Introduction to common commands and shortcut keys in Linux

1. Ping
	Format:
    	ping [URL]
 # Determine whether the system can connect to the network normally 2. Host login user information [root@localhost ~]# 
    root: User name for logging into the current system @: separator, no special meaning localhost: Host name of the current system ~: Current directory (~ represents the current home directory, /root)
    #: No actual meaning 3. Customize system login user information PS1 environment variable	
	[root@localhost ~]# echo $PS1
    [\u@\h \W]\$
    [root@localhost ~]# PS1='[\u@\h --- \W]\$'

The usual system command syntax format is:
	command [arguments] [options] [path]

Everything in Linux starts from root (/).

Knowledge reserve:
	cd : change directory

Absolute path: the reference is the root (/) path Relative path: the reference is the current path

1. Shutdown shutdown: Shutdown or restart Parameters: -h: Specify shutdown delay time -c: Cancel shutdown halt: Disable CPU resources poweroff: Turn off the power init: Set system startup mode 0: Shutdown 1: Single user mode 2: Multi-user no network mode 3: Multi-user mode 4: To be determined 5: Desktop mode 6: Restart reboot
		

2. Restart reboot
	init
	shutdown
		parameter:
			-r: Specify the delay time for restart 

Format:
	man [command to view help]
	
		Command explanation information: NAME
		Command syntax description: SYNOPSIS
		Command Description: DESCRIPTION
		Detailed description of command parameters: OPTIONS

	q : Exit /[Search content] : Search content

1. Historical command information: up and down keys 2. Clear screen command: ctrl + l | clear
3. Interrupt and cancel the command execution process: ctrl + c
4. Quickly move the cursor to the beginning and end of the line: ctrl + a/e
5. Cut the information from the cursor to the beginning of the line: ctrl + u
6. Paste the cut content: ctrl + y
7. Cut the information from the cursor to the end of the line: ctrl + k
8. Lock the system window information status: ctrl + s
9. Unlock system window information status: ctrl + q
10. Quickly move the cursor in the command line: ctrl + arrow keys 11. System command information completion function: tab

	1. Display current path information pwd 
	2. Switch directory path information cd 
		Special paths:
			1. -: the path last visited 2. .: represents the current path 3. ..: the previous path 4. ~: home directory Absolute path and relative path 3. Create a directory mkdir
		
		parameter:
			-p: Automatically create parent directories -v: Display the process of creating folders		
		Example: Create a v1 directory in the test directory under the data directory in the previous directory [root@localhost ~]# mkdir -p ../data/test/v1
		
		Note: When mkdir creates a folder, the parent directory of the folder must exist 

	1. Create file information command touch
		[root@localhost ~]# touch 1.txt
	
	2. View data information command ls
		View the file information in the specified directory. By default, the file information in the current directory is viewed.
		parameter:
			-l: Display detailed information of the file -a: Display hidden folders (files or folders starting with . are called hidden folders)
			-h: format file size (must be used with the -l parameter)
			
		[root@localhost ~]# ls -l
        total 4
        -rw-r--r--. 1 root root 0 Dec 9 12:15 1.txt
         -rw-r--r--. : File permissions 1: Number of file hard links root: User root: Group 0: Size (bytes)
         Dec 9 12:15 : created time 1.txt : file name 1B => 8 bytes 1024 bytes = 1kB
         1024kb = 1MB
     
    3. Output print character information echo	
    	Overwrite redirection (>): delete all the contents in the file and then write it Append redirection (>>): write information at the end of the file 4. View file data information cat [path to view the file]