Introduction to Claude Code: Basics and Beyond

Terminal (CLI) Access

The command-line interface provides a powerful and flexible way to interact with Claude Code, especially for users who prefer a text-based environment or need to integrate it into scripts and CI/CD pipelines.

Installation

Claude Code CLI can be installed using various methods depending on your operating system. The native install is generally recommended.

For macOS, Linux, and WSL:

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

For Windows PowerShell:

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

For Windows CMD:

curl -fsSL https://claude.ai/install.cmd -o install.cmd && install.cmd && del install.cmd

Basic Usage

After installation, navigate to your project directory and launch Claude Code:

cd your-project
claude

Upon first use, you will be prompted to log in. Claude Code automatically keeps itself updated.

VS Code Extension Access

The Visual Studio Code extension provides a native graphical interface for Claude Code, integrating its capabilities directly into your IDE. This is the recommended way to use Claude Code within VS Code, offering a more visual and interactive experience.

Extension Installation

1. Open VS Code.
2. Press Cmd+Shift+X (Mac) or Ctrl+Shift+X (Windows/Linux) to open the Extensions view.
3. Search for "Claude Code" and click Install.

You may need to restart VS Code or run "Developer: Reload Window" from the Command Palette after installation.

Getting Started with the VS Code Extension

Once installed, you can start using Claude Code through the VS Code interface. The Spark icon indicates Claude Code throughout VS Code.

1. Open the Claude Code panel: Click the Spark icon in the Editor Toolbar (top-right corner of the editor) when a file is open. Alternatively, use the Command Palette (Cmd+Shift+P or Ctrl+Shift+P) and type "Claude Code".
2. Send a prompt: Ask Claude to assist with your code. You can select text in the editor and press Alt+K to insert an @-mention with the file path and line numbers directly into your prompt.
3. Review changes: When Claude proposes edits, it will show you a diff, allowing you to accept, reject, or modify the suggestions.

Switching to Terminal Mode within VS Code

If you prefer the CLI-style interface even within VS Code, you can switch the extension to terminal mode. Open VS Code settings (Cmd+, on Mac or Ctrl+, on Windows/Linux), go to Extensions > Claude Code, and check Use Terminal.

CLI vs. VS Code Extension: A Comparison

Feature/Aspect	Terminal (CLI)	VS Code Extension
Interface	Text-based, command-line	Graphical chat panel (default), integrated into IDE
Integration	System-wide, scriptable	Native VS Code integration, context-aware
Control	Full control over commands and scripting	Visual review of changes, inline diffs
Workflows	Ideal for automation, CI/CD, advanced scripting	Interactive development, visual feedback, easier navigation
Feature Parity	Has full feature set	May not have full feature parity with CLI (yet)
Shared History	Shares conversation history with extension	Shares conversation history with CLI

It is also possible to run the Claude Code CLI directly within VS Code's integrated terminal, combining the power of the CLI with the IDE's environment.

Understanding New Codebases

When joining a new project, Claude Code can quickly provide insights into the codebase structure and logic.

1. Navigate to project root: cd /path/to/project
2. Start Claude Code: claude
3. Ask for an overview: > give me an overview of this codebase
4. Dive deeper: > explain the main architecture patterns used here or > what are the key data models?

Fixing Bugs Efficiently

Claude Code can assist in identifying and fixing bugs by analyzing error messages and suggesting solutions.

1. Share the error: > I'm seeing an error when I run npm test
2. Ask for recommendations: > suggest a few ways to fix the @ts-ignore in user.ts
3. Apply the fix: > update user.ts to add the null check you suggested

Refactoring Code

Modernizing legacy code or improving code quality can be done with Claude Code's help.

1. Identify legacy code: > find deprecated API usage in our codebase
2. Get refactoring recommendations: > suggest how to refactor utils.js to use modern JavaScript features
3. Apply changes: > refactor utils.js to use ES2024 features while maintaining the same behavior

Working with Tests

Claude Code can help in generating tests for uncovered code and ensuring test coverage.

1. Identify untested code: > find functions in NotificationsService.swift that are not covered by tests
2. Generate test scaffolding: > add tests for the notification service
3. Add test cases: > add test cases for edge conditions in the notification service

Handling Documentation

Claude Code can assist in creating and updating documentation for your codebase.

1. Identify undocumented code: > find functions without proper JSDoc comments in the auth module
2. Generate documentation: > add JSDoc comments to the undocumented functions in auth.js

Creating Pull Requests

Claude Code can help summarize changes and generate well-documented pull requests.

1. Summarize changes: > summarize the changes I've made to the authentication module
2. Generate a PR: > create a pr

Plan Mode

Plan Mode allows Claude Code to create a detailed plan by analyzing the codebase with read-only operations. This is crucial for complex changes or code reviews, ensuring safety and thoroughness.

To start a new session in Plan Mode:

claude --permission-mode plan

Plan Mode is ideal for:

• Safely exploring and understanding complex codebases
• Creating detailed implementation plans before making changes
• Code reviews and architecture assessments
• Onboarding to new projects

Specialized Subagents

Claude Code can delegate tasks to specialized AI subagents for more effective assistance. You can view available subagents or create custom ones.

To view available subagents:

/agents

Subagents can be specialized for tasks like:

• Code review and quality checks
• Security vulnerability scanning
• Performance optimization suggestions
• Documentation generation

Model Context Protocol (MCP)

MCP extends Claude Code's capabilities by allowing it to integrate with external data sources, providing a richer context for its operations. Through MCP, Claude Code can:

• Pull information from Google Drive documents
• Access Figma designs for UI implementation
• Connect to Slack for team context
• Integrate with other external tools and services

Extended Thinking (Ultrathink)

For complex problems requiring deeper reasoning, Claude Code offers an "ultrathink" mode, allowing for more extensive analysis and problem-solving. This feature enables Claude to spend more time reasoning through difficult problems before providing solutions.

Use extended thinking for:

• Complex architectural decisions
• Multi-file refactoring planning
• Debugging intricate issues
• Performance optimization analysis

Conclusion

Claude Code is a powerful and versatile tool that can significantly enhance a developer's productivity. By understanding its features and how to access it through both the terminal and VS Code extension, you can leverage its capabilities for a wide range of coding tasks, from basic code understanding to complex refactoring and automation.

References

• Claude Code Docs. "Claude Code overview." https://code.claude.com/docs/en/overview
• Claude Code Docs. "Common workflows." https://code.claude.com/docs/en/common-workflows
• Claude Code Docs. "Use Claude Code in VS Code." https://code.claude.com/docs/en/vs-code