Command Line Essentials: Terminal Commands Every Developer Should Know
Table of Contents
Introduction
The command line might look intimidating with its black screen and blinking cursor, but it's one of the most powerful tools in a developer's toolkit. In this tutorial, you'll learn the essential terminal commands that will make you more efficient and confident as a developer.
What you'll learn:
Prerequisites:
Time to complete: 40-50 minutes
What is the Command Line?
The command line (also called terminal, console, or shell) is a text-based interface for interacting with your computer. Instead of clicking buttons and icons, you type commands to tell your computer what to do.
Real-World Analogy
Think of your computer as a restaurant:
Graphical Interface (GUI):
Command Line:
Why It Looks Scary (But Isn't)
When you open a terminal, you see something like:
user@computer:~$
This is just your computer saying "I'm ready for your command!" The blinking cursor is waiting for you to type.
Why Developers Use the Command Line
Speed and Efficiency
With GUI (multiple clicks):
With command line (one command):
mkdir -p Documents/my-project && cd Documents/my-project && touch index.html
Done in 2 seconds! ⚡
More Control and Power
Some tasks are impossible or difficult with a graphical interface:
Industry Standard
Professional developers use the command line because:
Opening Your Terminal
Windows
Option 1: Command Prompt
Option 2: PowerShell (Recommended)
Option 3: Git Bash (Best for Development)
macOS
Option 1: Spotlight
Option 2: Finder
Linux
Most distributions:
Or:
Understanding the Command Line Interface
Anatomy of the Command Prompt
When you open your terminal, you'll see something like:
john@macbook:~/Documents$
Let's break this down:
Understanding Paths
Absolute path - Complete address from the root:
/Users/john/Documents/projects/my-app
Relative path - Address from your current location:
projects/my-app # If you're already in Documents
Special path symbols:
Essential Navigation Commands
pwd - Print Working Directory
Shows where you currently are in the file system.
pwd
Output:
/Users/john/Documents
Use case: When you're lost and need to know your current location.
ls - List Directory Contents
Shows files and folders in your current location.
Basic usage:
ls
Output:
file1.txt file2.txt my-folder notes.md
Common options:
# List with details (permissions, size, date)
ls -l
# List all files including hidden ones (starting with .)
ls -a
# List in human-readable format with sizes
ls -lh
# Combine options
ls -lah
Example output with -lh:
-rw-r--r-- 1 john staff 2.5K Oct 20 14:30 file1.txt
drwxr-xr-x 3 john staff 96B Oct 20 14:30 my-folder
Reading the output:
cd - Change Directory
Moves you to a different folder.
Go to a specific folder:
cd Documents
Go to home directory:
cd ~
# or just
cd
Go up one level:
cd ..
Go up two levels:
cd ../..
Go to previous directory:
cd -
Use absolute path:
cd /Users/john/Documents/projects
Pro tip: Use Tab to autocomplete folder names!
cd Doc[press Tab]
# Autocompletes to: cd Documents/
Working with Files and Directories
mkdir - Make Directory
Creates a new folder.
Create a single folder:
mkdir my-project
Create nested folders:
mkdir -p projects/web-app/src
# Creates: projects, then web-app inside it, then src inside that
Create multiple folders at once:
mkdir folder1 folder2 folder3
touch - Create Empty File
Creates a new file or updates the timestamp of an existing file.
Create a single file:
touch index.html
Create multiple files:
touch index.html style.css script.js
Create file with path:
touch src/components/Header.js
Note: The folder must exist first, or use mkdir -p to create it.
cp - Copy Files and Directories
Copies files or folders from one location to another.
Copy a file:
cp file.txt file-backup.txt
Copy a file to another directory:
cp file.txt ../backup/
Copy a directory and its contents:
cp -r my-folder my-folder-backup
# -r means "recursive" (includes everything inside)
Copy multiple files:
cp file1.txt file2.txt file3.txt destination-folder/
mv - Move or Rename
Moves files/folders or renames them.
Rename a file:
mv oldname.txt newname.txt
Move a file to another directory:
mv file.txt Documents/
Move and rename simultaneously:
mv file.txt Documents/renamed-file.txt
Move a directory:
mv my-folder Documents/projects/
rm - Remove Files and Directories
Deletes files or folders permanently.
⚠️ WARNING: There's no "Recycle Bin" - deleted files are gone forever!
Delete a file:
rm file.txt
Delete multiple files:
rm file1.txt file2.txt file3.txt
Delete a directory and its contents:
rm -r my-folder
# -r means "recursive" (deletes everything inside)
Force delete without confirmation:
rm -rf my-folder
# -f means "force" (no confirmation prompts)
Safe deletion - ask for confirmation:
rm -i file.txt
# Prompts: "remove file.txt? (y/n)"
Pro tip: Use rm -i when starting out to avoid accidents!
find - Search for Files
Finds files and directories based on criteria.
