Claude Code

Claude Code is Anthropic's official terminal-based AI coding tool. It lets you interact with Claude directly from the command line to write code, debug issues, manage projects, and perform complex code reviews -- all without leaving your terminal.

Prerequisites

Before installing Claude Code, make sure you have the following:

• Node.js 18+ -- Required for the npm installation method. See the AI Tools overview for installation instructions.
• Anthropic API Key or Claude Pro/Max subscription -- You need one of these to authenticate.
• Internet connection -- Claude Code communicates with Anthropic's API.

TIP

You can check your Node.js version at any time with node --version. If the output shows v18 or higher, you are ready to proceed.

Installation

Method 1: Native Installer (Recommended)

The native installer handles everything automatically, including path setup.

# Download and run the official installer
curl -fsSL https://claude.ai/install.sh | bash

# Refresh your shell environment
source ~/.bashrc

# Verify the installation
claude --version

Method 2: Install via npm

If you already have Node.js and npm set up, you can install Claude Code globally with npm.

# Install Claude Code globally
npm install -g @anthropic-ai/claude-code

# Verify the installation
claude --version

Authentication & Configuration

Claude Code supports two authentication methods. Choose the one that matches your account type.

Option 1: API Key Authentication

If you have an Anthropic API key, set it as an environment variable.

# Set the API key for the current session
export ANTHROPIC_API_KEY='your-api-key-here'

# To make it persistent across sessions, add it to your shell config
echo 'export ANTHROPIC_API_KEY="your-api-key-here"' >> ~/.bashrc
source ~/.bashrc

WARNING

Keep your API key secret. Never commit it to version control or share it publicly. Consider using a secrets manager for production workflows.

Option 2: OAuth Authentication (Claude Pro/Max)

If you have a Claude Pro or Max subscription, Claude Code can authenticate through your browser.

# Simply run Claude Code -- it will open your browser for authentication on first launch
claude

Follow the on-screen prompts to complete the OAuth flow.

Basic Usage

Interactive Mode

Start an interactive session where you can have a back-and-forth conversation with Claude about your code.

# Start an interactive session in the current directory
claude

# Start in a specific project directory
cd /path/to/project
claude

One-Shot Prompts

Send a single prompt and get an immediate response without entering interactive mode.

# Ask Claude to explain code
claude "explain what this code does"

# Ask Claude to suggest improvements
claude "review this project for potential bugs"

Piping Content

You can pipe files or command output directly into Claude Code for analysis.

# Analyze an error log
cat error.log | claude "analyze this error log and suggest fixes"

# Review a specific file
cat src/main.py | claude "review this code for security issues"

# Pipe diff output for review
git diff | claude "review these changes"

Getting Help

# View all available options
claude --help

Common Commands

When inside an interactive Claude Code session, you can use the following slash commands:

Command	Description
/init	Initialize a project-level CLAUDE.md configuration file
/compact	Compress the conversation context to save tokens
/clear	Clear the current conversation history
/cost	Display token usage and cost for the current session
Tab	Accept a suggested code change
Escape	Reject a suggested code change

Update & Uninstall

Updating Claude Code

# Update using the built-in command
claude update

# Or update via npm
npm update -g @anthropic-ai/claude-code

Uninstalling Claude Code

# Uninstall via npm
npm uninstall -g @anthropic-ai/claude-code

Troubleshooting

"command not found" after installation

If claude is not recognized after installation, your PATH may not include the npm global bin directory.

# Check where npm installs global binaries
npm config get prefix

# Add the npm bin directory to your PATH (adjust the path if needed)
echo 'export PATH="$HOME/.npm-global/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

Authentication failures

If authentication fails, verify the following:

1. API Key: Make sure ANTHROPIC_API_KEY is set correctly -- echo $ANTHROPIC_API_KEY should display your key.
2. OAuth: Try clearing your browser cookies for claude.ai and running claude again.
3. Network: Make sure your system can reach api.anthropic.com -- curl -I https://api.anthropic.com should return a response.

Network timeouts or connection errors

# Test connectivity to Anthropic's API
curl -v https://api.anthropic.com

# If you are behind a proxy, set the proxy environment variables
export HTTP_PROXY="http://your-proxy:port"
export HTTPS_PROXY="http://your-proxy:port"

Permission denied during installation

# If npm install fails with EACCES, configure a user-level global directory
mkdir -p ~/.npm-global
npm config set prefix '~/.npm-global'
echo 'export PATH="$HOME/.npm-global/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

# Then retry the installation
npm install -g @anthropic-ai/claude-code

Related Resources

• AI Tools Overview -- Overview of all AI tools on Debian
• Command Line Basics -- Terminal fundamentals
• Anthropic Documentation -- Official Claude Code documentation