Claude Code CLI: when the terminal beats the IDE

# macOS, Linux, WSL
curl -fsSL https://claude.ai/install.sh | bash

# Windows PowerShell
irm https://claude.ai/install.ps1 | iex

# Homebrew (macOS): doesn't update itself, use brew upgrade claude-code
brew install --cask claude-code

# Via npm (needs Node.js 22+): also works
npm install -g @anthropic-ai/claude-code

# Check the installation
claude --version

# First launch: browser sign-in opens
claude

cd my-project/
claude
# A full chat opens inside the terminal

# Asks a question and prints the answer right away
claude -p "Write a Python function that calculates sales tax"

# Pick the model
claude -p --model haiku "I need a quick answer"

# Cap the budget
claude -p --max-budget-usd 0.10 "Review this code"

# Analyze a file
cat server.log | claude -p "Find the errors and explain the causes"

# Analyze code
cat app.py | claude -p "Find potential bugs in this code"

# Analyze the output of another command
git diff HEAD~3 | claude -p "Write a changelog for these changes"

# Data from JSON
curl -s api.example.com/data.json | claude -p "Find anomalies in the data"

# Claude reads the file and answers the question
claude -p "What does this code do?" < main.py

# Several files through a temporary file
cat requirements.txt Dockerfile > /tmp/context.txt
claude -p "Are there any version conflicts?" < /tmp/context.txt

#!/usr/bin/env bash
# daily-code-review.sh: runs every morning at 09:00

cd ~/project/

# Collect yesterday's changes
CHANGES=$(git log --since="1 day ago" --oneline)

if [ -z "$CHANGES" ]; then
  echo "No changes"
  exit 0
fi

# Send to Claude for analysis
SUMMARY=$(echo "$CHANGES" | claude -p "
Analyze these git commits from yesterday.
Point out: the main changes, possible risks, what should be tested.
Format: short bullets, no more than 200 words.
")

# Send to Telegram
curl -s -X POST "https://api.telegram.org/bot${BOT_TOKEN}/sendMessage" \
  --data-urlencode "chat_id=${CHAT_ID}" \
  --data-urlencode "text=📊 Yesterday's summary:\n${SUMMARY}"

#!/usr/bin/env bash
# generate-docs.sh

for file in src/**/*.py; do
  echo "Documenting: $file"
  
  # Generate a docstring for every function
  # (work in a separate git branch and check git diff: the model may add extra text)
  DOCS=$(cat "$file" | claude -p "
  Add detailed docstrings to every function in this Python file.
  Format: Google Style. Return only the code with the docstrings added.
  ")
  
  # Overwrite the file
  echo "$DOCS" > "$file"
done

echo "Documentation updated!"

#!/usr/bin/env bash
# pre-commit-review.sh (can be added to .git/hooks/pre-commit)

STAGED=$(git diff --cached)

if [ -z "$STAGED" ]; then
  exit 0
fi

REVIEW=$(echo "$STAGED" | claude -p "
You are an experienced code reviewer.
Check these changes for: bugs, security issues, bad practices.
If everything is fine, reply PASS.
If there are problems, list them briefly.
")

echo "$REVIEW"

# If Claude found problems, block the commit
if [[ "$REVIEW" != *"PASS"* ]]; then
  echo "❌ Code review found problems. Fix them and try again."
  exit 1
fi

echo "✅ Code review passed"
exit 0

# Create a separate folder for a new feature
git worktree add ../project-feature-X feature/new-payment

# In the main folder: current work
cd ~/project/
claude  # Working on the main branch

# In the neighboring folder: another Claude
cd ~/project-feature-X/
claude  # The second Claude works on the feature independently

# Main flags
claude -p "request"                         # Print mode (no interaction)
claude -p --model haiku                     # Pick a model by alias (sonnet, opus, haiku, fable) or full name
claude -p --max-budget-usd 0.50             # Cost cap (print mode only)
claude -p --max-turns 3                     # Cap on the number of agent steps
claude -p --tools ""                        # Disable all built-in tools (safety)
claude -p --output-format json              # Output as JSON

# Working with context
claude --add-dir ../lib                     # Give access to an extra folder
claude --append-system-prompt "Answer in Spanish"  # Add a rule to the system prompt (the instructions to the AI)

# Autonomous mode
claude --dangerously-skip-permissions       # Skip confirmations (for CI)
# Use only in isolated environments (Docker, GitHub Actions)!
# Full list of flags: https://code.claude.com/docs/en/cli-reference

# .github/workflows/ai-review.yml
name: AI Code Review

on: [pull_request]

jobs:
  ai-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
        with:
          fetch-depth: 0
      
      - name: Install Claude Code CLI
        run: npm install -g @anthropic-ai/claude-code
      
      - name: Get PR diff
        run: git diff origin/main...HEAD > /tmp/pr-diff.txt
      
      - name: AI Review
        env:
          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
        run: |
          # --tools "": PR text is untrusted (prompt injection), so Claude only reads the diff and replies, with no tools
          REVIEW=$(cat /tmp/pr-diff.txt | claude -p \
            --tools "" \
            --max-budget-usd 1.00 \
            "Review this PR for bugs and security issues. Be brief.")
          echo "## AI Code Review" >> $GITHUB_STEP_SUMMARY
          echo "$REVIEW" >> $GITHUB_STEP_SUMMARY