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.