Getting Started with Linux basics

Linux Terminal type:

/dev/console: Physical Terminal

/dev/tty#: Virtual Terminal

/dev/ttys#: Serial Terminal

/dev/pts/#: Pseudo Terminal

Switching terminals:

CTRL+ALT+F[1-6]: Switch terminal

CTRL+ALT+F1: Switch to the graphical interface

CHVT #: Switch to # # terminal

Init 3: Turn off the graphical interface

Init 5: Start the graphical interface

TTY command: View the type of terminal currently logged in

WHO: See which endpoints are running on the current system

echo $SHELL: Output Current interface program

Cat/etc/shells: View all shells on the current system

Gui:graphic User Interface

Gnone

Kde

Cli:command Line Interface

Bash

Sh

Csh

Ksh

Zsh

...

Command prompt:

[[Email protected]~]# COMMAND

Root: Currently logged in User name

localhost: System host name

~: Current system path

#: User type

#: Super Admin

$: Normal user

Command run Format:

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

short option:-C

long option:--all

CTRL + C to cancel command execution

Multiple commands to run with;

A command can be divided into multiple lines with \

System-related commands:

System shutdown:

poweroff

Halt

Shutdown-h Now

To view the current system version:

lsb_release-a

Cat/etc/centos-release

View current host Name: hostname

View current kernel version: Uname-r

Shell interpreter: Provides an interface between the user and the kernel to convert a user-entered command into a system-aware binary format

Command type:

Internal command: Shell inline command

External command: Executable program file under a path on the current system

To view the command type:

Type COMMAND

View command hash:

Hash

- R: Empty hash Table

- D: Delete the specified hash entry

To disable internal commands:

Enable-n COMMAND

To enable internal commands:

Enable COMMAND

Find the path to the external command:

Which COMMAND

List the path and help documentation for the program

Whereis COMMAND

To define a command alias:

Alias Name= ' COMMAND '

To delete a command alias:

Unalias NAME

Ignore aliases to execute the original command:

/path/to/somefile

\command

' COMMAND '

Command execution Priority:

aliases------> Internal------> Hash------> External commands

Date: Displays the system day and time

System time: Run by the Linux kernel through the CPU's operating frequency

Hardware time: Motherboard

Hwclock,clock: Display hardware time

-S: Synchronize the system time to the hardware, whichever is the hardware time

-W: Synchronizes hardware time to hardware, whichever is the system time

Cal: Show Calendar

Screen: Multiple terminal logins for the same host for shared sessions

To create a new screen session:

screen-s SESSION

Show all screens that are open:

Screen-ls

Join session:

screen-x SESSION

Split session:

ctrl+a,d

To resume a session:

screen-r SESSION

To exit and close the session:

Exit

echo Command: Echo

-N: Do not wrap.

-E: Special handling If the following characters are present, but not as string output

\ t: Insert tab

\a: Warning Sounds

\b: Delete the previous character

\c: Finally, no line break symbol is added

\ n: Wrap and move the cursor to the beginning of the line

\ r: The cursor moves to the beginning of the line, but does not wrap

\ \: Insert \ Character

\0nnn: Inserting ASCII characters with a table in octal

\xhh: Inserting the ASCII characters represented by hexadecimal

echo display with color display, echo display with color, need to use parameter-E

Format: echo-e "\033[word background color; text color m string \033[0m

Word Color: 30-37

Echo-e "\033[30m Black character \033[0m"

Echo-e "\033[31m Red word \033[0m"

Echo-e "\033[32m Green word \033[0m"

Echo-e "\033[33m Yellow word \033[0m"

Echo-e "\033[34m Blue word \033[0m"

Echo-e "\033[35m Purple word \033[0m"

Echo-e "\033[36m sky blue Word \033[0m"

Echo-e "\033[37m White character \033[0m"

Word Background color: 40-47

Echo-e "\033[40;37m Black Bottom White \033[0m"

Echo-e "\033[41;37m Red bottom White \033[0m"

Echo-e "\033[42;37m Green bottom White \033[0m"

Echo-e "\033[43;37m Yellow \033[0m"

Echo-e "\033[44;37m Blue bottom White \033[0m"

Echo-e "\033[45;37m Purple \033[0m"

Echo-e "\033[46;37m sky blue Bottom White \033[0m"

Echo-e "\033[47;30m black character \033[0m on white background"

Control Option Description:

\33[0m Close All Properties

\33[1m Setting High brightness

\33[4m Underline

\33[5m Flashing

\33[7M Reverse Display

\33[8m blanking

\33[30m-\33[37m Setting the foreground color

\33[40m-\33[47m Setting the background color

\33[na the cursor to move n rows

\33[NB cursor down n rows

\33[NC cursor right shifts n rows

\33[nd cursor left n rows

\33[Y;XH Setting the cursor position

\33[2J Clear Screen

\33[k clears the contents from the cursor to the end of the line

\33[s Save Cursor position

\33[u Restore cursor Position

\33[?25l Hide Cursor

\33[?25h Display cursor

To view the colors defined by the Create file:

Cat/etc/dir_colors

"": weak reference, will do variable substitution

": Strong references, all as strings, no variable substitution

' or $ (): command substitution, referencing the execution result of a command

For example:

echo "$VAR": Output values from $var variables

Echo ' $VAR ': Output $var string

Echo ' echo $USER ': output echo $USER command run result

Curly braces expand: {}

Print a simplified form of a repeating string

Touch file{1,3,5}

RM-RF file{1,3,5}

Command completion: Tab key

Bash finds commands from left to right, depending on the path defined in the PATH environment variable

If a user-given string has only one unique command, the direct complement

Otherwise, tab again to the list of commands

Path Completion:

A user-given string that starts with a path and searches for a file at the beginning of a specified string under its specified ancestor directory

If only: the direct complement

Otherwise: Eat tab and give the list

Get help:

Internal Command help:

Help COMMAND

Mans COMMAND

External command help:

COMMAND--help

command-h

Mans COMMAND

Info COMMAND

Whatis: View the function of a command and the chapter in which it resides

Makewhatis: Build Database (CentOS 6)

MANDB: Build Database (CentOS 7)

Getting Started with Linux basics