Find by name:
find . -name "*.txt"
# Finds all .txt files in current directory and subdirectories
Find by type:
# Find only directories
find . -type d
# Find only files
find . -type f
Find and delete:
find . -name "*.log" -delete
# Finds and deletes all .log files
Find by modification time:
# Files modified in last 7 days
find . -mtime -7
# Files modified more than 30 days ago
find . -mtime +30
Viewing and Editing Files
cat - Display File Contents
Shows the entire contents of a file.
cat file.txt
Combine multiple files:
cat file1.txt file2.txt
Create a new file with content:
cat > newfile.txt
# Type your content, then press Ctrl+D to save
less - View File Contents (Paginated)
Better for large files - shows content page by page.
less largefile.txt
Navigation in less:
head - Show First Lines
Shows the beginning of a file.
# Show first 10 lines (default)
head file.txt
# Show first 5 lines
head -n 5 file.txt
tail - Show Last Lines
Shows the end of a file.
# Show last 10 lines (default)
tail file.txt
# Show last 20 lines
tail -n 20 file.txt
# Follow file updates in real-time (useful for logs)
tail -f logfile.txt
grep - Search Inside Files
Finds text within files.
Search for a word:
grep "error" logfile.txt
Search case-insensitively:
grep -i "error" logfile.txt
# Finds "error", "Error", "ERROR"
Search in multiple files:
grep "TODO" *.js
# Searches all JavaScript files
Search recursively in all subdirectories:
grep -r "function" .
Show line numbers:
grep -n "error" file.txt
Count matches:
grep -c "error" file.txt
nano / vim - Text Editors
Command-line text editors for editing files.
Using nano (easier for beginners):
nano file.txt
Nano shortcuts:
Using vim (more powerful but steeper learning curve):
vim file.txt
Vim basic commands:
Pro tip: Start with nano until you're comfortable, then learn vim if you want more power.
File Permissions and Ownership
Understanding Permissions
When you run ls -l, you see something like:
-rw-r--r-- 1 john staff 2048 Oct 20 14:30 file.txt
Permission breakdown:
-rw-r--r--
│││││││││
│││└─────── Others can read
│││
││└──────── Group can read
││
│└───────── Group cannot write
│
└────────── Owner can read and write
Permission types:
chmod - Change Permissions
Changes file/folder permissions.
Using symbolic notation:
# Give owner execute permission
chmod u+x script.sh
# Remove write permission from group
chmod g-w file.txt
# Give everyone read permission
chmod a+r file.txt
Using numeric notation:
# 755 = Owner can read/write/execute, others can read/execute
chmod 755 script.sh
# 644 = Owner can read/write, others can only read
chmod 644 file.txt
# 777 = Everyone can do everything (rarely recommended!)
chmod 777 file.txt
Common permission patterns:
chown - Change Owner
Changes file/folder ownership.
# Change owner
sudo chown newowner file.txt
# Change owner and group
sudo chown newowner:newgroup file.txt
# Change recursively
sudo chown -R newowner folder/
Note: Usually requires sudo (admin privileges).
Using Git from the Command Line
Git is the most popular version control system, and it's primarily used through the command line.
Essential Git Commands
Initialize a new repository:
git init
Check status:
git status
Add files to staging:
# Add specific file
git add file.txt
# Add all files
git add .
# Add all JavaScript files
git add *.js
Commit changes:
git commit -m "Your commit message here"
View commit history:
git log
# Compact view
git log --oneline
# Show last 5 commits
git log -n 5
Create a branch:
git branch feature-name
Switch branches:
git checkout feature-name
# Or create and switch in one command
git checkout -b feature-name
Merge branches:
# Switch to main branch first
git checkout main
# Merge feature branch
git merge feature-name
Clone a repository:
git clone https://github.com/username/repo-name.git
Pull latest changes:
git pull origin main
Push your changes:
git push origin main
View remote repositories:
git remote -v
Undo last commit (keep changes):
git reset --soft HEAD~1
Discard local changes:
# Discard changes in specific file
git checkout -- file.txt
# Discard all changes
git reset --hard
Process Management
ps - List Running Processes
Shows currently running processes.
# Show your processes
ps
# Show all processes with details
ps aux
# Find specific process
ps aux | grep node
top - Monitor System Resources
Shows real-time system resource usage.
top
Navigation:
Alternative (better): Use htop if available
htop
kill - Terminate Processes
Stops a running process.
