# macOS, Linux, WSL
curl -fsSL https://claude.ai/install.sh | bash
 
# Windows PowerShell
irm https://claude.ai/install.ps1 | iex
 
claude --version

claude auth login    # OAuth flow (use --console for API billing)
claude auth status   # check login state (JSON; --text for readable output)
# or set env var:
export ANTHROPIC_API_KEY=sk-ant-...

claude -p "Explain what this function does" < src/auth.ts
echo "Review this diff for bugs" | claude -p

# JSON output for scripting (text answer is in the "result" field)
claude -p --output-format json "List all API endpoints in this project"
 
# Streaming JSON (newline-delimited events) for real-time processing
claude -p --output-format stream-json --verbose "Generate 50 test cases for the auth module"

claude --model opus "Design the database schema..."
claude --model sonnet "Fix this bug..."
claude --model claude-opus-5-5 "..."   # full model ID

claude --effort high "Find the race condition in the job queue"

claude -p --max-budget-usd 2.00 "Write a one-paragraph summary of README.md"

claude -p --max-turns 10 "Refactor the auth module"

# Auto-approve git inspection commands and file reads
claude "Summarize this week's changes" --allowedTools "Bash(git log *)" "Bash(git diff *)" "Read"
 
# Auto-approve edits in a headless run
claude -p "Fix the typos in docs/" --allowedTools "Read" "Edit"

# Read-only audit — no writes or shell commands available
claude --tools "Read,Glob,Grep" "Audit all API routes for missing auth checks"

# Remove shell access entirely
claude "Refactor the auth module" --disallowedTools "Bash"
 
# Keep Bash, but block destructive commands
claude "Clean up the build scripts" --disallowedTools "Bash(rm *)"

claude --permission-mode plan "Add OAuth2 authentication"
# Claude researches and proposes a plan without editing files.
# Approve the plan in the session to let it start implementing.

claude --dangerously-skip-permissions "Run all tests and fix any failures"

claude -c                         # continue most recent conversation
claude --resume                   # pick from recent sessions
claude --resume auth-refactor     # resume by name or ID
claude -n "auth-refactor"         # name a new session so you can resume it later
claude --resume abc123 --fork-session   # branch into a new session ID

claude --verbose "Implement the user service"

claude --debug='mcp,startup'

{
  "$schema": "https://json.schemastore.org/claude-code-settings.json",
  "model": "opus",
 
  "permissions": {
    "allow": [
      "Bash(npm test)",
      "Bash(npm run lint)",
      "Edit(src/**)",
      "Read(**)"
    ],
    "deny": [
      "Bash(rm -rf *)",
      "Bash(git push *)",
      "Read(./.env)"
    ]
  },
 
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [{
          "type": "command",
          "command": "jq -r '.tool_input.command' >> ~/.claude/audit.log"
        }]
      }
    ],
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [{
          "type": "command",
          "command": "jq -r '.tool_input.file_path' | xargs npx eslint --fix 2>/dev/null || true"
        }]
      }
    ]
  },
 
  "env": {
    "NODE_ENV": "development"
  }
}

claude --tools "Read,Glob,Grep" \
  "Audit all API routes in src/routes/ for missing authentication middleware. 
   Report file, line number, and the missing check."

find src/lib -name "*.ts" | while read f; do
  claude -p "Add JSDoc to all exported functions in $f that lack documentation" \
    --allowedTools "Read" "Edit"
done

git diff origin/main...HEAD | \
  claude -p --output-format json \
    "Scan for: hardcoded secrets, SQL injection, missing input validation. 
     Return JSON array: [{file, line, severity, issue}]" \
  | jq -r '.result'

claude -p --dangerously-skip-permissions \
  --max-turns 30 \
  "Generate Jest tests for all functions in src/utils/ that currently have <60% coverage.
   Run npm run test:coverage after each file to verify. Commit changes when done."

claude "query"                # Start interactive session with an initial prompt
claude update                 # Update to latest version
claude install stable         # Install/reinstall a version or channel
claude doctor                 # Installation and settings diagnostics
claude auth login             # Authenticate
claude auth logout            # Remove credentials
claude auth status            # Show auth status
claude setup-token            # Long-lived OAuth token for CI (subscription required)
claude mcp                    # Configure MCP servers
claude plugin                 # Manage plugins
claude agents                 # Agent view for parallel background sessions