Terminal (Command Line) Basics

Terminal Basics - Command Line Introduction
📖 Reading Time: ~10 min 🎯 Level: Beginner

When you hear "terminal" or "command line," do you think of it as a difficult black screen where you type text? Actually, the terminal is the most important and very convenient tool for using Linux once you get used to it. This article explains from basics to practice in beginner-friendly terms.

📋 Table of Contents

  1. What is a Terminal?
  2. Why Use a Terminal?
  3. Difference Between GUI and CUI
  4. About Shell
  5. Terminal Structure and How to Read It
  6. Basic Operations and Shortcuts
  7. Basic Command Structure
  8. Common Mistakes and Solutions
  9. Next Steps

1. What is a Terminal?

💻 In Simple Terms

A terminal is an application for sending text commands to your computer. Also called the command line, you operate your computer by typing commands (instructions) with your keyboard.

🎭 Let's Understand with an Analogy

🍽️ Ordering at a Restaurant...

🖱️ GUI (Mouse Operation)

Point at menu to order
"I'll have that dish" - pointing at a picture

⌨️ CUI (Terminal)

Order verbally with exact dish name
"Pescatore, large size, with extra cheese" - specific details

🔧 Technical Definition

Technically, a terminal consists of the following elements:

  • Terminal Emulator: Screen application that displays text
  • Shell: Program that interprets and executes commands
  • Command Line Interface (CLI): Text-based operation method

💡 What a Terminal Looks Like

yamada@penguin-gym:~$ ls -la
total 24
drwxr-xr-x 2 yamada yamada 4096 Sep 14 10:30 .
drwxr-xr-x 3 root     root     4096 Sep 14 10:25 ..
-rw-r--r-- 1 yamada yamada  220 Sep 14 10:25 .bash_logout
-rw-r--r-- 1 yamada yamada 3771 Sep 14 10:25 .bashrc
-rw-r--r-- 1 yamada yamada  807 Sep 14 10:25 .profile

This is an actual terminal screen. Text is displayed on a black (or white) background, and you enter and execute commands.

2. Why Use a Terminal?

You might think, "Why bother typing text commands when clicking with a mouse is easy?" Actually, the terminal has many advantages that GUI doesn't have.

⚡ Speed and Efficiency

🖱️ GUI (Mouse Operation)

  1. Open file manager
  2. Click and navigate to target folder
  3. Open right-click menu
  4. Select "New Folder"
  5. Enter folder name
  6. Press Enter key

⏱️ Time required: ~10-15 seconds

⌨️ Terminal

mkdir new-folder

⏱️ Time required: ~2-3 seconds

🔄 Automation and Repetitive Processing

Example: Renaming 100 files

🖱️ GUI

Right-click → Rename → Type 100 times
⏱️ ~30-60 minutes

⌨️ Terminal
for i in {1..100}; do mv "file$i.txt" "new_file$i.txt"; done

⏱️ ~1-2 seconds

🎯 Precise Control

  • Option Specification: Can specify detailed settings precisely
  • Pipe Processing: Combine multiple commands for sequential execution
  • Conditional Branching: Can do "if...then..." processing
  • Log Recording: Automatically save history of executed operations

💼 Professional Necessity

Essential Skill in IT Industry

  • Server Management: Many servers don't have GUI
  • Programming: Development environment setup and management
  • Data Analysis: Efficient processing of large datasets
  • DevOps: Automation and continuous integration

3. Difference Between GUI and CUI

🎨 GUI (Graphical User Interface)

Characteristics

  • Visual: Operate with icons, windows, and menus
  • Intuitive: Easy to understand what to do visually
  • Mouse-focused: Centered on click and drag operations

Advantages

  • Easy to understand for beginners
  • Visual feedback available
  • Less prone to mistakes

Disadvantages

  • Repetitive tasks are inefficient
  • Difficult to control precisely
  • High resource consumption

📝 CUI (Character User Interface)

Characteristics

  • Text-based: Operate with text commands
  • Accuracy-focused: Enter specific instructions as text
  • Keyboard-focused: Centered on typing

Advantages

  • Fast and efficient operation
  • Easy to automate and script
  • Low resource consumption
  • Precise control possible

Disadvantages

  • High learning cost
  • Need to memorize commands
  • Typos easily cause errors

🎯 Which Should You Use?

Choosing the right tool for the task is important:

  • GUI: Image editing, video viewing, document creation, etc.
  • CUI: File management, system settings, programming, etc.

Professional engineers use both appropriately for the right situation.

4. About Shell

The shell is a program that mediates between the user and the Linux kernel (OS core). It understands the commands you enter and executes them appropriately.

🐚 Shell's Role

1. Receive Command

Receives command input from user

2. Interpret & Parse

Understands command meaning and converts to executable form

3. Execute

Sends command to Linux kernel for execution

4. Display Results

Shows execution results to user in understandable format

🔧 Main Shell Types

🔵 Bash (Bourne Again Shell)

The most common shell. Standard on most Linux distributions.

Default Rich Features Beginner-Friendly

⚡ Zsh (Z Shell)

High-powered shell extending Bash functionality. Excellent auto-completion and theming features.

Feature-Rich Highly Customizable macOS Default

🐟 Fish (Friendly Interactive Shell)

Modern shell focused on usability. Features real-time completion.

Beginner-Friendly Real-time Completion Modern

💡 How to Check Current Shell

echo $SHELL
# Example result: /bin/bash

This command checks which shell you're currently using.

5. Terminal Structure and How to Read It

The text string displayed when you open a terminal contains important information. Understanding each element helps you accurately grasp the current situation.