Kill by process ID:
kill 1234
# Where 1234 is the PID (Process ID)
Force kill:
kill -9 1234
Kill by name:
killall node
# Kills all processes named "node"
Find and kill a process:
# Find the process
ps aux | grep node
# Kill it
kill 1234
Background and Foreground Processes
Run command in background:
node server.js &
# The & runs it in background
See background jobs:
jobs
Bring job to foreground:
fg %1
# Brings job #1 to foreground
Send running process to background:
Command Line Shortcuts and Tips
Keyboard Shortcuts
Navigation:
Editing:
History:
Control:
Useful Command Combinations
Pipes (|) - Send output of one command to another:
# Count files in directory
ls | wc -l
# Search for error in all logs
cat *.log | grep "error"
# Sort and show unique values
cat file.txt | sort | uniq
Redirection (> and >>) - Save output to file:
# Overwrite file with output
ls > filelist.txt
# Append output to file
echo "New line" >> notes.txt
# Redirect errors
command 2> errors.txt
# Redirect both output and errors
command > output.txt 2>&1
Command chaining:
# Run second command only if first succeeds (&&)
mkdir my-folder && cd my-folder
# Run second command regardless (
mkdir my-folder; ls
# Run second command only if first fails (||)
command || echo "Command failed"
Tab Completion
The Tab key is your best friend!
# Type part of command or filename, press Tab
cd Doc[Tab]
# Autocompletes to: cd Documents/
# Double Tab shows all possibilities
git ch[Tab][Tab]
# Shows: checkout, cherry, cherry-pick, etc.
Command History
View command history:
history
Execute command from history:
!123
# Executes command Minority AIDS Initiative: The Substa...nic Minorities from history
Search history:
# Press Ctrl+R, then type search term
# Press Ctrl+R again to cycle through matches
Clear history:
history -c
Aliases - Custom Shortcuts
Create shortcuts for frequently used commands.
Temporary alias (current session only):
alias ll='ls -lah'
# Now typing 'll' runs 'ls -lah'
Permanent aliases (add to ~/.bashrc or ~/.zshrc):
# Open config file
nano ~/.bashrc # or ~/.zshrc for Zsh
# Add aliases
alias ll='ls -lah'
alias gs='git status'
alias gc='git commit'
alias gp='git push'
# Save and reload
source ~/.bashrc
Useful aliases:
alias cls='clear'
alias ..='cd ..'
alias ...='cd ../..'
alias projects='cd ~/Documents/projects'
alias gs='git status'
alias gaa='git add .'
alias gcm='git commit -m'
Common Mistakes to Avoid
1. Deleting Without Checking
❌ Dangerous:
rm -rf *
# Deletes EVERYTHING in current directory
✅ Safe approach:
# Always check where you are first
pwd
# List what will be deleted
ls
# Then delete specific things
rm -i file.txt
2. Forgetting Spaces in Commands
❌ Wrong:
cd..
# Error: command not found
✅ Correct:
cd ..
# Space is required
3. Using Absolute Paths When Relative Would Work
❌ Unnecessary:
cd /Users/john/Documents/projects/my-app
✅ Better:
cd ~/Documents/projects/my-app
# or if you're already in Documents:
cd projects/my-app
4. Not Using Tab Completion
❌ Slow:
# Typing out full path manually
cd /Users/john/Documents/projects/very-long-folder-name
✅ Fast:
cd ~/Doc[Tab]/proj[Tab]/very[Tab]
# Let Tab complete the rest!
5. Ignoring Error Messages
Always read error messages! They tell you exactly what went wrong.
Common error:
bash: command not found: node
What it means: The command doesn't exist or isn't installed.
Solution: Install the software or check spelling.
6. Running Commands Without Understanding Them
❌ Dangerous:
# Copying random commands from the internet
sudo rm -rf /
# THIS DELETES YOUR ENTIRE SYSTEM!
✅ Safe:
Troubleshooting Guide
Issue: "Permission Denied"
Error:
bash: ./script.sh: Permission denied
Solution:
# Make file executable
chmod +x script.sh
# Then run it
./script.sh
Issue: "Command Not Found"
Error:
bash: node: command not found
Possible causes:
Solutions:
# Check if it's installed
which node
# Install if missing (example for Node.js)
# On macOS with Homebrew:
brew install node
# On Ubuntu/Debian:
sudo apt install nodejs
# Check spelling
noed # Wrong!
node # Correct!
Issue: "No Such File or Directory"
Error:
bash: cd: Documents: No such file or directory
Solutions:
# Check current location
pwd
# List what's actually there
ls
# Check spelling (case-sensitive!)
cd documents # Wrong if folder is "Documents"
cd Documents # Correct
Issue: Terminal Stuck or Frozen
Solutions:
If command is running:
If terminal is unresponsive:
If process is stuck in background:
# Find the process
ps aux | grep stuck-process
# Kill it
kill -9 PID
Issue: Accidentally Ran Wrong Command
Examples:
Deleted wrong file:
Changed wrong directory:
cd -
# Goes back to previous directory
Want to undo last change:
