Command Line Guide¶

username@computername ~ %

# See what directory you're in
pwd

# List files in current directory
ls

# Print text to screen
echo "Hello, World!"

# Clear the screen
clear

# Print Working Directory - see where you are
pwd

# List files and directories
ls

# List with details (long format)
ls -l

# List all files including hidden ones
ls -a

# List with human-readable file sizes
ls -lh

# Change directory
cd Documents

# Go to home directory
cd ~
# or just
cd

# Go up one directory
cd ..

# Go to root directory
cd /

# Go to previous directory
cd -

# Get help for any command
man ls          # Manual page for ls
man cd          # Manual page for cd

# Quick help (if available)
ls --help

# Search manual pages
man -k search_term

# View entire file
cat filename.txt

# View file page by page
less filename.txt
# Press 'q' to quit, space for next page, 'b' for previous page

# View first 10 lines
head filename.txt

# View first 20 lines
head -n 20 filename.txt

# View last 10 lines
tail filename.txt

# View last 20 lines
tail -n 20 filename.txt

# Watch a file as it updates (great for logs)
tail -f logfile.txt

# Create a new directory
mkdir my_folder

# Create nested directories
mkdir -p parent/child/grandchild

# Create an empty file
touch newfile.txt

# Create multiple files
touch file1.txt file2.txt file3.txt

# Create file with content using echo
echo "Hello World" > hello.txt

# Append to file
echo "New line" >> hello.txt

# Copy a file
cp source.txt destination.txt

# Copy a directory (recursive)
cp -r source_dir destination_dir

# Move/rename a file
mv oldname.txt newname.txt

# Move file to different directory
mv file.txt ~/Documents/

# Move multiple files
mv file1.txt file2.txt ~/Documents/

# Delete a file
rm filename.txt

# Delete multiple files
rm file1.txt file2.txt file3.txt

# Delete directory (empty)
rmdir empty_folder

# Delete directory with contents (CAREFUL!)
rm -r folder_name

# Delete with confirmation
rm -i filename.txt

# Force delete (no confirmation - DANGEROUS!)
rm -f filename.txt

# Find files by name
find . -name "*.txt"

# Find files in home directory
find ~ -name "*.py"

# Find directories
find . -type d -name "my_folder"

# Find files modified in last 7 days
find . -mtime -7

# Find files larger than 100MB
find . -size +100M

# Search for text in a file
grep "search term" filename.txt

# Case-insensitive search
grep -i "search" filename.txt

# Search in multiple files
grep "search" *.txt

# Search recursively in directories
grep -r "search" .

# Show line numbers
grep -n "search" filename.txt

# Show context (3 lines before and after)
grep -C 3 "search" filename.txt

# Count matches
grep -c "search" filename.txt

# Open file in nano (beginner-friendly editor)
nano filename.txt
# Ctrl+X to exit, Y to save, N to discard

# Open file in vim (advanced editor)
vim filename.txt
# Press 'i' to insert, 'Esc' then ':wq' to save and quit
# ':q!' to quit without saving

# Open file in VS Code from terminal
code filename.txt

# Open file in Cursor
cursor filename.txt

# Count lines, words, characters
wc filename.txt

# Count lines only
wc -l filename.txt

# Count words only
wc -w filename.txt

# Sort lines alphabetically
sort filename.txt

# Sort numerically
sort -n numbers.txt

# Remove duplicate lines
sort filename.txt | uniq

# Show unique lines with count
sort filename.txt | uniq -c

# Extract specific columns (space-separated)
cut -d' ' -f1,3 filename.txt

# Replace text
sed 's/old/new/g' filename.txt

# Replace in file (modify file)
sed -i '' 's/old/new/g' filename.txt

# Pipe output of one command to another
ls -l | grep ".txt"

# Count files in directory
ls | wc -l

# Save output to file
ls > file_list.txt

# Append output to file
echo "new line" >> file_list.txt

# Use output as input
cat file1.txt file2.txt > combined.txt

# Chain multiple commands
ls -l | grep ".txt" | wc -l

# Set a variable
MY_VAR="Hello World"

# Use a variable
echo $MY_VAR

# List all environment variables
env

# View specific variable
echo $HOME
echo $PATH

# Add to PATH
export PATH="$PATH:/new/directory"

# Use output of command as input
echo "Today is $(date)"

# Store command output in variable
FILES=$(ls *.txt)
echo $FILES

# Count files matching pattern
FILE_COUNT=$(ls *.txt | wc -l)
echo "Found $FILE_COUNT text files"

# For loop - process each file
for file in *.txt; do
    echo "Processing $file"
    wc -l "$file"
done

# For loop with numbers
for i in {1..10}; do
    echo "Number: $i"
done

# While loop
counter=1
while [ $counter -le 5 ]; do
    echo "Count: $counter"
    counter=$((counter + 1))
done

# If statement
if [ -f "file.txt" ]; then
    echo "File exists"
else
    echo "File does not exist"
fi

# Check if directory exists
if [ -d "my_folder" ]; then
    echo "Directory exists"
fi

# Check file permissions
if [ -r "file.txt" ]; then
    echo "File is readable"
fi

# Run command in background
python long_script.py &

# See background jobs
jobs

# Bring job to foreground
fg %1

# Kill a background job
kill %1

# Run command and detach (nohup)
nohup python script.py &

# Create an alias
alias ll='ls -lh'

# Create alias for common command
alias ..='cd ..'
alias ...='cd ../..'

# List all aliases
alias

# Make alias permanent (add to ~/.zshrc)
echo 'alias ll="ls -lh"' >> ~/.zshrc
source ~/.zshrc

# Install Homebrew (if not installed)
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# Install packages
brew install tree
brew install htop
brew install wget
brew install jq

