Rookie Learn Linux NO. 003 notes Linux operating system and common commands 1

Certification: Authentication

Authorization: Authorization

Audit: Audition (log logs)

Magic Number: Magic Numbers

Pwd:print working directory displays the current path

List:ls used to list the current directory or the file under the specified directory by default display the current directory

Option-L Displays file properties

File properties

The meaning of the characters displayed in the 1th digit

-: Normal file

D: Catalog file

B: Block device files (blocks)

C: Character device file (character)

L: Symbolic Link files (symbolic link file)

P: Named pipes (pipe)

S: Socket file (socket)

Next 9-bit file permissions: Three groups (owner group other), each group of rwx (read write execution excution)-no this permission

Number of hard links to the next file

Owner of the file

Genus Group of files

File size (size), in bytes

Time stamp (timestamp) shows the last time that was modified here

File has three timestamps

Access: Access

Modification: Modify modification means changing the contents of a file

Changing: Change metadata metadata changes the properties of a modified file

Filename

-H Human unit conversion for easy viewing of file sizes

-A shows hidden files starting with.

-D Display the directory itself property

-I index node number

-R Reverse Display file

-R Recursive (recursive) display

cd command (change directory)

Used to switch the working directory, CD without any options and parameters, back to home directories, home directory

CD ~username into the specified user's home directory (only administrators can use it)

CD-: Switch between the current directory and the previous directory

Command type:

Built-in command (shell built-in) a shell builtin is the shell built-in

External command: There is an executable file corresponding to the command name in a path on the file system

Type: shows what kind of command the commands belong to

Environment variables: Used to define the current user's configuration

Printenv This command is used to view the user's environment variables

Path: Multiple paths separated by colons, the first time a user executes a command without a path, actually a shell program from the path specified by the first to find out if there is a command entered by the user,

If not found, the command entered by the user cannot be executed. If found, then execute.

and put the command into the cache hash, when the user executes the command for the second time, the program will go to the hash to find, the speed will be very fast.

Hash cache records previously used command history

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Rookie Learn Linux NO. 003 notes Linux operating system and common commands 1