This is a starting point for Python solutions to the "Build Your Own Shell" Challenge.

In this challenge, you'll build your own POSIX compliant shell that's capable of interpreting shell commands, running external programs and builtin commands like cd, pwd, echo and more. Along the way, you'll learn about shell command parsing, REPLs, builtin commands, and more.

Note: If you're viewing this repo on GitHub, head over to codecrafters.io to try the challenge.

Passing the first stage

The entry point for your shell implementation is in app/main.py. Study and uncomment the relevant code, and push your changes to pass the first stage:

git commit -am "pass 1st stage" # any msg
git push origin master

Time to move on to the next stage!

Python Shell Implementation

A basic Unix shell implementation in Python that supports executing external programs with arguments and built-in commands.

Features

• Command Execution: Runs external programs with arguments
• PATH Resolution: Finds executables in system PATH
• Built-in Commands:
  • exit [code]: Exit the shell with optional status code
  • echo [args...]: Print arguments to stdout
  • type [command]: Display command type information

Implementation Details

Process Management

• Uses fork() and execvp() for command execution
• Parent process waits for child completion using waitpid()
• Proper exit status handling

Command Resolution

• Primary resolution using shutil.which()
• Fallback to manual PATH search
• Validates file existence and executable permissions

Code Structure

def find_executable(command)
    # Finds executable in PATH using shutil.which or manual search

def execute_command(command_parts)
    # Handles external command execution using fork/exec

def parse_command(command)
    # Parses input and handles built-in/external commands

Usage

Run the shell:

$ python app/main.py

Example commands:

$ echo Hello World
$ /bin/ls -l
$ type echo
$ exit 0

Error Handling

• Command not found
• Execution failures
• Invalid permissions
• Keyboard interrupts (Ctrl+C)
• EOF (Ctrl+D)

Requirements

• Python 3.8+
• Unix-like operating system (macOS, Linux)

Stage 2 & beyond

Note: This section is for stages 2 and beyond.

1. Ensure you have python (3.13) installed locally
2. Run ./your_program.sh to run your program, which is implemented in app/main.py.
3. Commit your changes and run git push origin master to submit your solution to CodeCrafters. Test output will be streamed to your terminal.