# gzip -d 1.txt.gz 解压文件
[root@cham3 d6z]# du -sh 1.txt
1.3M 1.txt 解缩后文件大小
[root@cham3 d6z]# wc -l 1.txt
34392 1.txt
[root@cham3 d6z]# gzip -1 1.txt 指定压缩级别
[root@cham3 d6z]# du -sh 1.txt.gz
392K 1.txt.gz
[root@cham3 d6z]# gunzip 1.txt.gz
[root@cham3 d6z]# gzip -9 1.txt 指定压缩级别
[root@cham3 d6z]# du -sh 1.txt.gz
336K 1.txt.gz
[root@cham3 d6z]# file 1.txt.gz file 1.txt.gz 查看文件属性
1.txt.gz: gzip compressed data, was "1.txt", from Unix, last modified: Thu Nov 9 10:41:48 2017, max compressionSpecify the compressed directory
[root@cham3 d6z]# gzip -c 1.txt > /tmp/1.txt.gz
[root@cham3 d6z]# ls /tmp/1.txt.gz
/tmp/1.txt.gz
[root@cham3 d6z]# ls 压缩完成后源文件不会消失
1.txt 2.txt.gz
[root@cham3 d6z]# file /tmp/1.txt.gz
/tmp/1.txt.gz: gzip compressed data, was "1.txt", from Unix, last modified: Thu Nov 9 11:12:44 2017Use the zcat command:
[root@cham3 d6z]# zcat 2.txt.gz 可查看压缩文件内部内容decompress
Decompress directly
gzip -d
[root@cham3 d6z]# gzip -d 1.txt.gz 解压文件 解压后文件消失
[root@cham3 d6z]# du -sh 1.txt
1.3M 1.txt 解缩后文件大小
[root@cham3 d6z]# wc -l 1.txt
34392 1.txteg2：gunzip
[root@cham3 d6z]# gunzip 1.txt
[root@cham3 d6z]# ls
1.txt 2.txt.gz
6.3 bzip2 compression tool
bzip2 is a lossless compression software based on Burrows-Wheeler transform, the compression effect is better than the traditional LZ77/LZ78 compression algorithm. It is a free software. It can be freely distributed and used for free. It is widely present in many distributions of UNIX & LINUX. bzip2 enables high-quality data compression. It utilizes advanced compression technology and can compress ordinary data files by 10% to 15%. The compression speed and decompression efficiency are very high! Supports most compression formats, including tar, gzip and so on.
Note: bzip2 cannot compress directory files
Syntax: bzip2 [options] [filename]
options:
-d: decompress
-z: compress (=bzip2, so it can be used directly without this parameter)
If not installed, please install it first
[root@cham002 dabao]# yum -y install bzip2-x86_64
已加载插件：fastestmirror
The usage of bzip2 is the same as gzip.
compression
[root@cham3 d6z]# bzip2 1.txt
[root@cham3 d6z]# ls
1.txt.bz2 2.txt.gz
[root@cham3 d6z]# du -sh 1.txt.bz2
172K 1.txt.bz2 较gzip压缩程度更高
decompress
[root@cham3 d6z]# bzip2 -d 1.txt.bz2
[root@cham3 d6z]# ls
1.txt 2.txt.gz
[root@cham3 d6z]# du -sh *.txt
1.3M 1.txt
1.3M 2.txt
——————————————————————————————————————————————————————
[root@cham3 d6z]# bzip2 -z 1.txt
[root@cham3 d6z]# ls
1.txt.bz2 2.txt
[root@cham3 d6z]# bunzip2 1.txt.bz2 方法2
[root@cham3 d6z]# ls
1.txt 2.txt
[root@cham3 d6z]# !du
du -sh *.txt
1.3M 1.txt
1.3M 2.txtDescription: Same as gzip, this command can also specify a directory for compression and decompression.
case
Scenario: When viewing a directory file, there is a file 1.txt in it, and the following prompt appears when viewing its content with commands such as cat: "1.txt" may be a binary file. See it anyway? . Press 'y' at this time, a bunch of garbled characters will appear on the screen, quickly press q to exit, and then find the reason: use the file command!
[root@cham3 d6z]# ls
1.txt 2.txt.gz 3.txt
[root@cham3 d6z]# less 1.txt
"1.txt" may be a binary file. See it anyway?
[root@cham3 d6z]# file 1.txt
1.txt: bzip2 compressed data, block size = 900k
After viewing the file information by the file command, it is known that it is a '.bz2' compressed file, that is, you can use the bzcat command to view it, and change its file name to the correct format to prevent it from being misled again.
[root@cham3 d6z]# bzcat 1.txt
由于内容太多，在此不做演示
[root@cham3 d6z]# mv 1.txt 1.txt.bz26.4 xz compression tool
xz is a compressed file format, which is compressed by LZMA SDK, and the target file is 30% smaller than gzip compressed file (.gz or tgz) and 15% smaller than bz2.
Note: xz cannot be used to compress directory files
Syntax: xz [options] [filename]
options:
-d: The decompression
method is the same as gzip and bzip2, and the compression degree is higher.
compression
[root@cham3 d6z]# xz 1.txt
[root@cham3 d6z]# du -sh 1.txt.xz
40K 1.txt.xz
[root@cham3 d6z]# file 1.txt.xz 查看压缩文件类型
1.txt.xz: XZ compressed data
[root@cham3 d6z]#xzcat 2.txt.xz 查看压缩文件内容 “内容过多不复制”decompress
[root@cham3 d6z]# xz -d 1.txt.xz
[root@cham3 d6z]# ls
1.txt 2.txt.gz 3.txt
[root@cham3 d6z]# du -sh 1.txt
2.0M 1.txt
————————————————————————————————————————————————————————
[root@cham3 d6z]# unxz 1.txt.xz
[root@cham3 d6z]# ls
1.txt 2.txt.gz 3.txt
Like gzip and bzip2, this command can also specify a directory for compression and decompression.
[root@cham3 d6z]# xz -c 1.txt > /tmp/1.txt.xz
[root@cham3 d6z]# ls /tmp/1.txt.
1.txt.bz2 1.txt.gz 1.txt.xz
[root@cham3 d6z]# ls /tmp/1.txt.xz
/tmp/1.txt.xz
[root@cham3 d6z]# xz -d -c /tmp/1.txt.xz > ./4.txt
[root@cham3 d6z]# ls
1.txt 2.txt.gz 3.txt 4.txt