One 、 Complete commands and parameters

Tab key  

Two 、 Terminate the current process

Ctrl+C

3、 ... and 、 Order help

      Commands are divided into internal commands or external commands ,shell（ command interpreter ） The built-in command becomes an internal command , Others are external commands ;
      Command options ： Just enter a command , The content displayed by default can not meet user requirements , Users can add corresponding options , Customize the output ;
      Arguments to the command ： The operation object of the command , Such as ls The summary of is "ls [ Options ] [ file name …]",[ file name ] Namely ls Arguments to the command

1、man command

• man To provide online help , Permissions are all users , Use man Command to access help information

• man command  【 Options ：-C config_file: Specify profile man.conf, The default value is /etc/man.conf】

Input man ls see

stay man In the interface of command help information , The common operation keys included are as follows ：

Key	effect
Space bar ,page down	Turn down a page
page up,b	Page up
home	Go directly to the home page
end	Go directly to the end page
/	Search a keyword from top to bottom , Such as “/linux”
？	Search for a keyword from the bottom up , Such as “？linux"
n	Navigate to the next keyword found
N	Navigate to the last keyword found
q	Exit help document

 man The structure of the help information of the command is as follows ：

Structure name	Representative significance
name	Name of the command
synopsis	General usage of parameters
description	Introduction
examples	demonstration （ With a brief explanation ）
overview	summary
defaults	Default features
options	Specific options available
environment	environment variable
files	Documents used
see  also	Relevant information
history	Maintenance history and contact information

man Several parts of the manual

2、 see bash Internal commands help

The order is bash Built in command , Used for display bash Help information for built-in commands .

help The command can only display bash Help information for built-in commands , For the help information of external commands, you can only use man perhaps info Command view .

help [ Options ] [ Parameters ]

Options

-d： Displays a brief description of the built-in command .

-m： according to man Output help information of built-in commands in the format of manual .

-s： Only output the command format of built-in commands .

Parameters ：bash Built in command ( Can be for more than one , Please separate with a space )

3、help command

4、info page

     info page And man It's used for the same purpose , Are used to query the command usage or file format , But with the man The difference is info page It is to split the file data into paragraphs , Each paragraph is written on its own page , And in each page there are similar pages 【 Hyperlinks 】 To jump to different pages , Each individual page is also called a node （node）

      However, the description file of the target data to be queried must be info Only when it is written in the format of info Special features of （ Like hyperlinks ）. And this support info By default, the file of the command is placed in /user/share/info/ In this directory .

Four 、 View the files in the directory ls（list）

[[email protected] ~]# ls / 
bin boot dev etc home lib lib64 media mnt opt proc root run sbin 
srv sys test tmp usr var 
[[email protected] ~]# ls -dl /root/ 
dr-xr-x---. 2 root root 203 Jun 9 15:30 /root/

5、 ... and 、date command

Input date --help

date Common parameters in commands and their functions ：

Time now ：

6、 ... and 、timedatectl command

• timedatectl The command is used to set the system time , English full name ：“ time date control ”
• The grammar format is ：timedatectl [OPTIONS...] COMMAND ...
• If the computer time is found to be inconsistent with the actual , If it's only a few minutes away , We can directly adjust , But if it's a few hours away , So besides adjusting the current time , It is also necessary to check the time zone .

Input timedatectl --help

• Check the system time and time zone ：timedatectl  status

• If the time zone found is not Shanghai （Asia/Shanghai）, It can be set manually ：

timedatectl  set-timezone Asia/Shanghai 

• If the time is still incorrect , You can manually modify the system date ：

timedatectl  set-time  2022-07-15

• Modification time ：

timedatectl  set-time  14：00

7、 ... and 、file Use of commands

• file The command is mainly used for ： By reading the contents of the document in detail , To identify the type of document
• Command format ：file [OPTION...] [FILE...]
• Exhibition file Type of file ： Input file --help

file Command determines the order of file types :

• Inquire about Device, Directory, Symbolic And so on
• Query compressed files
• Inquire about tar file
• be based on Magic Query of database file
• Inquire about ASCII,UNICODE And other types of text files
• If none of the above meets , Then the file is binary

8、 ... and 、stat Use of commands

1、stat The command is used to display the details of a file or file system ; When displaying file information , Than ls The command is more detailed

2、 Command format ：stat [OPTION]... FILE..

3、 Command options ：-L： Display the information of the file pointed to by the symbolic link ;

                       -f： Displays information about the file system where the file is located ;

                      -t： Output information in a concise way ;

                      -c： Output some information of the file in a specific format

4、 About stat Three times of the file in the command

Access Time： Shorthand for atime, Represents the access time of the file , When file content is accessed , Update this time

Modify Time： Shorthand for mtime, Indicates the modification time of the document content , When the data content of a file is modified , Update this room . 

Change Time： Shorthand for ctime, Indicates the state time of the file , When the state of the file is modified , Update this time , For example, the number of links to a file , size , jurisdiction ,Blocks Count .

Verify through code ：

atime    File access time update

        By using cat Command to view the contents of the file , It is equivalent to accessing the contents of the file , So the access time is updated , The other two times remain the same

mtime    The modification time of the file is updated

adopt echo The command will string 456 Input to file In file , Thus, the contents of the file are modified , therefore mtime change

ctime  The status time of the file is updated

adopt chmod The command changes the permissions of the file , therefore ctime Time changes

Nine 、Linux File types in

Use ls -l The first character you see after the command

1、-    Ordinary documents , Be similar to Windows notepad

2、d  Directory file （directory）, Be similar to Windows Folder

3、c  Character device file （char）, Serial port devices , Sequential reading and writing , keyboard

4、b   Block device file （block）, Interface devices available for storage , Random, speaking, reading and writing , Hard disk

5、p  Pipeline files （pipe）, For interprocess communication

6、s  Socket file （socket）, For communication on the network . You can start a program to listen to the client's request , The client can communicate data through socket .

7、l  Symbolic links are also called soft links , And the original file is not a file （link）, for example Windows Shortcut to , If the original file is deleted , All symbolic links to it are destroyed . Soft links have their own node, yes Linux A kind of special document , As a document , Its data is the path of the file to which it is connected . Symbolic links can span file systems , You can also create a directory .

8、    Hard links , Only files in the same file system can be referenced . It refers to the physical index of the file in the system （ Also known as inode）. When the original file is moved or deleted , Hard links will not be broken , Because it refers to the physical data of the file rather than the location of the file in the structure .