gsh

gsh is a lightweight, custom shell implemented from scratch in Go. It provides a simple REPL (Read-Eval-Print Loop) to execute commands, handle input/output, and spawn processes, aiming to give developers a clear understanding of shell internals while offering a functional CLI environment.

Features

• Custom Command Parser: Built-in tokenizer and parser for command processing
• Built-in Commands: Essential shell commands implemented natively
  • echo - Display text
  • pwd - Print working directory
  • cd - Change directory
  • ls - List directory contents
  • clear - Clear the terminal screen
  • whoami - Display current user
  • help - Show available commands
  • exit - Exit the shell
• External Command Execution: Execute system commands from /bin/
• Configurable Environment: Customizable prompt, theme, and color mode
• Command History: Track command history throughout the session
• Environment Variables: Manage shell environment variables
• Color Support: Optional colored output for enhanced user experience

Prerequisites

• Go 1.25.1 or higher
• Linux/Unix-based operating system

Installation

From Source

# Clone the repository
git clone <repository-url>
cd gsh

# Build the project
go build -o bin/gsh cmd/gsh/main.go

# Run the shell
./bin/gsh

Using Go Install

go install cmd/gsh/main.go

Usage

Start the shell by running:

./bin/gsh

You'll be greeted with a prompt that shows your current directory:

/home/user/workspace
gsh> 

Project Structure

gsh/
├── cmd/
│   └── gsh/
│       └── main.go           # Entry point
├── internal/
│   ├── builtins/             # Built-in command implementations
│   │   ├── builtins.go       # Command registry
│   │   ├── cd.go
│   │   ├── clear.go
│   │   ├── echo.go
│   │   ├── exit.go
│   │   ├── help.go
│   │   ├── ls.go
│   │   ├── pwd.go
│   │   └── whoami.go
│   ├── command/              # Command parsing
│   │   ├── command.go
│   │   └── parser.go
│   ├── config/               # Configuration management
│   │   ├── config.go
│   │   └── deafult.go
│   └── shell/                # Core shell implementation
│       ├── deafult.go
│       ├── repl.go           # REPL loop
│       └── shell.go          # Shell structure
├── plugins/                  # Plugin system (extensible)
├── bin/                      # Compiled binaries
├── go.mod                    # Go module definition
└── README.md

Configuration

The shell can be configured through the Config structure:

type Config struct {
    Prompt      string    // Custom prompt string
    Theme       string    // Color theme
    ColorMode   bool      // Enable/disable colors
    HistoryFile string    // Command history file path
}

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/Feature)
3. Commit your changes (git commit -m 'Add some Feature')
4. Push to the branch (git push origin feature/Feature)
5. Open a Pull Request

License

This project is licensed under the GNU General Public License v3.0 - see the LICENSE file for details.

Roadmap

• Plugin system implementation
• Command piping support (|)
• Input/Output redirection (>, <, >>)
• Background job execution (&)
• Tab completion
• Advanced history management with search
• Configuration file support
• Alias support
• Scripting capabilities

Acknowledgments

• Inspired by traditional Unix shells (bash, zsh, sh)
• Built as an educational project to understand shell internals