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Linux operating system and commands

GUI: Graphical user interface

Windows

X-windows (CS architecture)

CLI:COMMOMD Line Interface

IDE: The development program that programmers use when they develop a program. (Development environment)

Computer composition

Shell

LIBRARY:API (Library)

Kernel

Hardware

Why do I need a library?

Because of the system call (kernel), fixed on the bottom. So the programmer calls very cumbersome. So the library encapsulates one or more functions into a more advanced application interface. (The library is an executable program, but cannot be run separately)

Kernel

In order to be able to implement on the same computer, the approximate application of multiple programs simultaneously. The kernel is just a platform that does not provide any specific services, but simply abstracts the computing power that the hardware can provide to other software on the upper layer.

Windows

Dll:dynamic link library (dynamic shared libraries)

Linux

So:shared object (Shared object, also known as DSO)

Authentication mechanism: The process of identifying someone. (Password, fingerprint)

↓

Authorization: Authorization

↓

Audit: Audition (log)

Prompt: Command prompt

Why can the program be executed?

Each command has magic numbers (magic number)

list: Lists files under the specified path

directory : path mapping for files

file system : FileSystem

Catalog : Working directory (working directory) current directory (currently directory)

Thinking

is the file name data?

Shortcut key Explanation

- L: long format

File type:-: Normal file (f)

D: Catalog file

B: Block device files (blocks)

C: Character device file (charactor)

L: Symbolic Link files (sumbolic link file)

P: Command pipe (pipe)

S: Socket file (socket)

file permissions, 9-bit, per 3-bit group, rwx (read, write, execute)

Number of hard links to files

Owner of the file

Genus Group of files

File size (size), in units of section

Timestamp (time stamp): Last Modified Time

Access: Access

Modified: Modify, File content changed

Change: change,metadata, meta data

- H Human Readable (unit conversion)

-A displays all with "." Hidden files at the beginning

. Current directory: Upper directory of current directory (parent directory)

- d display the directory's own properties

-I display miniature node (index node Inode)

- r Reverse display file

- R Recursive display

CD: Change directory (switch directory)

Home directories, home directories, home directory

CD ~userneme: Enter the home directory of the specified user (administrator only),

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

Command type

built-in commands (shell built-in)

External command: Under a path in the file system, there is an executable file that corresponds to the command

Type : shows which type the specified command belongs to

Environment variables: named memory space for defining the current user's working environment (attributes, fonts, etc.)

Variable assignment: Name (memory space) =jerry (data)

path: Use a colon to separate a bunch of paths

O (1) Speed: a measure of speed under a hash.

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Rookie Advanced Linux Master Road--fourth day (next)