File Operations¶

Learn how Claude Code CLI reads, creates, and modifies files directly on your filesystem.

What You'll Learn¶

How Claude CLI reads files from disk
Creating new files in your terminal session
Editing existing files directly
Working with multiple files
Understanding the permission system

How the CLI Accesses Files¶

Unlike the Claude web interface where you copy/paste code, Claude Code CLI has direct filesystem access in your working directory. It uses specialized tools internally:

Tool	Purpose
Read	View file contents
Write	Create new files
Edit	Modify existing files
Glob	Find files by pattern
Grep	Search file contents

You don't call these directly - just describe what you want.

Reading Files¶

Single File¶

> Show me the contents of package.json

Claude reads and displays the file.

> What does the main function in src/index.js do?

Claude reads the file and explains it.

Multiple Files¶

> Compare config.dev.js and config.prod.js

Claude reads both and shows differences.

> Show me all the test files

Claude finds and summarizes test files.

Partial Reading¶

For large files:

> Show me the first 50 lines of server.js

> What's in the handleAuth function in auth.js?

Claude can focus on specific sections.

Creating Files¶

Simple Creation¶

> Create a file called hello.py that prints "Hello World"

Claude will: 1. Show you the proposed file content 2. Ask for permission to create it 3. Create the file

With Specifications¶

> Create a React component called Button with these props:
  - label (string)
  - onClick (function)
  - disabled (boolean, optional)

Claude generates appropriate code based on context.

Multiple Files¶

> Create a basic Express server with:
  - index.js (main server)
  - routes/api.js (API routes)
  - middleware/auth.js (auth middleware)

Claude creates the structure and files.

Editing Files¶

Direct Edits¶

> In utils.js, change the timeout from 5000 to 10000

Claude finds the line and makes the change.

Descriptive Edits¶

> Add error handling to the fetchUser function

Claude understands the function and adds appropriate try/catch.

Refactoring¶

> Rename the variable 'data' to 'userData' throughout auth.js

Claude updates all occurrences.

Adding to Files¶

> Add a new method called 'reset' to the Counter class

Claude finds the class and adds the method.

The Permission System¶

Claude asks before modifying your filesystem:

Claude wants to create file: src/utils/helpers.js

--- Proposed content ---
export function formatDate(date) {
  return date.toISOString().split('T')[0];
}
------------------------

Allow? (y/n/e)

Options: - y - Yes, make the change - n - No, don't make it - e - Edit the proposed change first

Trust Modes¶

For experienced users, you can adjust permissions:

> /config

# Set trust level for file operations

Practical Patterns¶

Pattern 1: Explore Then Edit¶

> Show me the config file

> Okay, change the port to 8080

Read first to understand context.

Pattern 2: Batch Operations¶

> Add TypeScript types to all functions in utils/

Claude processes multiple files.

Pattern 3: Find and Replace¶

> Find all uses of 'console.log' and replace with our logger

Claude searches and replaces across files.

Pattern 4: Template Creation¶

> Create a new component following the same pattern as UserCard.jsx

Claude reads the template and creates a similar file.

Working with Different File Types¶

Code Files¶

> Add JSDoc comments to all exported functions in api.js

Configuration¶

> Add a new script called "lint" to package.json that runs eslint

Documentation¶

> Update the README to include the new API endpoints

Data Files¶

> Add a new user to users.json with id 5, name "Alice"

Try It Yourself¶

Exercise: File Operations Practice¶

Create a practice directory:

mkdir file-practice && cd file-practice
claude

Create some files:

> Create a calculator.py with add, subtract, multiply, divide functions

Read and understand:
```
> Explain what calculator.py does
```

Make edits:

> Add a power function to calculator.py

> Add docstrings to all functions

Create related files:

> Create test_calculator.py with tests for each function

Verify your work:
```
> Show me both files side by side
```

Exercise: Refactoring¶

Ask Claude to create a messy file:

> Create a file called messy.js with a 50-line function that does
  too many things (fetch user, validate, format, save)

Refactor it:

> Refactor messy.js into smaller, focused functions

Compare:
```
> What improvements did we make?
```

Best Practices¶

Be Specific¶

# Vague
> Fix the file

# Specific
> In auth.js, the validateToken function returns undefined when
  the token is expired. It should throw an ExpiredTokenError instead.

Provide Context¶

> I'm using Express.js and MongoDB. Create a user registration
  endpoint that hashes passwords with bcrypt.

Verify Changes¶

> Show me what you changed in that last edit

Use Relative Paths¶

> Edit src/components/Header.jsx

Claude understands your project structure.

What's Next?¶

Now that you can work with files, learn how to prompt Claude effectively in 04-asking-questions.

Summary: - Claude reads files automatically when you reference them - Ask to create files, and Claude shows you what it'll write before doing it - Edit by describing what you want changed - no need for exact syntax - The permission system protects you from unwanted changes - Be specific about what files you mean and what changes you want

Learning Resources¶

Featured Video¶

NetworkChuck: AI in the Terminal - File Operations (3.6M subscribers)

Learn how Claude Code reads, creates, and modifies files directly on your filesystem with permission handling.

Additional Resources¶

Type	Resource	Description
🎬 Video	Claude Code File Editing Guide	All About AI - File operations deep dive
📚 Official Docs	Security & Permissions	File access controls documentation
📖 Tutorial	DataCamp File Operations	Refactoring and file editing examples
🎓 Free Course	Anthropic Academy	Official free courses
💼 Commercial	GitHub Copilot Course	AI file editing patterns