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Codex Examples

πŸ“… 2026-06-22 | πŸ“‚ Codex

This section demonstrates various use cases of Codex CLI through practical examples to help you quickly master its application in real-world development.

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Code Writing

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Example 1: Creating New Features

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Have Codex create a complete feature module for you:

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Task

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Create a Python function that accepts a list of strings and returns the longest string and its index position

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Codex will generate code similar to the following:

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Generated Code

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def find_longest_string(strings):\\n    """\\n    Find the longest string in a List of strings and its Index position.\\n    \\n    Args:\\n        strings: List of strings\\n    \\n    Returns:\\n        tuple: (Longest string, Indexposition)\\n               If the list is empty, return (None, -1)\\n    """\\n    if not strings:\\n        return None, -1\\n    \\n    longest = max(strings, key=len)\\n    index = strings.index(longest)\\n    \\n    return longest, index\\n\\n# TestExample\\nif __name__ == "__main__":\\n    test_list = ["apple", "banana", "cherry", "dragonfruit"]\\n    result, idx = find_longest_string(test_list)\\n    print(f"Longest string: {result}, Index: {idx}")\\n    # Output: Longest string: dragonfruit, Index: 3\\n
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Codex-generated code includes detailed documentation comments and test examples, ready for immediate use.

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Example 2: Refactoring Code

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Request Codex to refactor existing code:

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Task

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Refactor this function to use a generator:

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def get_squares(n):\\n    result = []\\n    for i in range(n):\\n        result.append(i * i)\\n    return result\\n
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Codex will provide the refactored code:

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Refactored Code

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def get_squares(n):\\n    """\\n    Generate from 0 to n-1 square numbers of。\\n    \\n    Args:\\n        n: Count of generated square numbers\\n    \\n    Yields:\\n        int: 0 to n-1 square numbers of\\n    """\\n    for i in range(n):\\n        yield i * i\\n\\n# Usage example\\nfor square in get_squares(5):\\n    print(square)\\n# Output: 0, 1, 4, 9, 16\\n
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Code Review

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Example 1: Reviewing Code Issues

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Request Codex to review code and provide improvement suggestions:

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Task

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Review the issues in the following code:

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def process_data(data):\\n    result = []\\n    for item in data:\\n        if item['type'] == 'a':\\n            result.append(item['value'] * 2)\\n        elif item['type'] == 'b':\\n            result.append(item['value'] + 10)\\n        elif item['type'] == 'c':\\n            result.append(item['value'])\\n    return result\\n
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Codex will analyze and provide a review report:

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Code Review Report

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Issues

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  1. Missing error handling: No check whether item contains required keys
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  2. Inconsistent types: 'c' type returns the original value directly, while other types are processed
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  3. Hard-coded values: Multipliers and addends should be parameters or configurations
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Improvement Suggestions

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  1. Add default dictionary or try-except handling
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  2. Unify processing logic
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  3. Extract magic numbers as constants
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Example 2: Using the /review Command

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Use the built-in review command in Codex:

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Task

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/review src/\\n
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Codex will scan the entire src/ directory and generate a comprehensive code review report.

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Debugging and Troubleshooting

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Example 1: Analyzing Error Messages

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Give error messages to Codex for analysis:

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Task

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Help me analyze this error:

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Traceback (most recent call last):\\n  File "app.py", line 42, in <module>\\n    main()\\n  File "app.py", line 38, in fetch_data()\\n  File "app.py", line 25, in fetch_data\\n    response = requests.get(url)\\n  File "/usr/lib/python3.10/site-packages/requests/api.py", line 88, in in get\\n    return session.request(method='GET', url=url, **kwargs)\\nrequests.exceptions.ConnectionError: HTTPSConnectionPool(host='api.example.com', port=443): Max retries exceeded\\n
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Codex will provide analysis and solutions:

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Error Analysis

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Cause

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Network connection issue - unable to connect to api.example.com

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Possible Reasons

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  1. Network is unreachable
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  2. Domain name resolution failure
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  3. Server is unavailable
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  4. Firewall blocking
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Suggested Troubleshooting Steps

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  1. Check network connection: ping api.example.com
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  2. Verify domain resolution: nslookup api.example.com
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  3. Check if port is open: telnet api.example.com 443
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  4. If local development, check proxy settings
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Example 2: Adding Debug Logs

