🎯 Overview

The OpenTTY file system is a virtual file system that provides a unified interface to access different types of storage resources within the J2ME environment. It combines RMS storage, device file systems, virtual directories, and temporary storage into a single hierarchical structure.

🗂️ File System Structure

📍 Root Directories

/
├── /home/          # 📝 RMS Record Stores (User Files)
├── /tmp/           # 🗑️ Temporary In-Memory Storage
├── /mnt/           # 💾 Device File System (JSR-75)
├── /bin/           # ⚡ Executable Scripts & Applications
├── /lib/           # 📚 Library Packages
├── /dev/           # 🔧 Special Devices
└── /res/           # 📦 Resource Files (JAR Resources)

🔧 Directory Details

🏠 /home/ - User Storage

• Storage: RMS Record Stores
• Permissions: Read/Write for current user
• Features:
  • Persistent storage across sessions
  • File management via RecordStore API
  • User-specific data storage

🗑️ /tmp/ - Temporary Storage

• Storage: In-memory Hashtable
• Permissions: Read/Write
• Features:
  • Volatile storage (lost on exit)
  • Fast access for temporary files
  • Session-specific data

💾 /mnt/ - Device File System

• Storage: JSR-75 FileConnection API
• Permissions: Device-dependent
• Features:
  • Access to device file system
  • Directory listing and file operations
  • Cross-platform file access

⚡ /bin/ - Executables

• Storage: Packaged scripts in RMS
• Permissions: Read-only (root can modify)
• Features:
  • Shell commands and scripts
  • Auto-execution via classpath
  • System utilities

📚 /lib/ - Libraries

• Storage: Packaged libraries in RMS
• Permissions: Read-only (root can modify)
• Features:
  • Shared packages and modules
  • Function libraries
  • Extension packages

🔧 /dev/ - Special Devices

• Virtual Devices:
  • stdin - Command input field
  • stdout - Output display
  • null - Empty device
  • random - Random number generator
  • zero - Zero byte source
  • tty - Terminal source

🛠️ File Operations

📋 Listing Files

ls /home/          # List user files
ls /mnt/           # List device roots
dir                # GUI file browser

📄 Reading Files

cat /home/notes.txt     # Read RMS file
cat /mnt/root/file.txt  # Read device file
cat /tmp/buffer         # Read temporary file

✏️ Writing Files

install /home/script.sh         # Install from nano buffer
touch /tmp/tempfile             # Create temporary file

🗑️ Deleting Files

rm /home/oldfile.txt    # Delete RMS record
rm /mnt/file.txt       # Delete device file
rm /tmp/tempfile       # Remove temporary file

🔐 Permissions Model

👤 User Types

• Root (id=0): Full system access
• Regular User (id=1000): Limited access

🔒 Permission Rules

• /home/: User can read/write their own files
• /tmp/: User can read/write all files
• /mnt/: Device-dependent permissions
• /bin/, /lib/: Read-only for users, writable by root
• System files: Read-only for all users

🎮 Special Features

📁 Virtual Directories

• Mount System: Create virtual directories via configuration
• Path Resolution: Automatic path completion
• Directory Stack: pushd/popd for navigation

🔄 File Types & Detection

• Automatic MIME type detection
• File extension mapping
• Binary vs Text classification

💽 Storage Management

• RMS Compression: Multiple files in single RecordStore
• Memory Management: Automatic garbage collection
• Storage Quotas: Configurable limits

🚀 Usage Examples

🔍 Basic Navigation

pwd                    # Show current directory
cd /home/              # Change to home directory
ls -a                  # List all files (including hidden)

📊 File Information

file /home/document.txt    # Get file type information
wc /home/script.sh         # Count lines, words, characters
du /mnt/file.txt          # Get file size

🔄 Advanced Operations

cp /home/source.txt /tmp/copy.txt    # Copy files
mount /home/filesystem.conf          # Mount virtual directories
rmsfix swap /bin/ /home/backup/      # Backup system files

⚠️ Limitations

• J2ME Constraints: Limited by device capabilities
• Storage Size: RMS storage limitations apply
• File Size: Memory constraints for large files
• Permissions: Device security restrictions

The OpenTTY file system provides a Unix-like experience within J2ME constraints, enabling powerful file management capabilities on mobile devices!