Basic commands for CentOS

Basic commands for CentOS

Common basic commands:

Type COMMAND: displays the type of the specified COMMAND.

Whatis COMMAND: View COMMAND summary and Chapter Information

Info COMMAND: online document

Hwclock-w: synchronize system time to hardware time

Hwclock-s: Synchronize hardware time to system time

Touch: file timestamp modification command

Touch-c file: Modify the timestamp. If the file does not exist, it is not created.

Touch-a file: only modify the access time

Touch-m file: only modify the modification time

Touch-m-t TIME file: Specifies the modification TIME

Stat file: view the file Timestamp

Install: You can create directories, copy files and folders like the cp command, and get more man install

Hash: View command Cache

History: displays historical commands.

-C: Clear history commands

-D offset [n]: Command to delete a specified position

-W: Save the history command to the history file [./bash_history]

Tips for using History commands:

! [N]: The Nth command in the execution history command

! -N: Execute the nth command in the History command

!! : Execute the previous command

! String: the most recent command in the History command that starts with a specified string.

! $: Reference the last parameter of the previous command

Esc,.: reference the last parameter of the previous command

File Management commands:

Cat: connect and display

-N: displays the row number.

-E: displays the row Terminator.

-A: equal to-vET

Tac: Display from the last line up

More and less: split-screen display

Head-n ROW: view the first N rows of the file

Tail-n ROW: N rows after the file is viewed

-F: Check the end Of the file. Do not exit. Wait until new content is added to this file.

Cut: format text output

-D: Specifies the field separator. The default value is space.

-F: Specifies the displayed field.

Diffuse representation:

-F: displays the first and third fields.

-F 1-3: display the first to third Fields

Sort: Text sorting

-N: sort by value

-R: sort in descending order

-T: Specifies the field separator.

-K: specify a field as a keyword for sorting.

-U: deletes duplicate rows after sorting.

-F: case-insensitive characters are ignored during sorting.

Note: Only adjacent and identical rows are duplicate rows. Otherwise, non-adjacent rows are not duplicate rows.

Uniq: Text sorting

-D: only duplicate rows are displayed.

-C: displays the number of repeated rows in the file.

Wc: Text statistics

-L: displays only the number of rows.

-W: only display the number of words

-C: only display the number of bytes

-M: only the number of characters is displayed.

-L: the maximum number of characters in a row

Tr: Convert or delete characters

Format: tr [OPTION]... SET1 [SET2]

-D: Delete All characters in the character set.

User management commands:

Useradd [options] USERNAME: create a user

-U: Specify UID

-G: Specify the GID

-G: additional group GID ,...

-C: "COMMENT"

-D: Specifies the home directory.

-S: Specifies the SHELL

-M: do not create a home directory

-R: Add a system user

Userdel [option] USERNAME: delete a user

-R: Delete the home directory at the same time.

Id [option] USERNAME: view User Account attributes

-U,-g,-G,-n

Finger USERNAME: view User Account Information

Usermod [option] USERNAME: Modify user account attributes

-U: UID

-G: GID

-A-G: GID (if the-a option is not used, the previous additional group will be overwritten)

-C: "COMMENT"

-D-m: Specify the new home directory and move all files in the old home directory to the new home directory.

-S: Modify the User SHELL

-L: Modify the user's login name

-E: Specifies the user's expiration time.

-L: locked the account

-U: Unlock the account

Passwd [USERNAME]: Password Management

-- Stdin: Read Password from standard input

-L: the user account is locked.

-U: Unlock the user account

-D: Delete the user password.

Pwck: Check User Account Integrity

Groupadd: Creates a group.

-G: Specify the GID

-R: Add a system group

Groupdel: deletes a group.

Gpasswd: Add group password

Permission management commands:

Chown: Modify the owner and group

Chown USERNAME file ,...

Chgrp GROUPNAME file ,...

Chown USERNAME: GROUPNAME file

-R: recursively modifies directories and their internal file owners and groups.

Chmod xxx: Modify file permissions

-R: recursively modify the Directory and its internal File Permissions

File search commands:

Locate:

Non-real-time, fuzzy match, search based on the entire system file database;

# Updatedb: manually generate a file database;

Find:

Real-time;

Accurate;

Supports multiple search criteria;

Traversing all files in the specified directory to complete the search is slow;

Format: find "Search Path" "Search standard" "find future processing actions"

Search Path: the current directory by default;

Search criteria: All files in the specified path by default;

Action: display to the screen by default;

Matching criteria:

-Name 'filename': exact match of file names

Wildcard File Name:

*: Any character of any length

?

[]

-Iname 'filename': the file name is case insensitive when matching.

-Regex PATTERN: Name matching based on regular expressions

-User USERNAME: search by owner

-Group GROUPNAME: search by group

-Uid UID: search by UID

-Gid GID: search by GID

-Nouser: Search for files with no owner

-Nogroup: Search for files without groups

-Type: search by file type

F: Common File

D: Directory

C: character device

B: Fast Device

L: Link file

P: MPS queue Device

S: Socket Device

-Size [+ |-]: search by file size

[+ |-] # K

[+ |-] # M

[+ |-] # G

+: Greater

-: Less

Combination conditions:

-A: corresponds

-O: or

-Not: non

-Mtime: modification time

-Ctime: Change Time

-Atime: Access time

[+ |-] #

+: At least # days have not been accessed (# days ago)

-: I have visited the website within the last # days (# Within the day)

-Perm mode

-Mode: exact match (exact match)

/Mode: any matching condition is met.

Action:

-Print: Display

-Ls: similar to ls-l

-OK COMMAND \;: the user must confirm each operation.

-Exec COMMAND \;: user confirmation not required