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Claude Code Quick Start (1-2-3)

Install → Authenticate → Code​

Step 1: Install (30 seconds)​

macOS / Linux / WSL:

curl -fsSL https://claude.ai/install.sh | bash

Windows PowerShell (Run as Admin):

irm https://claude.ai/install.ps1 | iex

Alternative (Homebrew):

brew install --cask claude-code

Alternative (npm):

npm install -g @anthropic-ai/claude-code

Step 2: Authenticate (30 seconds)​

claude auth login
  • Opens browser
  • Login to claude.ai
  • Returns to terminal
  • Done ✅

Or set API key:

export ANTHROPIC_API_KEY="sk-ant-..."

Get API key: https://console.anthropic.com/settings/keys

Step 3: Start Coding (5 seconds)​

cd your-project
claude chat

That's it. You're running.

First Commands to Try​

Basic Chat​

Hey, can you help me with this project?

Generate Code​

Create a Python FastAPI endpoint for user authentication

Fix Bugs​

Fix the error in app.py line 42

Read Files​

@app.py explain what this does

Write Code​

Add error handling to the login function

Slash Commands (Inside Claude Code)​

CommandWhat It Does
/helpShow all H.P.002-COMMANDS
/statusCheck model & tokens
/clearClear conversation
/exitExit Claude Code

Quick Tips​

Approve permissions as you go:

  • Claude asks before reading/writing files
  • Claude asks before running H.P.002-COMMANDS
  • Say "yes" to trust, "no" to block

Reference files with @:

@src/utils.py add type hints to all functions

Check what's happening:

/status

Common First Tasks​

1. Understand a Project​

cd my-project
claude chat
Analyze this codebase and explain what it does

2. Generate New Feature​

Create a REST API endpoint for creating blog posts with validation

3. Fix Errors​

I'm getting "TypeError: cannot read property 'name' of undefined" - can you help?

4. Write Tests​

Write unit tests for the UserService class

5. Refactor Code​

Refactor auth.js to use async/await instead of promises

Directory Structure (What Gets Created)​

After installation and first run:

~/.claude/
└── .claude.json          # Auth state (auto-created)

That's all. No other files are created automatically.

Optional files you can create later:

  • ~/.claude/settings.json - Advanced H.P.009-CONFIG
  • CLAUDE.md - Project context/memory
  • .claude/settings.json - Project-specific settings

Troubleshooting​

"command not found: claude"​

echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

"Invalid API key"​

claude auth login
# Or set: export ANTHROPIC_API_KEY="sk-ant-..."

Check if working​

claude --version
claude doctor

That's It!​

You're ready to code with Claude.

Three H.P.002-COMMANDS to remember:

  1. claude auth login - Authenticate
  2. claude chat - Start coding
  3. /help - Get help

Next steps:

  • Try generating some code
  • Ask Claude to explain your codebase
  • Have it write tests for you
  • Let it refactor something

Advanced (later):

  • Create CLAUDE.md for project context
  • Set up permissions in settings.json
  • Add custom H.P.002-COMMANDS
  • Configure MCP servers

Quick Reference Card​

┌─────────────────────────────────────────────┐
│  CLAUDE CODE ESSENTIALS                     │
├─────────────────────────────────────────────┤
│                                             │
│  Install:   curl -fsSL claude.ai/install.sh │
│            | bash                            │
│                                             │
│  Auth:      claude auth login               │
│                                             │
│  Start:     claude chat                     │
│                                             │
│  Exit:      /exit                           │
│                                             │
│  Help:      /help                           │
│                                             │
│  Status:    /status                         │
│                                             │
│  Mention:   @filename                       │
│                                             │
│  API Key:   console.anthropic.com/settings  │
│                                             │
└─────────────────────────────────────────────┘

One-Liner Installation + First Use​

curl -fsSL https://claude.ai/install.sh | bash && \
claude auth login && \
cd ~/my-project && \
claude chat

Done. Start coding with AI.