Windows Task Manager Clone

A command-line Windows Task Manager clone built in Rust using raw Win32 API calls. This project demonstrates OS-level process management without relying on high-level abstractions.

Features

• Process Enumeration: Lists all running processes with detailed information
• Real-time CPU Monitoring: Per-process and system-wide CPU usage
• Memory Statistics: Working set memory usage per process and system totals
• Disk I/O Tracking: Read/write bytes for each process
• Thread Count: Number of threads per process
• Priority Management: View and modify process priority levels
• Interactive Controls: Navigate, sort, filter, and kill processes
• Color-Coded Display: CPU usage is color-coded for quick identification
• Kill Confirmation: Safety dialog before terminating processes

Requirements

• Operating System: Windows 10/11
• Rust: 1.70+ (2021 edition)
• Build Tools: MSYS2 with MinGW-w64 or Visual Studio Build Tools

Dependencies

Crate	Version	Purpose
windows	0.58	Win32 API bindings
crossterm	0.28	Terminal UI rendering

Building

Option 1: Using MSYS2 (MinGW-w64)

# Set up PATH for MSYS2
$env:PATH = "C:\msys64\ucrt64\bin;C:\msys64\usr\bin;$env:PATH"

# Build release version
cargo build --release

Option 2: Using Visual Studio Build Tools

# Ensure MSVC toolchain is installed
rustup default stable-msvc

# Build release version
cargo build --release

Output

The compiled binary will be at:

target\release\task_manager_clone.exe

Usage

.\target\release\task_manager_clone.exe

Keyboard Controls

Key	Action
q	Quit application
Ctrl+C	Quit application
↑ / ↓	Navigate process list
PgUp / PgDown	Scroll by page
Home / End	Jump to start/end
k	Kill selected process (with confirmation)
Y / N	Confirm/cancel kill
+ / =	Raise process priority
- / _	Lower process priority
s	Cycle sort column
r	Reverse sort order
/	Enter filter mode
Esc	Clear filter / Cancel

Sort Columns

Press s to cycle through:

1. CPU% - CPU usage percentage
2. Memory - Working set memory
3. Name - Process name (alphabetical)
4. PID - Process ID
5. Priority - Process priority class
6. Threads - Thread count
7. Disk Read - Total bytes read
8. Disk Write - Total bytes written

Press r to toggle ascending/descending order.

Filtering

1. Press / to enter filter mode
2. Type process name (case-insensitive)
3. Press Enter to apply or Esc to cancel
4. Press Esc again to clear the filter

Project Structure

task-manager/
├── Cargo.toml              # Project dependencies
├── README.md               # This file
└── src/
    ├── main.rs             # Entry point & event loop
    ├── app/
    │   ├── mod.rs          # Application state & logic
    │   ├── process_entry.rs # Process data structure
    │   └── sort.rs         # Sorting options
    ├── ui/
    │   ├── mod.rs          # UI module exports
    │   └── render.rs       # Terminal rendering
    ├── ffi/
    │   ├── mod.rs          # FFI module exports
    │   └── handles.rs      # RAII handle wrappers
    └── system/
        ├── mod.rs          # System module exports
        ├── processes.rs    # Process enumeration
        ├── memory.rs       # Memory metrics
        ├── cpu.rs          # CPU tracking
        ├── disk.rs         # Disk I/O stats
        └── priority.rs     # Priority management

Technical Details

Win32 APIs Used

Module	API	Purpose
Process Enumeration	CreateToolhelp32Snapshot	Create snapshot of processes
	Process32FirstW / Process32NextW	Iterate through processes
CPU Metrics	GetSystemTimes	System-wide CPU times
	GetProcessTimes	Per-process CPU times
Memory Metrics	GlobalMemoryStatusEx	System memory info
	GetProcessMemoryInfo	Per-process memory
Disk I/O	GetProcessIoCounters	Read/write byte counts
Priority	GetPriorityClass	Get process priority
	SetPriorityClass	Modify process priority
Process Control	OpenProcess	Get process handle
	TerminateProcess	Kill a process
	CloseHandle	Release handles

CPU Calculation Method

CPU percentage is calculated using time deltas between refresh intervals:

                    Process Time Delta
CPU % = ────────────────────────────────── × 100
                    System Time Delta

Where:

• Process Time Delta = (Kernel + User time) change for the process
• System Time Delta = (Kernel + User time) change for the system

This matches Windows Task Manager's calculation method, showing 0-100% regardless of core count.

Memory Metrics

Metric	Description
Working Set	Physical memory currently in use by the process
System Memory	Total and available physical RAM
Memory Load %	Percentage of physical memory in use

Priority Levels

Priority	Value	Description
Idle	4	Runs only when CPU is idle
Below Normal	6	Lower than normal priority
Normal	8	Default priority
Above Normal	10	Higher than normal priority
High	13	Significantly elevated priority
Realtime	24	Highest priority (dangerous!)

⚠️ Warning: Setting Realtime priority can freeze the system by starving critical OS processes.

Disk I/O

• Disk Read: Cumulative bytes read since process start
• Disk Write: Cumulative bytes written since process start

These are total values, not rates. Long-running processes will show higher values.

Thread Count

Shows the number of execution threads in each process. Limits depend on:

• Stack size (default 1 MB per thread)
• Available memory
• 32-bit processes: ~2000 threads max
• 64-bit processes: ~100,000+ threads max

Display

Column Layout

PID      Priority  Threads     Memory   CPU%   Disk Read  Disk Write  Name

Color Coding (CPU)

Color	CPU Usage
🟢 Green	< 20%
🔵 Cyan	20-50%
🟡 Yellow	50-80%
🔴 Red	≥ 80%

Status Bar

• Shows error messages and status updates
• Kill confirmation dialog appears here
• Help text with available commands

Safe Rust Wrappers

All Win32 API calls use unsafe blocks wrapped in safe Rust abstractions:

// RAII handle wrapper - automatically calls CloseHandle on drop
pub struct SnapshotHandle(HANDLE);

impl Drop for SnapshotHandle {
    fn drop(&mut self) {
        unsafe { CloseHandle(self.0); }
    }
}

This ensures:

• Handles are always properly closed
• Memory safety is maintained
• No resource leaks

Error Handling

• Failed API calls display error messages in the status bar
• Inaccessible processes (system processes) show 0% CPU and 0 bytes
• The application continues running even if individual process queries fail

Refresh Rate

• Default: 5 seconds
• Configurable via REFRESH_INTERVAL_MS constant in main.rs

Bookmarks

• Win32 API Index: https://learn.microsoft.com/en-us/windows/win32/apiindex/windows-api-list
• Process & Thread Reference: https://learn.microsoft.com/en-us/windows/win32/procthread/process-and-thread-reference
• windows-rs Docs: https://microsoft.github.io/windows-docs-rs/
• windows-rs GitHub: https://github.com/microsoft/windows-rs

Limitations

1. Elevated Processes: Cannot query CPU/memory for some system processes without admin rights
2. Disk I/O: Shows cumulative totals, not real-time rates
3. 32-bit Processes: Cannot query 64-bit process details from 32-bit build

License

MIT License - See LICENSE file for details.

Author

Created for OS Lab Project - Operating Systems Course

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Built with ❤️ using Rust and raw Win32 APIs