Command Line Cheatsheet

The command line (also called the terminal or shell) is a text interface for giving instructions to your computer. As a developer, you will use it daily to run programs, navigate files, install packages, and use Git. Comfort with the terminal is essential for web development.

Opening the terminal

macOS: Press Cmd+Space, type “Terminal”, press Enter. Or find it in Applications > Utilities > Terminal.
Windows: Use Git Bash (installed with Git for Windows), or Windows Terminal with PowerShell.
Linux: Ctrl+Alt+T opens the terminal on most distributions.

Understanding paths

Files and folders on your computer are organised in a tree structure starting from a root directory.

Absolute path: starts from the root. Always works regardless of where you are.

/Users/hannah/Documents/project/index.js   # macOS / Linux
C:\Users\hannah\Documents\project\index.js  # Windows

Relative path: starts from your current directory. Shorter, but depends on where you are.

./src/index.js    # ./ means "current directory"
../index.js       # ../ means "one level up"
../../config.js   # two levels up

Use ~ as a shortcut for your home directory:

~/Documents/project

Where am I? (pwd)

pwd stands for print working directory. It shows the full path of the folder you are currently in.

pwd
# /Users/hannah/Documents/project

What is in this folder? (ls)

ls lists the files and folders in the current directory.

ls

Common options:

ls -a        # show hidden files (files starting with .)
ls -l        # show as a list with permissions, size, and date
ls -la       # list format including hidden files
ls -lt       # sort by last modified time

Move to a different folder (cd)

cd (change directory) moves you into a folder.

cd Documents
cd Documents/project    # move into a nested folder
cd ..                   # go up one level
cd ../..                # go up two levels
cd ~                    # go to your home directory
cd -                    # go back to the previous directory

There is a space between cd and the path. cd.. without a space may work in some shells, but cd .. is correct and portable.

Creating files and folders

Create a folder (mkdir)

mkdir my-project                   # create one folder
mkdir -p src/components/buttons    # create nested folders in one command

Create a file (touch)

touch index.js
touch .env .gitignore              # create multiple files at once

touch creates an empty file. If the file already exists, it updates its timestamp.

Write output to a file

echo "Hello, world" > hello.txt    # create or overwrite the file
echo "Another line" >> hello.txt   # append to the file

Copying, moving, and renaming

Copy a file (cp)

cp original.txt copy.txt           # copy a file to a new file
cp index.js src/index.js           # copy a file into a folder
cp -r src/ backup/                 # copy a folder and all its contents (-r means recursive)

Move or rename a file (mv)

mv moves a file to a new location. If you give it a new name in the same folder, it renames the file.

mv old-name.txt new-name.txt       # rename a file
mv index.js src/index.js           # move a file into a folder
mv src/ app/                       # rename a folder

Deleting files and folders

Warning: Deletions in the terminal are permanent. There is no Trash or Undo. Double-check the path before pressing Enter.

Delete a file (rm)

rm unwanted.txt

Delete a folder and its contents (rm -r)

rm -r old-folder/

Warning: rm -r deletes everything inside a folder recursively and cannot be undone. Never run rm -rf / or rm -rf ~ or similar commands. These will wipe your entire filesystem or home directory.

Viewing file contents

Print a file to the terminal (cat)

cat index.js
cat package.json

Useful for short files. For long files, use less.

Scroll through a long file (less)

less README.md

Inside less:

Arrow keys or j / k to scroll
/search-term to search
q to quit

Print a line of text (echo)

echo "Hello, world"
echo $HOME              # print the value of an environment variable

Searching

Search inside files (grep)

grep searches for a text pattern in files and prints matching lines.

grep "function" index.js        # find lines containing "function"
grep -r "TODO" src/             # search recursively in a folder
grep -n "import" app.js         # show line numbers with matches
grep -i "error" logs.txt        # case-insensitive search

Find files by name (find)

find . -name "*.js"             # find all .js files in the current folder
find . -name ".env"             # find a specific file
find src/ -name "*.test.js"     # find test files inside src/

Sort and filter output

sort names.txt                  # sort lines alphabetically
sort -r names.txt               # reverse sort
uniq names.txt                  # remove duplicate adjacent lines
sort names.txt | uniq           # sort then remove duplicates

Redirect and pipes

# Send output of a command to a file
ls > filelist.txt               # overwrite
ls >> filelist.txt              # append

# Pipe the output of one command into another
cat names.txt | sort | uniq
grep "error" app.log | less

Useful shortcuts

Stop a running process: Ctrl+C

When you start a dev server (npm run dev, node index.js, etc.) it keeps running until you stop it. Press Ctrl+C to stop any running process.

Clear the screen

clear

Or press Ctrl+L.

Search command history

Press the Up arrow to cycle through previous commands. Press Ctrl+R and start typing to search through history.

Tab completion

Start typing a file or folder name and press Tab to autocomplete. This saves typing and prevents typos in paths.

Find and replace in files (sed)

sed is a text processing tool. The most common use is find-and-replace:

sed 's/old-text/new-text/' input.txt

s stands for substitute
The first /word/ is what to find
The second /word/ is the replacement

This prints the result without changing the original file. To save the change in place, use -i:

sed -i 's/localhost/example.com/g' config.txt

Environment variables

Environment variables store configuration values that your shell and programs can read.

echo $HOME       # print the home directory path
echo $PATH       # print the directories the shell searches for commands

Set a temporary variable for the current session:

export PORT=3000

For variables that should persist across sessions, add export lines to your shell config (~/.zshrc on macOS with zsh, ~/.bashrc on Linux with bash).

For project-specific variables, use a .env file with the dotenv package. See the Environment Variables page .

Running programs

node index.js       # run a Node.js file
npm install         # install npm packages
npm run dev         # run an npm script
python script.py    # run a Python file

Most dev tools run as a process in the terminal until you press Ctrl+C.