# For Git
git checkout -- file.txt
# For general file changes
# No built-in undo - use backups!
Issue: "Cannot Write to File"
Error:
bash: file.txt: Permission denied
Solutions:
# Check current permissions
ls -l file.txt
# Change permissions
chmod u+w file.txt
# Or use sudo (be careful!)
sudo nano file.txt
Practical Examples and Workflows
Example 1: Starting a New Project
# Create project folder and navigate into it
mkdir my-new-project && cd my-new-project
# Create project structure
mkdir src css js img
# Create initial files
touch index.html src/app.js css/style.css
# Initialize Git
git init
# Create README
echo "# My New Project" > README.md
# Check what you created
ls -la
Example 2: Finding and Cleaning Up Old Files
# Find all log files
find . -name "*.log"
# Find log files older than 30 days
find . -name "*.log" -mtime +30
# Delete them (be careful!)
find . -name "*.log" -mtime +30 -delete
# Or move them to archive
mkdir archive
find . -name "*.log" -mtime +30 -exec mv {} archive/ \;
Example 3: Working with Git
# Clone a repository
git clone https://github.com/username/repo.git
# Navigate into it
cd repo
# Create new feature branch
git checkout -b new-feature
# Make changes, then check status
git status
# Add changes
git add .
# Commit
git commit -m "Add new feature"
# Push to remote
git push origin new-feature
# Switch back to main
git checkout main
# Pull latest changes
git pull origin main
Example 4: Batch File Operations
# Rename all .txt files to .md
for file in *.txt; do
mv "$file" "${file%.txt}.md"
done
# Create 10 numbered files
for i in {1..10}; do
touch file$i.txt
done
# Find and replace text in all files
find . -name "*.txt" -exec sed -i 's/oldtext/newtext/g' {} \;
Next Steps
Now that you understand command line basics, here's how to continue learning:
Immediate Practice
Intermediate Topics
Advanced Topics
Key Takeaways
✅ The command line is faster and more powerful than graphical interfaces for many tasks
✅ Essential commands to remember:
✅ Use Tab completion to save time and avoid typos
✅ Read error messages - they usually tell you exactly what's wrong
✅ Start with safe commands - use -i flag for confirmations when learning
✅ Practice regularly - command line proficiency comes with repetition
✅ Don't fear mistakes - you can't break anything as long as you avoid sudo rm -rf
Additional Resources
About the Author: Isabella Otoo is a full-stack developer and technical writer passionate about making complex technical concepts accessible to beginners.
GitHub Repository: [https://github.com/Bellagirl-maker]
Last Updated: October 2025
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Table of Contents
- What is the Command Line?
- Why Developers Use the Command Line
- Opening Your Terminal
- Understanding the Command Line Interface
- Essential Navigation Commands
- Working with Files and Directories
- Viewing and Editing Files
- File Permissions and Ownership
- Using Git from the Command Line
- Process Management
- Command Line Shortcuts and Tips
- Common Mistakes to Avoid
- Troubleshooting Guide
Introduction
The command line might look intimidating with its black screen and blinking cursor, but it's one of the most powerful tools in a developer's toolkit. In this tutorial, you'll learn the essential terminal commands that will make you more efficient and confident as a developer.
What you'll learn:
- What the command line is and why it matters
- Essential commands for navigating your file system
- How to create, move, and delete files and folders
- Using Git from the command line
- Productivity shortcuts and tips
- How to troubleshoot common issues
Prerequisites:
- A computer running Windows, macOS, or Linux
- No prior command line experience required
- Willingness to experiment (you won't break anything!)
Time to complete: 40-50 minutes
What is the Command Line?
The command line (also called terminal, console, or shell) is a text-based interface for interacting with your computer. Instead of clicking buttons and icons, you type commands to tell your computer what to do.
Real-World Analogy
Think of your computer as a restaurant:
Graphical Interface (GUI):
- Like a picture menu where you point at what you want
- Easy to use but limited options
- Click, drag, drop
Command Line:
- Like telling the chef exactly what you want
- More powerful and flexible
- Type specific instructions
Why It Looks Scary (But Isn't)
When you open a terminal, you see something like:
user@computer:~$
This is just your computer saying "I'm ready for your command!" The blinking cursor is waiting for you to type.
