Linux gzip command compression file implementation principle and code examples

gzip is a command often used in Linux systems to compress and decompress files. The new file compressed by this command is usually marked with the extension ".gz".

Let me emphasize again that the gzip command can only be used to compress files, not directories. Even if a directory is specified, only all files in the directory can be compressed.

The basic format of the gzip command is as follows:

[root@localhost ~]# gzip [options] source file

The source file in the command refers to a common file when performing a compression operation, and refers to a compressed file when performing a decompression operation. The commonly used options and their meanings of this command are shown in Table 1.

Table 1 Common options and meanings of the gzip command

【Example 1】Basic compression

The gzip compression command is very simple. You don’t even need to specify the name of the compressed package. You only need to specify the source file name. Let's try it:

[root@localhost ~]# gzip install.log
#Compress instal.log file
[root@localhost ~]# ls
anaconda-ks.cfg install.log.gz install.log.syslog
#The compressed file is generated, but the source file also disappears

【Example 2】Keep source file compression

When you compress a file using the gzip command, the source file disappears, resulting in a compressed file. At this time, some people will have obsessive-compulsive disorder and ask the author: Is it possible to prevent the source file from disappearing when compressing the file? Well, it's possible, but it's awkward.

[root@localhost ~]# gzip -c anaconda-ks.cfg >anaconda-ks.cfg.gz
#Use the -c option, but do not output the compressed data to the screen, but redirect it to the compressed file, so that the file can be compressed without deleting the source file
[root@localhost ~]# ls
anaconda-ks.cfg anaconda-ks.cfg.gz install.log.gz install.log.syslog
#You can see that both the compressed file and the source file exist

【Example 3】 Compress directory

We might take it for granted that the gzip command can compress directories. Let's try it:

[root@localhost ~]# mkdir test
[root@localhost ~]# touch test/test1
[root@localhost ~]# touch test/test2
[root@localhost ~]# touch test/test3 #Create a test directory and create several test files in it
[root@localhost ~]# gzip -r test/
#Compress the directory and no error is reported
[root@localhost ~]# ls
anaconda-ks.cfg anaconda-ks.cfg.gz install.log.gz install.log.syslog test
#But I found that the test directory still exists and has not been converted into a compressed file
[root@localhost ~]# ls test/
test1.gz test2.gz test3.gz
#The original gzip command does not pack the directory, but compresses all the sub-files in the directory separately

In Linux, packaging and compression are handled separately. The gzip command can only compress but not package, so there will be no package directory, and only the files in the directory will be compressed.

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