catrilao / shell-python

Custom Python shell implementing basic commands and external program execution

Python Shell Implementation

This project is part of the "Build Your Own Shell" Challenge by Codecrafters. Through this challenge, I’ve explored the fundamentals of Unix-like shell environments and implemented various features to bring this shell to life.

Project Overview

In this project, I've developed a basic shell that can handle built-in commands such as cd, echo, pwd, type, and also execute external programs found in the system’s PATH. Here are some of the key capabilities and features I’ve added:

• Built-in Commands: Support for essential shell commands.
• External Program Execution: Running external binaries and scripts.
• Command History: Maintaining a session's command history and enabling auto-completion.
• Error Handling: Graceful handling of various error scenarios to ensure smooth operation.

Features I Implemented

1. Command History and Auto-completion:

   • I set up command history using Python's readline module.
   • Implemented auto-completion for commands, making the shell more user-friendly.

2. Built-in Commands:

   • echo: Prints the provided arguments.
   • pwd: Displays the current working directory.
   • cd: Changes the working directory.
   • type: Checks if a command is built-in or an external executable.
   • exit: Exits the shell and saves the command history.

3. External Program Execution:

   • My shell can search for and execute external programs, similar to how traditional shells operate.

4. Robust Error Handling:

   • Implemented comprehensive error handling for file operations and command executions to provide meaningful feedback to the user.

How to Use This Shell

Prerequisites

• Python 3.11+.

Running the Shell

1. Clone the Repository:

   git clone https://github.com/catrilao/shell-python.git
   cd shell-python

2. Start the Shell:

   ./your_shell.sh

3. Try It Out: Once the shell is running, you can enter commands as you would in any terminal. Here are some commands you can try:

   $ echo "Hello world!"
   $ pwd
   $ cd /some/directory
   $ type ls
   $ ls -la
   $ exit

Example Commands

• echo Hello, World!: Prints Hello, World!.
• pwd: Shows the current working directory.
• cd ~: Changes to the home directory.
• type ls: Checks if ls is a built-in command or an external program.
• exit: Exits the shell and saves the command history.

Development Process

This project has been a fantastic learning experience. I’ve enjoyed diving into the internals of shell operations and translating those concepts into Python code. Here’s a brief overview of how I developed and tested each feature:

1. Initial Setup:

   • Started by setting up a basic loop to read and execute commands.
   • Implemented support for simple built-in commands.

2. Adding Functionality:

   • Expanded support to handle external commands using Python’s subprocess module.
   • Enhanced the shell with command history and auto-completion.

3. Robust Error Handling:

   • Added comprehensive error handling to provide clear feedback and maintain smooth operation.

4. Testing and Refinement:

   • Manually tested each feature to ensure proper functionality.
   • Refined command parsing and error messages for better user experience.

Acknowledgments

• Codecrafters: Thanks to Codecrafters for providing the "Build Your Own Shell" challenge. It has been instrumental in enhancing my skills in shell environments and Python programming.