Why Developers Use the Command Line
Speed and Efficiency
With GUI (multiple clicks):
- Open File Explorer
- Navigate to Documents
- Create new folder
- Name the folder
- Open the folder
- Create a new file
- Name the file
With command line (one command):
mkdir -p Documents/my-project && cd Documents/my-project && touch index.html
Done in 2 seconds! ⚡
More Control and Power
Some tasks are impossible or difficult with a graphical interface:
- Batch renaming 100 files
- Finding all files containing specific text
- Automating repetitive tasks
- Managing remote servers
- Using advanced developer tools
Industry Standard
Professional developers use the command line because:
- ✅ Many tools only have command line interfaces
- ✅ Easier to share instructions (copy-paste commands)
- ✅ Required for server management
- ✅ Essential for version control (Git)
- ✅ Faster for complex operations
Opening Your Terminal
Windows
Option 1: Command Prompt
- Press Windows key + R
- Type cmd
- Press Enter
Option 2: PowerShell (Recommended)
- Press Windows key + X
- Select "Windows PowerShell"
Option 3: Git Bash (Best for Development)
- Install Git for Windows
- Right-click anywhere → "Git Bash Here"
macOS
Option 1: Spotlight
- Press Cmd + Space
- Type "Terminal"
- Press Enter
Option 2: Finder
- Go to Applications → Utilities → Terminal
Linux
Most distributions:
- Press Ctrl + Alt + T
Or:
- Search for "Terminal" in your application menu
Understanding the Command Line Interface
Anatomy of the Command Prompt
When you open your terminal, you'll see something like:
john@macbook:~/Documents$
Let's break this down:
- john - Your username
- @ - Separator
- macbook - Your computer's name
- : - Separator
- ~/Documents - Current directory (where you are)
- $ - Prompt symbol (means you're a regular user)
- # - Root/admin prompt (if you see this, you have admin privileges)
Understanding Paths
Absolute path - Complete address from the root:
/Users/john/Documents/projects/my-app
Relative path - Address from your current location:
projects/my-app # If you're already in Documents
Special path symbols:
- ~ - Your home directory
- . - Current directory
- .. - Parent directory (one level up)
- / - Root directory (Windows uses \)
Essential Navigation Commands
pwd - Print Working Directory
Shows where you currently are in the file system.
pwd
Output:
/Users/john/Documents
Use case: When you're lost and need to know your current location.
ls - List Directory Contents
Shows files and folders in your current location.
Basic usage:
ls
Output:
file1.txt file2.txt my-folder notes.md
Common options:
# List with details (permissions, size, date)
ls -l
# List all files including hidden ones (starting with .)
ls -a
# List in human-readable format with sizes
ls -lh
# Combine options
ls -lah
Example output with -lh:
-rw-r--r-- 1 john staff 2.5K Oct 20 14:30 file1.txt
drwxr-xr-x 3 john staff 96B Oct 20 14:30 my-folder
Reading the output:
- - = file, d = directory
- rw-r--r-- = permissions
- 2.5K = file size
- Oct 20 14:30 = last modified date
cd - Change Directory
Moves you to a different folder.
Go to a specific folder:
cd Documents
Go to home directory:
cd ~
# or just
cd
Go up one level:
cd ..
Go up two levels:
cd ../..
Go to previous directory:
cd -
Use absolute path:
cd /Users/john/Documents/projects
Pro tip: Use Tab to autocomplete folder names!
cd Doc[press Tab]
# Autocompletes to: cd Documents/
Working with Files and Directories
mkdir - Make Directory
Creates a new folder.
Create a single folder:
mkdir my-project
Create nested folders:
mkdir -p projects/web-app/src
# Creates: projects, then web-app inside it, then src inside that
Create multiple folders at once:
mkdir folder1 folder2 folder3
touch - Create Empty File
Creates a new file or updates the timestamp of an existing file.
Create a single file:
touch index.html
Create multiple files:
touch index.html style.css script.js
Create file with path:
touch src/components/Header.js
Note: The folder must exist first, or use mkdir -p to create it.
cp - Copy Files and Directories
Copies files or folders from one location to another.
Copy a file:
cp file.txt file-backup.txt
Copy a file to another directory:
cp file.txt ../backup/
Copy a directory and its contents:
cp -r my-folder my-folder-backup
# -r means "recursive" (includes everything inside)
Copy multiple files:
cp file1.txt file2.txt file3.txt destination-folder/
mv - Move or Rename
Moves files/folders or renames them.
Rename a file:
mv oldname.txt newname.txt
Move a file to another directory:
mv file.txt Documents/
Move and rename simultaneously:
mv file.txt Documents/renamed-file.txt
Move a directory:
mv my-folder Documents/projects/
rm - Remove Files and Directories
Deletes files or folders permanently.
⚠️ WARNING: There's no "Recycle Bin" - deleted files are gone forever!
Delete a file:
rm file.txt
Delete multiple files:
rm file1.txt file2.txt file3.txt
Delete a directory and its contents:
rm -r my-folder
# -r means "recursive" (deletes everything inside)
Force delete without confirmation:
rm -rf my-folder
# -f means "force" (no confirmation prompts)
Safe deletion - ask for confirmation:
rm -i file.txt
# Prompts: "remove file.txt? (y/n)"
Pro tip: Use rm -i when starting out to avoid accidents!
find - Search for Files
Finds files and directories based on criteria.
