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# CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
## Project Overview
**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.
## Development Commands
```bash
# Development (Zig)
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
# Legacy (Original Rust - archived)
cargo run # Run in debug mode with REPL shell
cargo build # Build debug version
```
## Instructions
Always run the `zig fmt` to format source code after every change. Example:
```
find . -name \*.zig -exec 'zig' 'fmt' '{}' ';'
```
## Architecture
### Command System Design
The application uses a type-safe command architecture with Zig unions and enums:
- **`Command`**: Top-level union supporting pipes, redirections, external programs, and builtins
- **`BuiltinCommand`**: Comprehensive DOS command set covering file operations, shell control, and utilities
- **`FileSpec`**: Handles console (`Con`) vs file path targets for I/O redirection
- **`InputSource`**: Manages input redirection from files with line-by-line processing
- **`OutputCapture`**: Buffers command output for redirection to files
### Implementation Status
#### ✅ **Fully Implemented Features**
- **Interactive REPL Shell**: Command-line interface with DOS-style prompts (`C:\PATH>`)
- **Command Parsing**: Complete lexer/parser for DOS command syntax with quote support
- **Built-in Commands**: Core DOS commands with authentic behavior and error messages
- **External Command Execution**: Full process spawning with I/O redirection support
- **I/O Redirection**: Complete input (`<`), output (`>`), and append (`>>`) redirection
- **Error Handling**: DOS-authentic error messages and proper exit codes
- **Path Formatting**: DOS-style path display with drive letters and 8.3 filename conversion
#### 📋 **Built-in Commands Available**
- **`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
- **`DIR`** - Directory listing with file sizes and counts
- **`TYPE`** - Display file contents with binary character filtering
- **`SORT`** - Alphabetical line sorting with input redirection support
#### 🔧 **External Command Support**
- **Process Spawning**: Uses `std.process.Child` for external program execution
- **Argument Passing**: Proper command-line argument handling
- **I/O Redirection**: Full stdin/stdout/stderr redirection support
- **Error Handling**: DOS-compatible "command not found" messages
- **Exit Code Propagation**: Proper process exit code handling
#### 🔀 **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
### Key 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
#### **Cross-Platform Support**
- **Zig Standard Library**: Portable file system and process operations
- **ANSI Terminal Support**: Cross-platform terminal manipulation
- **Path Handling**: DOS-style path formatting on all platforms
### Dependencies
**Zero External Dependencies** - The Zig implementation uses only the standard library:
- **`std.process`**: External command execution and process management
- **`std.fs`**: File system operations for I/O redirection and DIR command
- **`std.mem`**: Memory management and string operations
- **`std.time`**: System time access for DATE/TIME commands
- **`std.io`**: Terminal I/O and file operations
### Build Configuration
The project uses Zig's standard build system with optimizations:
- **Debug builds**: Full error checking and memory leak detection
- **Release builds**: Size and speed optimized for production use
- **Cross-compilation**: Native Zig cross-platform compilation support
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