3rd Linux Common Commands (4) _ Help, user management and decompression commands

4. Help Commands

4.1 Get help info: man

(1) Man command

Command name	Man (English literal: manual)
Command path	Usr/bin/man
Execute permissions	All Users
Grammar	man [level] [command or configuration file] [Space] or PGDN: Page Down PgUp: Page Up [Enter] or DOWN ARROW: line break Q or Q: Exit In the bottom left, Enter/To find content, and then press N to continue looking.

(2) Precautions

Several levels of the ①man manual

Level	Representative content
1	Shell command or executable file
2	System APIs provided by kernel
3	Common functions and libraries (mostly C libraries)
4	Description of the device documentation, usually in/dev files
5	View the configuration file or file format
6	See the game's help
7	Miscellaneous (including network protocol, ASCII code and other instructions
8	Administrative instructions available to system administrators
9	Files related to Kernel

　　② whatis [command name] or apropros [profile name] is available when viewing brief information about a command

(3) Application examples:

① help information for the LS command: #man ls

② View the Help information for profile services: $man Services (note that you only need to configure the file name, no absolute path is required/etc/services)

4.2 get help with Shell built-in commands:

(1) Help command

Command name	Help
Command path	Shell built-in commands
Execute permissions	All Users
Grammar	Help command

(2) Application examples

① to view Help for the umask command: $help umask

5. User Management commands

5.1 Add New User: Useradd

(1) Useradd command

Command name	Useradd
Command path	Usr/bin/useradd
Execute permissions	Root
Grammar	Useradd User Name

(2) Application example: #useradd user1

5.2 Set User password: passwd

(1) passwd command

Command name	passwd
Command path	usr/bin/passwd
Execute permissions	All Users
Grammar	passwd User Name

(2) Application examples:

$PASSWD User1//re-enter the old password and the new password, but the password required for normal user permissions to change is complex enough.

5.3 view logged in user information: Who

(1) Who order

Command name	W.H.O.
Command path	Usr/bin/who
Execute permissions	All Users
Grammar	W.H.O.

(2) Application examples:

① view currently logged on User: #who (where TTY indicates local terminal login, PTS indicates remote terminal logon)

5.4 view logged in User details: w

(1) W command

Command name	W
Command path	usr/bin/w
Execute permissions	All Users
Grammar	W

(2) Application examples:

① View details of the currently logged on user: #w

6. compression and decompression commands

6.1 compress, unzip files: Gzip/gunzip

(1) Gzip/gunzip command

Command name	Gzip/gunzip (English original: GNU zip/unzip)
Command path	/bin/gzip (Gunzip)
Execute permissions	All Users
Grammar	gzip [file] -C writes the output to the standard output and retains the original file -D Unzip the compressed file gunzip [Compressed file]
File format after compression	. gz

(2) Precautions

　　①gzip can only compress files, not directories

② by default, the original file will not be preserved after compression

③gzip command has 60%~70% compression rate for text files

(3) Application examples

① compressed file: #gzip testfile//Compressed file name is testfile.gz

② keep the original file compression: #gzip-C a.txt

① Decompression: #gunzip testfile.gz

6.2 Package catalog file: Tar

(1) Tar command

Command name	Tar
Command path	/bin/tar
Execute permissions	All Users
Grammar	tar [-ZCXF] [file name after compression] [table of contents] - C : Packaging - x : Unpacking -V: Show more information - F : Specify the file name - Z : Unzip when package is compressed/uncompressed at the same time
File format after compression	. Tar or. tar.gz

(2) Application examples

① packaging and compressing the test catalog two methods

Method 1 (two steps):

#tar –CVF test. Tar // - f means the specified compressed file name is Test.tar # gzip test. Tar

Method 2: (only 1 steps)

#tar –zcf test. tar. GZ test

② decompression: #tar –zxvf test.tar.gz

6.3 compress, extract files or directories: Zip/unzip

(1) Zip/unzip command

Command name	Zip/unzip
Command path	/usr/bin/zip (Unzip)
Execute permissions	All Users
Grammar	Zip [-r] [filename compressed] [file or directory] - R : Compressed Directory Unzip [ compressed file]
File format after compression	. zip

(2) Precautions

① can compress files or directories

② The original file is still retained after the command is executed

(3) Application examples

① compressed Files: #zip testfile.zip test

② Compressed directory: #zip –r testdir.zip TestDir

③ Decompression: #unzip testdir.zip

6.4 compressed Files: bzip2b/bunzip2

(1) BZIP2/BUNZIP2 command

Command name	Bzip2
Command path	/USR/BIN/BZIP2 (BUNZIP2)
Execute permissions	All Users
Grammar	bzip2 [-K] [file] - k : Preserve original file (keep) after generating compressed file BUNZIP2 [-K] [compressed file] - k : Retain original file (keep) after decompression
File format after compression	. bz2

(2) Precautions

① can only compress files and cannot compress directories

　② The original file is not preserved after the command is executed by default . If you want to keep the original file, you can add the-k option

(3) Application examples

① Compressed Files: #bzip2-K testfile

② compressed file: #tar –jcf testfile.tar.bz2//-j means compressed into. bz2 format

③ decompression: #bunzip –k testfile.tar.bz2

④ Unzip file: #tar –jxf testfile.tar.bz2

3rd Linux Common Commands (4) _ Help, user management and decompression commands