Linux operating system and common commands

Dll:dynamic Link Library

. so:shared Object

Certification: Authentication

Authorization: Authorization

Audit: Audition (log)

Prompt, command prompt:

Command:

Magic Number: Magic Numbers

Shebang

#！ /bin/bash

• Directory

Directory:: File, Path map

Path: The location that passes from the specified starting point to the destination

Path is the mechanism for implementing hierarchical file management

FileSystem: File System

Inverted tree-like structure

Absolute path, relative path

Working directory working directory, current directory

FHS File System Hierarchy Standard

• ！ Question: Is the file name data?

Ls:list lists, lists

- L: Long format

file Type: the

-: Normal file (f)

D: Catalog file

B: Block device files (blocks)

C: Character device file (character)

L: Symbolic Connection files (sysmbolic link file)

P: Command pipe file (pipe)

S: Socket file (socket)

File permissions: 9-bit, per 3-bit group, each group: rwx

Number of hard links to files

Owner of the file

Genus Group of files

File size (size), in bytes

Time stamp (timestamp) Last modified time

Access: Access

Modified: Modify file content has changed

Change: Change,metadata meta data

-H: Do unit conversions

-A: Displayed with. Hidden files at the beginning

           . Represents the current directory

.. Parent Directory

- D: Display the directory's own properties

-i:index Node,inode Index Node number

-R: Reverse Display

-R: Recursive (Recursive) display

Pwd:printing working Directory

Cd:change Directory

Home directories, home directories, home directory

CD ~username: Enter the home directory of the specified user

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

Command type:

Built-in command (shell built-in), internal, built-in

External command: An executable file with the same name as the command under a path on the file system

• ！ Question: What is a variable?

What is a heap? What is a stack?

Environment variables: named memory space

Variable assignment:

e.g Name=jerry

Path: a bunch of paths that colon splits

O (1): A standard for measuring the speed of a program's execution

The rate at which a data is queried in a list varies depending on the length of the list or is called a function trend.

Type: Shows which type the specified command belongs to

PRINTENV: Display Environment variables

Hash: Key Value Database Cache is King caching enables system acceleration

• Time

Date: Time Management

Linux Time Implementation mode: RTC

Ntp:network Time Protocol

Hardware clock

Software clock

Hwclock

- W: Write system time to hardware

-S: Write hardware time into the system

• Get help with the use of commands

Internal command:

Help COMMAND

External command:

COMMAND--help

Command manual: Manual

Mans COMMAND

Whatis COMMAND

Chapter of Man:

1. User commands (/bin,/usr/bin,/usr/local/bin)---the user Commands

2. System Call---Systems Calls

3. Library User---C library Functions

4. Special files (device files)---Devices and special files

5. File format (configuration file syntax)---file Formats and conventions

6. Game---games et. Al.

7. Miscellaneous---Miscellanea

8. Management commands (/sbin,/usr/sbin,/usr/locacl/sbin)---System administration tools and Deamons

<: Required

[]: Optional

. . . : multiple times can occur

| : Choose one More

{}: Grouping, no special meaning

Mans:

Name: Command name feature brief description

Synopsis: Usage notes, including available options

DESCRIPTION: A detailed description of the command function, including the meaning of each option

Options: Explaining the meaning of each option

Files: The configuration file associated with this command

BUGS:

EXAMPLES: Using the example

See ALSO: Another reference

Flip Screen:

Turn back one screen: SPACE

Turn One screen forward: b

Turn down one line: ENTER

Turn up one line: K

Find:

/keyword forward

N: Next

N: Previous

？ KEYWORD backwards

N: Next

N: Previous

Exit: Q

Online Documentation:

Info COMMAND

• File system

Rootfs: Root file system

Fhs:linux

/boot: System boot related files, such as kernel, INITRD, and Grub (bootloader)

/dev: Device files

Block devices: Random access, data blocks

Character Devices: Linear access, by character bit units (mouse, monitor)

Device number: Main device number (major) and secondary device number (minor)

/etc: Configuration file

Home directory for users, the home directory of each user is usually the default of/home/username

