Linux Basic Concepts (1)

Linux Basic Concepts

Terminal equipment is divided into three kinds: physical terminal, virtual terminal, analog terminal.

Physical Terminal: A monitor and keyboard device that connects directly to the host.

Device file path:/dev/console

Virtual Terminal: A terminal that is attached to the physical terminal as a virtual implementation in software form. A graphical terminal is also included in the virtual terminal.

Graphical Terminal: A terminal that is attached to a virtual terminal in the form of software to provide a desktop environment. Device file path:/dev/tty#

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Analog Terminal: a command window opened in the graphical interface, using SSH or a telent remote connection open Interface

Device file path:/dev/pts/#

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The terminal is the device that the user interacts with the host and must use.

View current terminal devices: TTY

Interactive interface: After starting the terminal, attaching an interaction on the end device is the application

The interactive interface is divided into two types: 1,gui: Graphical user interface

2,CLI: Text interface (character interface)

[[email protected]~]#, divided into two parts.]

1, [[email protected]~]:P S1

2, the command prompt (prompt) is divided into two types, namely #, $

1) #, run as Administrator.

2) $, run in normal user mode.

Show all shells under the current system:

At the command prompt (#) Cat/etc/shells

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This diagram shows that all sh, bash, nologin, Dash, tcsh, csh are present in the system.

Displays the currently used shell:

At the command prompt (#), Echo ${shell}

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This figure shows that the shell used before is bash.

Run command: Draw the shell program to find the executable program or code corresponding to the typed command and parse it and submit a kernel allocation resource to run it: it behaves as one or more processes.

There are two types of commands that can be executed in the shell: 1. Built-in Commands 2. External commands

1. Built-in command: The shell comes with, and is provided in a command form. Internal commands are executed very quickly. This is because no other process has been created because of the execution of this command.

2. External command: In the current system of a file system path has a corresponding executable program file: You can use the which, Whereis command to view the path.

Distinguish internal or external commands: #type

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To run the command:

Command format:

COMMAND [OPTIONS ...] [ARGUMENTS ...]

Command: Commands

Options: Option

ARGUMENTS: Parameters

Options: 1. Some features to enable or disable commands.

2. Options are divided into long options and short options.

Short options:-one character (c) For example-l,-h

Multiple short options can be combined using: For example-l–h, can be written as-lh

Long options:--a word (word) such as-long,--human-readable

Parameters: The object of the command, providing data to the command:

The command itself is written on the leftmost side, and the command itself is an executable binary program or

Built-in commands from the shell.

Attention:

1. Multi-option and multi-parameter and command should be separated with white space characters

2. Cancel command execution: Ctrl + C

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Linux Basic Concepts (1)