PyShell 🐚

A Bash-like Unix shell implemented in Python

PyShell is a lightweight Unix-style shell written in Python that mimics core Bash behavior.
It supports built-in commands, pipelines, redirection, environment variable expansion, command history with persistence, and tab completion using GNU Readline.

This project was built as a systems-level learning exercise, inspired by the Codecrafters Shell Challenge.

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✨ Features

🧠 Shell Core

• Command parsing with shlex
• Execution of external commands via subprocess
• Built-in command support
• Environment variable expansion ($VAR, ${VAR})

🔗 Pipelines & Redirection

• Pipes (|)
• Input redirection (<)
• Output redirection (>, >>)
• File descriptor redirection (1>, 2>)

📜 History Management (Bash-like)

• Persistent command history across sessions
• HISTFILE environment variable support
• Built-in history command with:
  • history – show history
  • history -a [file] – append new commands
  • history -r [file] – read history from file
  • history -w [file] – write history to file
  • history -c – clear in-memory history
• Correct incremental append behavior (no duplicates)

⌨️ User Experience

• Tab completion for:
  • Built-in commands
  • Executables in $PATH
  • Files and directories
• Command auto-completion display
• Interactive prompt ($ )

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🛠 Built-in Commands

Command	Description
cd	Change directory
pwd	Print current directory
echo	Print arguments
type	Identify command type
history	Manage command history
exit	Exit the shell

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🚀 How to Run

Requirements

• Linux (tested on Ubuntu)
• Python 3.8+
• GNU Readline

Run the shell

python3 main.py