Find by name:
find . -name "*.txt"
# Finds all .txt files in current directory and subdirectories
Find by type:
# Find only directories
find . -type d
# Find only files
find . -type f
Find and delete:
find . -name "*.log" -delete
# Finds and deletes all .log files
Find by modification time:
# Files modified in last 7 days
find . -mtime -7
# Files modified more than 30 days ago
find . -mtime +30
Viewing and Editing Files
cat - Display File Contents
Shows the entire contents of a file.
cat file.txt
Combine multiple files:
cat file1.txt file2.txt
Create a new file with content:
cat > newfile.txt
# Type your content, then press Ctrl+D to save
less - View File Contents (Paginated)
Better for large files - shows content page by page.
less largefile.txt
Navigation in less:
- Space - Next page
- b - Previous page
- q - Quit
- /search-term - Search forward
- ?search-term - Search backward
- G - Go to end
- g - Go to beginning
head - Show First Lines
Shows the beginning of a file.
# Show first 10 lines (default)
head file.txt
# Show first 5 lines
head -n 5 file.txt
tail - Show Last Lines
Shows the end of a file.
# Show last 10 lines (default)
tail file.txt
# Show last 20 lines
tail -n 20 file.txt
# Follow file updates in real-time (useful for logs)
tail -f logfile.txt
grep - Search Inside Files
Finds text within files.
Search for a word:
grep "error" logfile.txt
Search case-insensitively:
grep -i "error" logfile.txt
# Finds "error", "Error", "ERROR"
Search in multiple files:
grep "TODO" *.js
# Searches all JavaScript files
Search recursively in all subdirectories:
grep -r "function" .
Show line numbers:
grep -n "error" file.txt
Count matches:
grep -c "error" file.txt
nano / vim - Text Editors
Command-line text editors for editing files.
Using nano (easier for beginners):
nano file.txt
Nano shortcuts:
- Ctrl + O - Save (Write Out)
- Ctrl + X - Exit
- Ctrl + K - Cut line
- Ctrl + U - Paste
- Ctrl + W - Search
Using vim (more powerful but steeper learning curve):
vim file.txt
Vim basic commands:
- i - Enter insert mode (start typing)
- Esc - Exit insert mode
- :w - Save
- :q - Quit
- :wq - Save and quit
- :q! - Quit without saving
Pro tip: Start with nano until you're comfortable, then learn vim if you want more power.
File Permissions and Ownership
Understanding Permissions
When you run ls -l, you see something like:
-rw-r--r-- 1 john staff 2048 Oct 20 14:30 file.txt
Permission breakdown:
-rw-r--r--
│││││││││
│││└─────── Others can read
│││
││└──────── Group can read
││
│└───────── Group cannot write
│
└────────── Owner can read and write
Permission types:
- r - Read (4)
- w - Write (2)
- x - Execute (1)
- - - No permission (0)
chmod - Change Permissions
Changes file/folder permissions.
Using symbolic notation:
# Give owner execute permission
chmod u+x script.sh
# Remove write permission from group
chmod g-w file.txt
# Give everyone read permission
chmod a+r file.txt
Using numeric notation:
# 755 = Owner can read/write/execute, others can read/execute
chmod 755 script.sh
# 644 = Owner can read/write, others can only read
chmod 644 file.txt
# 777 = Everyone can do everything (rarely recommended!)
chmod 777 file.txt
Common permission patterns:
- 755 - Executable files (scripts)
- 644 - Regular files
- 600 - Private files (only owner can read/write)
chown - Change Owner
Changes file/folder ownership.
# Change owner
sudo chown newowner file.txt
# Change owner and group
sudo chown newowner:newgroup file.txt
# Change recursively
sudo chown -R newowner folder/
Note: Usually requires sudo (admin privileges).
Using Git from the Command Line
Git is the most popular version control system, and it's primarily used through the command line.
Essential Git Commands
Initialize a new repository:
git init
Check status:
git status
Add files to staging:
# Add specific file
git add file.txt
# Add all files
git add .
# Add all JavaScript files
git add *.js
Commit changes:
git commit -m "Your commit message here"
View commit history:
git log
# Compact view
git log --oneline
# Show last 5 commits
git log -n 5
Create a branch:
git branch feature-name
Switch branches:
git checkout feature-name
# Or create and switch in one command
git checkout -b feature-name
Merge branches:
# Switch to main branch first
git checkout main
# Merge feature branch
git merge feature-name
Clone a repository:
git clone https://github.com/username/repo-name.git
Pull latest changes:
git pull origin main
Push your changes:
git push origin main
View remote repositories:
git remote -v
Undo last commit (keep changes):
git reset --soft HEAD~1
Discard local changes:
# Discard changes in specific file
git checkout -- file.txt
# Discard all changes
git reset --hard
Process Management
ps - List Running Processes
Shows currently running processes.
# Show your processes
ps
# Show all processes with details
ps aux
# Find specific process
ps aux | grep node
top - Monitor System Resources
Shows real-time system resource usage.
top
Navigation:
- q - Quit
- M - Sort by memory usage
- P - Sort by CPU usage
- k - Kill a process (enter PID when prompted)
Alternative (better): Use htop if available
htop
kill - Terminate Processes
Stops a running process.
