c-sysmon

An interactive terminal-based system monitor for Linux, written in C using ncurses.

Features

• Real-time System Monitoring

  • CPU usage with visual progress bar
  • Memory usage with visual progress bar
  • System load average (1, 5, and 15 minutes)
  • Live process list with detailed information

• Process Management

  • Sortable process list (by PID, CPU, Memory, or Name)
  • Display process state, CPU%, memory%, and nice values
  • Scroll through process list with keyboard

• User Interface

  • Clean ncurses-based terminal UI
  • Color-coded metrics (green/yellow/red based on usage)
  • Keyboard navigation and controls
  • Configurable refresh intervals

Architecture

The project follows a modular design with clear separation of concerns:

• sysinfo.c/h: Data collection module - reads from /proc filesystem
• ui.c/h: UI rendering module - handles ncurses display and user interaction
• main.c: Main program - coordinates data collection and UI updates

Requirements

• Linux operating system
• GCC compiler
• ncurses library

Installing ncurses

On Ubuntu/Debian:

sudo apt-get install libncurses5-dev libncursesw5-dev

On Fedora/RHEL/CentOS:

sudo dnf install ncurses-devel

On Arch Linux:

sudo pacman -S ncurses

Building

make

This will compile the source files and create the sysmon executable.

To clean build artifacts:

make clean

Installation

To install system-wide:

sudo make install

This installs the binary to /usr/local/bin/sysmon.

To uninstall:

sudo make uninstall

Usage

Run the system monitor:

./sysmon

Or if installed system-wide:

sysmon

Command Line Options

• -h, --help: Display help message
• -i, --interval SECONDS: Set refresh interval (default: 2 seconds)

Example with custom refresh interval:

./sysmon -i 5

Keyboard Controls

• q: Quit the program
• ↑/↓: Scroll through process list
• PgUp/PgDn: Page up/down in process list
• p: Sort by PID (ascending)
• c: Sort by CPU usage (descending)
• m: Sort by Memory usage (descending)
• n: Sort by process Name (ascending)
• r: Reverse current sort order

Display Information

Header Section

• CPU: Current CPU usage percentage with visual bar
• MEM: Memory usage percentage, visual bar, and used/total memory in MB
• Load: System load average for 1, 5, and 15 minutes
• Processes: Total number of running processes
• Sort: Current sort mode and direction

Process List

Each process shows:

• PID: Process ID
• NAME: Process name (truncated to 25 characters)
• STATE: Process state (R=Running, S=Sleeping, Z=Zombie, etc.)
• CPU%: CPU usage percentage
• MEM%: Memory usage percentage
• MEM(KB): Memory usage in kilobytes
• NICE: Process nice value (priority)

Technical Details

• Reads CPU statistics from /proc/stat
• Reads memory information from /proc/meminfo
• Reads load average from /proc/loadavg
• Reads process information from /proc/[pid]/stat and /proc/[pid]/status
• Uses ncurses for terminal UI with color support
• Implements efficient process sorting algorithms
• Calculates CPU percentages based on time differences between samples

License

See LICENSE file for details.