# rtop

**Author:** retoor <retoor@molodetz.nl>

A terminal-based system monitoring tool written in C that displays comprehensive system statistics in a dynamic, auto-refreshing interface. rtop is designed as a lightweight alternative to htop with no external dependencies beyond the standard C library.

## Features

- Real-time system monitoring with configurable refresh interval
- Per-core CPU utilization with temperature and frequency display
- Memory and swap usage statistics
- Process listing sorted by CPU or memory usage
- Network interface statistics with RX/TX rates
- Disk I/O statistics
- Filesystem usage information
- Color-coded output for utilization levels
- Terminal resize handling
- Keyboard controls (q to quit)

## Requirements

- Linux operating system
- GCC compiler (C99 compliant)
- Make build system

## Building

```bash
make
```

The build produces a single binary `rtop` with minimal dependencies.

### Build Options

```bash
make clean      # Remove build artifacts
make debug      # Build with debug symbols
make install    # Install to /usr/local/bin (requires root)
```

## Usage

```bash
./rtop [OPTIONS]

Options:
  -d, --delay SECS   Update interval in seconds (default: 1.0)
  -s, --sort MODE    Sort by: cpu (default), mem
  -h, --help         Show help message
  -v, --version      Show version
```

### Examples

```bash
./rtop              # Run with default settings
./rtop -d 2         # Update every 2 seconds
./rtop -s mem       # Sort processes by memory usage
```

## Display Sections

- **Header**: Hostname, OS version, kernel, uptime, load averages
- **CPU**: Per-core utilization, total usage, temperature, frequency
- **Memory**: RAM and swap usage with buffer/cache information
- **Processes**: Summary counts (running, sleeping, stopped, zombie)
- **Network**: Interface statistics with IP addresses and transfer rates
- **Disk I/O**: Read/write rates and IOPS per device
- **Filesystems**: Mount points with usage percentages
- **Process List**: Detailed per-process information

## Controls

- `q` or `Q`: Quit the application
- `Ctrl+C`: Terminate

## Technical Details

### Data Sources

All system information is read from the Linux `/proc` and `/sys` filesystems:

- `/proc/stat` - CPU statistics
- `/proc/meminfo` - Memory information
- `/proc/[pid]/stat` - Process information
- `/proc/net/dev` - Network statistics
- `/proc/diskstats` - Disk I/O statistics
- `/sys/class/thermal/` - Temperature sensors

### Performance

- Target CPU usage: <5%
- Startup time: <100ms
- Memory footprint: <10MB RSS
- Binary size: ~1.2MB

## Project Structure

```
rtop/
├── include/
│   ├── cpu.h
│   ├── disk.h
│   ├── display.h
│   ├── filesystem.h
│   ├── memory.h
│   ├── network.h
│   ├── process.h
│   ├── system.h
│   └── terminal.h
├── src/
│   ├── cpu.c
│   ├── disk.c
│   ├── display.c
│   ├── filesystem.c
│   ├── main.c
│   ├── memory.c
│   ├── network.c
│   ├── process.c
│   ├── system.c
│   └── terminal.c
├── Makefile
└── README.md
```

## License

This project is provided as-is for educational and personal use.