Kill by process ID:
kill 1234
# Where 1234 is the PID (Process ID)
Force kill:
kill -9 1234
Kill by name:
killall node
# Kills all processes named "node"
Find and kill a process:
# Find the process
ps aux | grep node
# Kill it
kill 1234
Background and Foreground Processes
Run command in background:
node server.js &
# The & runs it in background
See background jobs:
jobs
Bring job to foreground:
fg %1
# Brings job #1 to foreground
Send running process to background:
- Press Ctrl + Z (pauses process)
- Type bg (resumes in background)
Command Line Shortcuts and Tips
Keyboard Shortcuts
Navigation:
- Ctrl + A - Move to beginning of line
- Ctrl + E - Move to end of line
- Ctrl + Left/Right Arrow - Move word by word
Editing:
- Ctrl + U - Delete from cursor to beginning of line
- Ctrl + K - Delete from cursor to end of line
- Ctrl + W - Delete word before cursor
History:
- Up Arrow - Previous command
- Down Arrow - Next command
- Ctrl + R - Search command history (type to search, Enter to execute)
- !! - Repeat last command
- !$ - Use last argument from previous command
Control:
- Ctrl + C - Cancel current command
- Ctrl + D - Exit terminal (or end input)
- Ctrl + L - Clear screen (same as clear command)
- Ctrl + Z - Pause current process
Useful Command Combinations
Pipes (|) - Send output of one command to another:
# Count files in directory
ls | wc -l
# Search for error in all logs
cat *.log | grep "error"
# Sort and show unique values
cat file.txt | sort | uniq
Redirection (> and >>) - Save output to file:
# Overwrite file with output
ls > filelist.txt
# Append output to file
echo "New line" >> notes.txt
# Redirect errors
command 2> errors.txt
# Redirect both output and errors
command > output.txt 2>&1
Command chaining:
# Run second command only if first succeeds (&&)
mkdir my-folder && cd my-folder
# Run second command regardless (
mkdir my-folder; ls
# Run second command only if first fails (||)
command || echo "Command failed"
Tab Completion
The Tab key is your best friend!
# Type part of command or filename, press Tab
cd Doc[Tab]
# Autocompletes to: cd Documents/
# Double Tab shows all possibilities
git ch[Tab][Tab]
# Shows: checkout, cherry, cherry-pick, etc.
Command History
View command history:
history
Execute command from history:
!123
# Executes command Minority AIDS Initiative: The Substa...nic Minorities from history
Search history:
# Press Ctrl+R, then type search term
# Press Ctrl+R again to cycle through matches
Clear history:
history -c
Aliases - Custom Shortcuts
Create shortcuts for frequently used commands.
Temporary alias (current session only):
alias ll='ls -lah'
# Now typing 'll' runs 'ls -lah'
Permanent aliases (add to ~/.bashrc or ~/.zshrc):
# Open config file
nano ~/.bashrc # or ~/.zshrc for Zsh
# Add aliases
alias ll='ls -lah'
alias gs='git status'
alias gc='git commit'
alias gp='git push'
# Save and reload
source ~/.bashrc
Useful aliases:
alias cls='clear'
alias ..='cd ..'
alias ...='cd ../..'
alias projects='cd ~/Documents/projects'
alias gs='git status'
alias gaa='git add .'
alias gcm='git commit -m'
Common Mistakes to Avoid
1. Deleting Without Checking
❌ Dangerous:
rm -rf *
# Deletes EVERYTHING in current directory
✅ Safe approach:
# Always check where you are first
pwd
# List what will be deleted
ls
# Then delete specific things
rm -i file.txt
2. Forgetting Spaces in Commands
❌ Wrong:
cd..
# Error: command not found
✅ Correct:
cd ..
# Space is required
3. Using Absolute Paths When Relative Would Work
❌ Unnecessary:
cd /Users/john/Documents/projects/my-app
✅ Better:
cd ~/Documents/projects/my-app
# or if you're already in Documents:
cd projects/my-app
4. Not Using Tab Completion
❌ Slow:
# Typing out full path manually
cd /Users/john/Documents/projects/very-long-folder-name
✅ Fast:
cd ~/Doc[Tab]/proj[Tab]/very[Tab]
# Let Tab complete the rest!
5. Ignoring Error Messages
Always read error messages! They tell you exactly what went wrong.
Common error:
bash: command not found: node
What it means: The command doesn't exist or isn't installed.
Solution: Install the software or check spelling.
6. Running Commands Without Understanding Them
❌ Dangerous:
# Copying random commands from the internet
sudo rm -rf /
# THIS DELETES YOUR ENTIRE SYSTEM!
✅ Safe:
- Read what the command does first
- Use man command to read documentation
- Test on unimportant files first
- Ask if you're unsure
Troubleshooting Guide
Issue: "Permission Denied"
Error:
bash: ./script.sh: Permission denied
Solution:
# Make file executable
chmod +x script.sh
# Then run it
./script.sh
Issue: "Command Not Found"
Error:
bash: node: command not found
Possible causes:
- Software not installed
- Not in your PATH
- Typo in command name
Solutions:
# Check if it's installed
which node
# Install if missing (example for Node.js)
# On macOS with Homebrew:
brew install node
# On Ubuntu/Debian:
sudo apt install nodejs
# Check spelling
noed # Wrong!
node # Correct!
