User Interface

Graphical User Interface

Graphical User Interface (GUI) commonly referred as the User Interface (UI).

Command Line Interface

Command Line Interface (CLI) facilitates the users to perform powerful operations on a computer with simple commands.
Command is a text instruction to a computer program to perform a specific task.

What is Shell?

Shell is the software that interprets and executes the various commands that we provide.
Terminal is a text input/output environment.

Different Shells

Bourne Shell (sh)
Bourne-Again Shell (bash)
C Shell (csh)
Korn Shell (ksh)
Z Shell (zsh)

Opening Terminal

Bash is one of the most commonly used shell in Linux distributions.

Open the Dash (Super Key) or Applications and type terminal.
Shortcut: Ctrl + Alt + T

Opening Terminal (in MAC)

Open Launchpad and search for terminal.
Press command(⌘) + space, type "terminal".

For Windows Operating System

For windows install WSL2 (Windows Subsystem for Linux).

Note

Note: It is suggested to try the commands taught bash. As they will not work in Windows Powershell & Command Prompt.

Opening WSL2 Ubuntu Terminal

Click Start and search for "Ubuntu".

Using Cloud

Alternatively you can use Google Cloud Shell.

https://shell.cloud.google.com/

Bash

Commands

Listing Files & Directories

is used to list files and directories.

1
ls

Using Additional Options

-l -h option provides details in human readable format.

Some options require values arguments/values to be passed.
- --block-size option rounds the file size to nearest values.
- Inputs : KB , MB

Get Options for Commands

help

displays a list of options that you can use with the command.

1
ls --help

This Command will be helpful when you don’t know about its parameters and return type etc.

Clear the Screen

clear
command clears the terminal.
Shortcut:
Ctrl+L
.

1
clear

Get User Manual for Commands

man
displays the user manual of a command .
Here we pass the command as an argument.

Syntax:

1
man <command>

Example:

1
man ls

Type q to exit the manual

Get System Date & Time

date

displays the system date and time.

1
date

Get Current User

whoami

displays the current logged in user.

1
whoami

Previous Commands

Shell keeps track of the commands you have typed in.
Use up ( ⬆) and down ( ⬇) arrows to access the commands.

History

history
display the history of the commands you have typed in so far.
By default, It shows the last 500 recent commands.

1
history

Bash History

Bash maintains the history to . bash_history file.

1
cat .bash_history

exit

to close/end a shell session.

1
exit

Summary

Command	Description
ls	List files & directories
date	Displays the system date and time
whoami	Displays current logged in user
--help	Displays list of options for a given command
man	Displays user manual for a given command
clear	Clears the shell
history	It will show you the last five hundred commands you have entered.
exit	Ends the shell

Getting Started with Command Line