# Dose - DOS-Style Command Shell

**Dose** is a DOS-style command shell implementation written in Zig. Originally started in Rust, the project has been completely rewritten in Zig to provide a nostalgic DOS computing experience with modern systems programming capabilities.

This project faithfully reproduces classic MS-DOS command behaviors, syntax, and error messages while running on modern systems.

## Features

### Interactive REPL Shell
- DOS-style command prompt (`C:\PATH>`)
- Complete lexer/parser for DOS command syntax with quote support
- Authentic DOS behavior and error messages

### Built-in Commands

**Core File Operations:**
- **`COPY`** - File copying with overwrite prompts and device handling
- **`DIR`** - Directory listing with file sizes, counts, and free space display
- **`TYPE`** - Display file contents with binary character filtering
- **`CD/CHDIR`** - Directory navigation with path validation

**Extended File Operations:**
- **`MD/MKDIR`** - Directory creation with nested path support
- **`RD/RMDIR`** - Directory removal with safety checks
- **`REN/RENAME`** - File and directory renaming
- **`DEL/REMOVE`** - File deletion with wildcard support
- **`PATH`** - Environment PATH variable management (GET/SET)
- **`MOVE`** - File/directory moving (placeholder)

**Shell and System Commands:**
- **`ECHO`** (with ON/OFF variants) - Text output and echo state control
- **`CLS`** - Clear screen with ANSI escape sequences
- **`EXIT`** - Exit the shell
- **`VER`** - Version information display
- **`DATE`** - Current system date with proper calendar calculations
- **`TIME`** - Current system time display
- **`SORT`** - Alphabetical line sorting with input redirection support

### I/O Redirection System
- **Input redirection** (`<`): Read file content as command input
- **Output redirection** (`>`): Write command output to file (overwrite)
- **Append redirection** (`>>`): Append command output to file
- **Combined redirection**: Support for both input and output redirection simultaneously
- **Device handling**: Proper CON/LPT/PRN device recognition and error handling

### External Command Support
- Full process spawning with I/O redirection support
- Proper command-line argument handling
- DOS-compatible "command not found" messages
- Exit code propagation

### Path Formatting
- DOS-style path display with drive letters
- 8.3 filename conversion where applicable
- Converts `/` to `\` and uppercases drive letters and names
- Defaults to `C:` when no drive is present

## Technical Features

### Memory Management
- **Allocator-based**: Uses Zig's `GeneralPurposeAllocator` for all dynamic memory
- **RAII Pattern**: Proper resource cleanup with `defer` statements
- **Leak Detection**: Built-in memory leak detection in debug builds

### Error Handling
- **Zig Error Unions**: Native `!T` error handling instead of exceptions
- **DOS-Authentic Messages**: Faithful reproduction of classic DOS error text
- **Graceful Degradation**: Robust error recovery and user guidance

### Architecture
- **Type-Safe Commands**: Uses Zig unions and enums for command architecture
- **Modular Design**: Clean separation between parsing, execution, and I/O
- **Zero Dependencies**: Uses only Zig standard library
- **Cross-Platform**: Portable file system and process operations

## Build

Requirements:
- Zig (recent version)

Commands:
```bash
# Development
zig build                 # Build debug version
zig build run             # Build and run in debug mode
zig build test            # Run unit tests
zig build -Doptimize=ReleaseFast  # Optimized build
```

This produces an executable in `zig-out/bin/dose`.

## Run

Start the shell:

```
zig-out/bin/dose
```

You’ll see a DOS-like prompt. Example interactions:

```
C:\> VER
DOSE Version 6.22
C:\> DIR
... directory listing ...
C:\> COPY CON hello.txt
Hello world! 
^Z
 1 File(s) copied
C:\> TYPE hello.txt
Hello world!
```

Redirection:

```
C:\> DIR > dir.txt
C:\> TYPE dir.txt
```

Change directory:

```
C:\> CD ..
C:\> DIR
```

## Project Structure

```
src/
├── cmd/                    # Modular command implementations
│   ├── lib/
│   │   └── types.zig      # Shared command types and interfaces
│   ├── chdir.zig          # CD/CHDIR command
│   ├── cls.zig            # CLS command  
│   ├── copy.zig           # COPY command
│   ├── date.zig           # DATE command
│   ├── dir.zig            # DIR command
│   ├── echo.zig           # ECHO command variants
│   ├── mkdir.zig          # MD/MKDIR command
│   ├── move.zig           # MOVE command (placeholder)
│   ├── path.zig           # PATH command (GET/SET)
│   ├── remove.zig         # DEL/REMOVE command
│   ├── rename.zig         # REN/RENAME command
│   ├── rmdir.zig          # RD/RMDIR command
│   ├── sort.zig           # SORT command
│   ├── time.zig           # TIME command
│   └── type.zig           # TYPE command
├── cmd.zig                # Command type definitions and imports
├── eval.zig               # Command execution engine
├── parser.zig             # DOS command line parser
├── paths.zig              # DOS path formatting utilities  
├── syntax.zig             # Command syntax structures
└── main.zig               # Application entry point and REPL
```

## License

GNU AGPLv3.