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Request Codex to add debug code:

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Task

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Add debug logs to this function:

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def calculate(a, b):\\n    return a + b * (a - b)\\n
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Codex will generate a version with debug logs:

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Adding Debug Logs

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import logging\\n\\n# Configure logging\\nlogging.basicConfig(level=logging.DEBUG)\\nlogger = logging.getLogger(__name__)\\n\\ndef calculate(a, b):\\n    """Calculation function with debug logs"""\\n    logger.debug(f"calculate called with a={a}, b={b}")\\n    \\n    result = a + b * (a - b)\\n    \\n    logger.debug(f"a + b = {a} + {b} = {a + b}")\\n    logger.debug(f"a - b = {a} - {b} = {a - b}")\\n    logger.debug(f"b * (a - b) = {b} * {a - b} = {b * (a - b)}")\\n    logger.debug(f"final result: {result}")\\n    \\n    return result\\n
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File Operations

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Example 1: Batch Renaming Files

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Task

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Rename all files like image_001.jpg in the current directory to image-001.jpg (replace underscores with hyphens)

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Example 2: Creating Project Structure

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Task

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Create a standard directory structure for a Flask project, including:

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  • app.py main file
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  • config.py configuration file
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  • requirements.txt
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  • tests/ directory
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  • static/ and templates/ directories
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Codex will create the complete project structure and generate all necessary files.

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Codex will first list the files to be created and execute after confirmation.

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Command Execution

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Example 1: Running Tests

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Task

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Run the project's unit tests

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Codex will automatically detect the project type and run the corresponding test commands:

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  • Python projects: pytest or unittest
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  • Node.js projects: npm test or yarn test
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  • Rust projects: cargo test
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Example 2: Git Operations

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Task

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Create a Git commit with all changes and an appropriate commit message

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Codex will analyze all uncommitted changes, then execute:

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  1. git status - view changes
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  2. git diff - review specific modifications
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  3. git add -A - add all files
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  4. git commit -m "..." - create commit
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For Git operations, Codex will first display the changes and execute after confirmation.

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Project Analysis

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Example 1: Understanding Project Structure

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Task

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Analyze this project's architecture and technology stack

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Codex will check the project's:

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  • Configuration files (package.json, Cargo.toml, requirements.txt, etc.)
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  • Directory structure
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  • Main source files
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Then provide a detailed analysis report.

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Example 2: Finding Dependencies

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Task

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Find which files reference auth.py

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Plan Mode

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Use the /plan command for planning complex tasks:

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Task

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/plan Add user authentication to this React project, including login, registration, and JWT verification\\n
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Codex will first display a detailed implementation plan:

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Implementation Plan: User Authentication Feature

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Step 1: Preparation

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  • Create user model
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  • Install authentication dependencies (jsonwebtoken, bcryptjs)
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Step 2: Backend Implementation

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  • Create /api/auth/register endpoint
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  • Create /api/auth/login endpoint
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  • Implement JWT generation and verification middleware
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Step 3: Frontend Implementation

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  • Create login form component
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  • Create registration form component
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  • Add authentication state management
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Step 4: Testing

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  • Write backend unit tests
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  • Test frontend form interactions
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Confirm execution of this plan?
\\n Confirm Cancel Modify

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Plan mode lets you understand Codex's complete thought process before execution, avoiding unnecessary rework.

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Comprehensive Example

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A complete workflow example:

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Complete Workflow

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# 1. Start new session\\n/new\\n\\n# 2. Understand the project\\nWhat framework does this project use? What are its main features?\\n\\n# 3. Add new feature\\nAdd a verification code sending feature to the users module, considering:\\n- Verification code generation (6 digits)\\n- 60 Cannot be resent within seconds\\n- Verification code valid for 10 minutes\\n\\n# 4. Test\\nRun relevant Tests to ensure proper functionality.\\n\\n# 5. Code review\\n/review\\n
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This example demonstrates a typical development workflow: understand project β†’ implement feature β†’ test β†’ review.

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Quick Operations Summary

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ScenarioCommand to Use
Write a functionDescribe requirements directly
Review code/review or "help me review..."
Debug issuesPaste error message and request analysis
Execute commandsStart with !
Complex task planning/plan + task description
Understand code"What does this function do?"
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Practice makes perfect. The more you use Codex, the more proficient you'll become, and your coding efficiency will improve significantly.

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