/root: Administrator's home directory

/lib: library file, library file can only be called and cannot be executed separately

Static libraries:. A

Dynamic library:. Dll. So (Shared object)

/lib/modules: Kernel module files

/media: mount point directory, typically used to mount mobile devices

/MNT: Typically used to mount additional temporary file systems

/OPT: Optional Directory

/proc: Pseudo file system, kernel mapping file

/sys: Pseudo file system, property mapping file related to hardware device

/tmp: Temp file,/var/tmp

/var: a variable file

/bin:binary executable file, user command

/sbin: Executables, administration commands

/usr:shared, read-only Global shared read-only file

/usr/bin

/usr/sbin

/usr/lib

/usr/local:

/usr/local/bin

/usr/local/sbin

/usr/local/lib

Naming rules:

1, the length can not exceed 255 characters

2, cannot use/when filename, because/is used when the file delimiter, as well as to represent the root directory of the

3. Strictly case-sensitive

File management, directory management, running programs, device management, software management, process management, network management

• Directory Management

LS, CD, pwd

mkdir: Creating an empty Directory

-p:parent

-v:verbose Show Details

e.g: Command line expansion

Mkdir-pv/mnt/test/{x/m,y}

A_b,a_c,d_b,d_c

{A,d}_{b,c}

# Tree: View directory tree

Rmdir:remove Directory Delete directories, only empty directories can be deleted

- P

• File Management

Touch: Create file, modify file timestamp

-A ,-M,-T,-C

You can also use the file editor to create a file

Stat: Displays status information for a file or file system

ASCII: US standard Information Interchange code

Character translation criteria: Bg18030,gbk,gb2312,unicode

Nano

RM: Deleting files

-I: Default option for administrators to avoid mis-operation

-f:force forcibly deleted

-R: When deleting a directory, the cabinet deletes all of the following files

Cp:copy

E.Q:CP Srcfile DEST

CP file1 File2 File3

CP command only the last one appears is the target

A file to a file

Multiple files to a directory

The CP command copies only files by default and cannot copy directories

- R recursion

-F Force is forcibly copied if the target file has a direct overwrite

-I interactive if present, indicates whether to overwrite

-P Preserve Preserve the owner, group and timestamp of the file

-A archive retains all properties, archive replication, often used for backup

-P Keep the link

-l Copy the file that the link points to

Mv:move for moving files

MV SRC DEST

MV- T DEST SRC

install:copy files and set attributes

- D DIRECTORY

• Summarize:

Catalog management: LS, CD, pwd, mkdir, rmdir, tree

File management: Touch, stat, file, RM, CP, MV, Nano

Date Time: Date Clock hwclock,cal

View text: Cat, TAC, more, less, head, tail

Cat: Connect and display

- n Display line number

-e show ends displays the number of row sections for each row

-A Show All

TAC: Flashback display

CTRL + C

MORE: Turn backwards

Less

Head: View Top N rows

Tail: View after n rows

- N

-F: Look at the end of the file, do not exit, wait to display new content appended to this file

Text Processing:

Cut, join, SED, awk

Database: Databases

Relational database:

Table: two-dimensional table

Text file:

Cut

-D: Specify delimiter, default is space

-F: Specify the fields to display

-F 1,3

-F 1-3

e.g CUT-D:-F1/ETC/PASSWD

Sort: The text is sorted by default in ascending order of characters in the ASCII code table

- N: by numerical size

-r:reverse Reverse

-T: Field delimiter

-K: Which field is the keyword to sort

-U: The same row is displayed only once after sorting

-f:ignore-case ignores character case, adjacent and repeated rows are identified as repeating rows, and interlaced repetition does not count

Uniq:report or omit repeated lines

-d:onely Print Duplicate lines, only duplicate rows are displayed

-d:all-repeated

-c:count shows the number of repetitions of a row

WC: Text Statistics word count

- L: Show only rows

-W: Displays only the number of words

-C: Show only the number of bytes

-M: Displays only the number of characters

-L: Indicates how many characters the longest row contains

TR: character handling, conversion or deletion of characters

TR [OPTION] ... SET1 [SET2]

Linux operating system and common commands