Issue: "No Such File or Directory"
Error:
bash: cd: Documents: No such file or directory
Solutions:
# Check current location
pwd
# List what's actually there
ls
# Check spelling (case-sensitive!)
cd documents # Wrong if folder is "Documents"
cd Documents # Correct
Issue: Terminal Stuck or Frozen
Solutions:
If command is running:
- Press Ctrl + C to cancel
If terminal is unresponsive:
- Press Ctrl + D to close
- Open new terminal window
If process is stuck in background:
# Find the process
ps aux | grep stuck-process
# Kill it
kill -9 PID
Issue: Accidentally Ran Wrong Command
Examples:
Deleted wrong file:
- If you used rm, file is gone (no undo)
- Check backups or Time Machine (macOS)
- Use git checkout file if it's in Git
Changed wrong directory:
cd -
# Goes back to previous directory
Want to undo last change:
# For Git
git checkout -- file.txt
# For general file changes
# No built-in undo - use backups!
Issue: "Cannot Write to File"
Error:
bash: file.txt: Permission denied
Solutions:
# Check current permissions
ls -l file.txt
# Change permissions
chmod u+w file.txt
# Or use sudo (be careful!)
sudo nano file.txt
Practical Examples and Workflows
Example 1: Starting a New Project
# Create project folder and navigate into it
mkdir my-new-project && cd my-new-project
# Create project structure
mkdir src css js img
# Create initial files
touch index.html src/app.js css/style.css
# Initialize Git
git init
# Create README
echo "# My New Project" > README.md
# Check what you created
ls -la
Example 2: Finding and Cleaning Up Old Files
# Find all log files
find . -name "*.log"
# Find log files older than 30 days
find . -name "*.log" -mtime +30
# Delete them (be careful!)
find . -name "*.log" -mtime +30 -delete
# Or move them to archive
mkdir archive
find . -name "*.log" -mtime +30 -exec mv {} archive/ \;
Example 3: Working with Git
# Clone a repository
git clone https://github.com/username/repo.git
# Navigate into it
cd repo
# Create new feature branch
git checkout -b new-feature
# Make changes, then check status
git status
# Add changes
git add .
# Commit
git commit -m "Add new feature"
# Push to remote
git push origin new-feature
# Switch back to main
git checkout main
# Pull latest changes
git pull origin main
Example 4: Batch File Operations
# Rename all .txt files to .md
for file in *.txt; do
mv "$file" "${file%.txt}.md"
done
# Create 10 numbered files
for i in {1..10}; do
touch file$i.txt
done
# Find and replace text in all files
find . -name "*.txt" -exec sed -i 's/oldtext/newtext/g' {} \;
Next Steps
Now that you understand command line basics, here's how to continue learning:
Immediate Practice
- Complete all examples in this tutorial
- Navigate your file system using only the terminal
- Try creating a project structure from scratch
- Practice Git commands with a test repository
- Create useful aliases for your workflow
Intermediate Topics
- Shell scripting and automation
- Advanced Git workflows (rebase, cherry-pick)
- Package managers (Homebrew, apt, npm)
- Environment variables and PATH
- SSH and remote server access
- Cron jobs for scheduling tasks
Advanced Topics
- Regular expressions with grep and sed
- AWK for text processing
- System administration commands
- Network commands (ping, curl, wget)
- Process management and system monitoring
- Custom shell scripts and functions
Key Takeaways
✅ The command line is faster and more powerful than graphical interfaces for many tasks
✅ Essential commands to remember:
- cd - Navigate directories
- ls - List contents
- pwd - Show current location
- mkdir - Create directories
- touch - Create files
- cp - Copy
- mv - Move/rename
- rm - Delete (careful!)
- cat / less - View files
- grep - Search in files
✅ Use Tab completion to save time and avoid typos
✅ Read error messages - they usually tell you exactly what's wrong
✅ Start with safe commands - use -i flag for confirmations when learning
✅ Practice regularly - command line proficiency comes with repetition
✅ Don't fear mistakes - you can't break anything as long as you avoid sudo rm -rf
Additional Resources
- Explain Shell - Paste any command to see what it does
- Command Line Challenge - Practice with challenges
- The Linux Command Line Book - Free comprehensive guide
- Git Documentation - Official Git resources
- Oh My Zsh - Make your terminal more powerful and beautiful
About the Author: Isabella Otoo is a full-stack developer and technical writer passionate about making complex technical concepts accessible to beginners.
GitHub Repository: [https://github.com/Bellagirl-maker]
Last Updated: October 2025
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