# Update Homebrew
brew update

# Upgrade packages
brew upgrade

# List installed packages
brew list

# Search for packages
brew search python

# Install
brew install tree

# Show directory tree
tree

# Show tree with depth limit
tree -L 2

# Show only directories
tree -d

# Show hidden files
tree -a

# Install
brew install htop

# Run htop
htop

# Shows: CPU usage, memory, running processes
# Press 'q' to quit, 'F5' for tree view

# Install
brew install jq

# Pretty print JSON
cat data.json | jq .

# Extract specific field
cat data.json | jq '.name'

# Filter array
cat data.json | jq '.[] | select(.age > 30)'

# Install
brew install bat

# View file with syntax highlighting
bat filename.py

# Show line numbers
bat -n filename.py

# Show multiple files
bat file1.txt file2.txt

# Install
brew install fd

# Find files (faster than find)
fd "\.py$"

# Find in specific directory
fd "test" src/

# Case-insensitive search
fd -i "python"

# Install
brew install ripgrep

# Search (faster than grep)
rg "search term"

# Search in specific file types
rg "function" --type py

# Show context
rg "error" -C 3

# Install
brew install fzf

# Interactive file finder
fzf

# Search command history
# Press Ctrl+R in terminal

# Install useful key bindings
$(brew --prefix)/opt/fzf/install

# Install
brew install tldr

# Get simplified help
tldr ls
tldr git
tldr python

# Install
brew install exa

# List files (with colors and icons)
exa

# Tree view
exa --tree

# Long format with git status
exa --long --git

# Initialize repository
git init

# Check status
git status

# Add files
git add filename.txt
git add .  # Add all files

# Commit changes
git commit -m "Your message"

# View history
git log

# View changes
git diff

# Create branch
git branch new-feature

# Switch branch
git checkout new-feature

# Merge branch
git merge new-feature

# Clone repository
git clone https://github.com/user/repo.git

# Run Python script
python script.py

# Run Python interactively
python

# Install package
pip install package_name

# Install from requirements
pip install -r requirements.txt

# List installed packages
pip list

# Create virtual environment
python -m venv venv

# Activate virtual environment
source venv/bin/activate

# Deactivate
deactivate

# Create environment
conda create -n myenv python=3.10

# Activate environment
conda activate myenv

# Install package
conda install numpy

# List environments
conda env list

# Deactivate
conda deactivate

# Export environment
conda env export > environment.yml

# In Terminal:
Ctrl+A          # Move to beginning of line
Ctrl+E          # Move to end of line
Ctrl+U          # Delete to beginning of line
Ctrl+K          # Delete to end of line
Ctrl+W          # Delete previous word
Ctrl+L          # Clear screen (same as 'clear')
Ctrl+C          # Cancel current command
Ctrl+D          # Exit terminal
Ctrl+R          # Search command history
Tab             # Auto-complete
Tab Tab         # Show all completions

# View command history
history

# Search history
history | grep "python"

# Run previous command
!!

# Run command from history by number
!42

# Run last command starting with 'python'
!python

# Type part of filename and press Tab
ls Doc[TAB]     # Completes to "Documents/"

# Press Tab twice to see all options
ls D[TAB][TAB]   # Shows all files starting with 'D'

# Match any characters
ls *.txt        # All .txt files
ls file*        # All files starting with "file"

# Match single character
ls file?.txt    # file1.txt, file2.txt, etc.

# Match character range
ls file[1-5].txt

# Match specific characters
ls file[abc].txt

# Run command only if previous succeeds
command1 && command2

# Run command if previous fails
command1 || command2

# Run multiple commands sequentially
command1; command2; command3

# Run command in subshell
(cd /tmp && ls)

# Find largest files in directory
du -h . | sort -rh | head -10

# Count files by type
find . -name "*.py" | wc -l

# Find and delete old files
find . -name "*.log" -mtime +30 -delete

# Monitor file changes
watch -n 1 'ls -lht | head'

# Extract all URLs from file
grep -oP 'http[s]?://[^\s]+' file.txt

# Find duplicate files
find . -type f -exec md5 {} \; | sort | uniq -d -w 32

# Rename files in bulk
for file in *.txt; do mv "$file" "${file%.txt}.bak"; done

# Create backup of directory
tar -czf backup.tar.gz directory/

# Extract tar file
tar -xzf backup.tar.gz

# Edit zsh configuration
nano ~/.zshrc

# Add useful aliases
alias ll='ls -lh'
alias la='ls -lah'
alias ..='cd ..'
alias ...='cd ../..'
alias grep='grep --color=auto'

# Add to PATH
export PATH="$PATH:/custom/path"

# Reload configuration
source ~/.zshrc

# Install Oh My Zsh
sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

# Popular plugins to add to ~/.zshrc:
# plugins=(git python pip conda)