🔍 Prompt Structure

yamada@penguin-gym:~/Documents$ _
yamada 👤 Username
@ 🔗 Separator
penguin-gym 💻 Computer name (hostname)
: 🔗 Separator
~/Documents 📂 Current location (directory)
$ ⚡ Prompt symbol (regular user)

🔍 Meaning of Prompt Symbols

$ (Dollar Sign)

Indicates you're logged in as a regular user. This is displayed during normal operations.

# (Hash Sign)

Indicates you're logged in as administrator (root). You have permission to change important system settings.

⚠️ Caution: Root privileges are too powerful, so avoid using them except when necessary.

📂 Understanding Path Notation

Absolute Path vs Relative Path

🗺️ Absolute Path

Complete path starting from root directory (/)

/home/yamada/Documents/report.txt
📍 Relative Path

Path from current location

./Documents/report.txt ../Desktop/image.png

🏠 Special Directory Symbols

~

Home directory
(/home/username)

.

Current directory

..

Parent directory
(one level up)

/

Root directory
(top level)

6. Basic Operations and Shortcuts

To use the terminal efficiently, it's important to learn basic operation methods and shortcut keys.

⌨️ Basic Key Operations

📝 Text Input & Editing

Enter

Execute command

Backspace

Delete one character (left)

Delete

Delete one character (right)

Tab

Auto-completion

🔄 History Operations

↑

Previous command

↓

Next command

Ctrl + R

History search

history

Display history list

🚀 Useful Shortcut Keys

⚡ Cursor Movement

Ctrl + A Move to beginning of line
Ctrl + E Move to end of line
Ctrl + ←/→ Move by word

✂️ Text Operations

Ctrl + U Delete from cursor to beginning of line
Ctrl + K Delete from cursor to end of line
Ctrl + W Delete previous word

🛑 Process Control

Ctrl + C Force stop running command
Ctrl + Z Pause process
Ctrl + D Exit terminal (logout)

🎯 Tab Completion Feature

Tab completion is one of the terminal's most powerful features. Pressing Tab mid-input automatically displays and completes possible candidates.

💡 Tab Completion Example

Input:

cd Doc[Tab]

Result:

cd Documents/

Type "Doc" and press Tab to auto-complete to "Documents".

7. Basic Command Structure

Linux commands have a defined structure. Understanding this structure makes new commands easier to understand.

🏗️ Basic Structure

ls -la /home/user
ls 🔧 Command Name

Specifies process to execute

-la ⚙️ Options

Detailed command settings

/home/user 📂 Arguments

Target files or directories for processing

🔧 Option Types

🔤 Short Form Options

One hyphen + one letter

ls -l -a -h

Multiple options can be combined:

ls -lah

📝 Long Form Options

Two hyphens + word

ls --list --all --human-readable

High readability, easy to understand what the option does

📋 Argument Types

📁 File/Directory Arguments

cat file.txt cd /home/user/Documents

📝 String Arguments

echo "Hello World" grep "error" logfile.txt

🔢 Numeric Arguments

head -10 file.txt chmod 755 script.sh

💡 Command Combinations

🔗 Pipe (|)

Pass output of previous command as input to next command

ls -l | grep ".txt"

Show only lines containing ".txt" from "ls -l" results

🔀 Redirect (>, >>)

Save command output to a file

ls -l > filelist.txt

Save "ls -l" results to filelist.txt file

8. Common Mistakes and Solutions

Here are common mistakes terminal beginners often make and how to fix them.

🚫 Common Mistakes

❌ Command Not Found

bash: command not found: lst
🔧 Cause and Solution
  • Typo: Fix "lst" → "ls"
  • Command not installed: Install if needed
  • Path not set: Specify full path or set path

❌ No Permission

Permission denied
🔧 Solutions
  • Use sudo: sudo command
  • Change permissions: chmod +x filename
  • Check owner: ls -l filename

❌ File or Directory Not Found

No such file or directory
🔧 Solutions
  • Check path: pwd to confirm current location
  • Confirm file existence: ls to display file list
  • Use absolute path: Specify complete path

🛟 What to Do When in Trouble

📖 man Command

Display detailed command manual

man ls

Press q to exit

❓ --help Option

Display brief command usage

ls --help

🔍 which/whereis Commands

Check command location

which ls whereis ls

🚨 Emergency Commands

Ctrl + C

Force stop running command

exit

Exit terminal

reset

Reset terminal

clear

Clear screen

9. Next Steps

Now that you understand terminal basics, let's learn actual Linux commands!

🎯 Step 1: Master Basic Commands

Start with the 10 most important commands

pwd ls cd mkdir touch cat cp mv rm echo
Read Basic Command Introduction →

⚡ Step 2: Hands-on Practice

Practice by actually typing commands in Penguin Gym Linux

Practice with Penguin Gym Linux →

📁 Step 3: Master File Operations

Learn more advanced file and directory operations

Read File Operations Guide (Basics) →

🔐 Step 4: Understand Permission Management

Understand Linux permission system and operate system safely

Learn Permission Management Basics →

💡 Efficient Learning Tips

  • A little every day: Even 15 minutes - consistency is key
  • Actually practice: Not just reading, but doing
  • Don't fear mistakes: Errors are part of learning
  • Take notes: Record frequently used commands

🎉 Summary

The terminal (command line) may seem difficult at first, but once you get used to it, it becomes a very powerful and efficient tool. It enables high-speed processing and automation impossible with GUI operations, and your IT skills will improve dramatically.

📝 Key Points

  • Terminal = Tool to operate computer with text
  • Current situation can be read from prompt
  • Efficient operation possible with shortcut keys
  • Understanding command structure enables application
  • Don't fear mistakes, prioritize practice

🚀 Take Action Now!

Now that you've learned the theory, try experiencing Linux commands firsthand!

🐧 Experience Terminal with Penguin Gym Linux 💻 Practice Basic Commands