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🐚 Crash Shell Wiki

Welcome to the Crash Shell Wiki — a detailed guide to understanding, using, and extending your Rust-based modular shell. This is your go-to documentation for development, architecture, feature behavior, and contribution.

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📘 Overview

Crash Shell is a minimalist Unix-like shell written in Rust. It supports command execution, built-in commands like cd, pwd, and export, and offers an interactive prompt with command history via rustyline.

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🧱 Architecture

Crash Shell follows a clean, modular structure:

src/
├── shell/
│   ├── mod.rs         # Shell runner and coordinator
│   ├── builtins.rs    # Built-in command logic
│   ├── interface.rs   # User prompt + command history (rustyline)
│   └── state.rs       # Shell state (cwd, previous dir, env)
├── command/
│   ├── parser.rs      # Tokenizes and interprets input
│   └── executor.rs    # Runs external commands via std::process
├── utils.rs           # Variable and tilde expansion
├── main.rs            # Entry point

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⚙️ Built-in Commands

Crash Shell includes essential built-ins handled directly in builtins.rs:

Command	Description
cd [path]	Change current directory
cd -	Switch to previous directory
pwd	Print current working directory
export VAR=value	Set environment variable in the current shell
exit	Exit the shell

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💡 Environment Variable Expansion

Crash Shell supports:

• ~ expansion to home directory
• $VAR and ${VAR} lookup via std::env
• export VAR=value to define runtime env vars

Expansion happens in utils.rs and is automatically applied to arguments during parsing.

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🧠 Command History

• Powered by rustyline
• Arrow key navigation for history (↑/↓)
• History saved to .crash_history
• Prompt is built dynamically using the current working directory

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🔮 Planned Features

Feature ideas under consideration or development:

Feature	Description
alias	Define shortcut names for command strings
Redirection	Handle >, >>, < for file IO
Piping	Connect commands with `
Background Jobs	Run commands with &
Config File	Support ~/.crashrc to load aliases/env on start
Tab Completion	Autocomplete commands, paths, variables

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🛠 Development Notes

• You can run the shell with cargo run
• The main input loop is in shell/mod.rs
• Built-ins are matched by name in builtins.rs
• Any unrecognized command is passed to the system via executor.rs

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📚 How to Add a New Built-in

1. Open shell/builtins.rs
2. Add a new match arm in handle_builtin():

"mycommand" => {
    // your logic here
    true
}

3. Update the README and wiki (here) if it's user-facing.

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Happy hacking! 🐚🚀

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