What is htop and How to Use It

This article provides an overview of htop, an interactive, real-time system monitor and process viewer designed for Unix-like operating systems. You will learn what htop is, how it improves upon the traditional top command, its key features, and how to use it to monitor and manage system resources like CPU, memory, and running processes.

Understanding htop

Historically, Unix and Linux systems have used the top command-line utility to monitor system resources. While functional, top provides a basic, text-heavy interface that can be difficult to navigate.

Developed as an advanced alternative, htop is an interactive, text-mode process viewer. It displays a frequently updated list of the processes running on a computer, normally ordered by the amount of CPU usage. Unlike top, htop provides a full list of processes running, instead of just the top resource-consuming ones. For detailed configuration options and advanced usage, you can consult the htop command line tool documentation.

Key Features of htop

  • Visual Resource Bars: At the top of the htop interface, you get a color-coded, graphical representation of CPU usage (for individual cores), memory usage, and swap space. This makes it easy to diagnose resource bottlenecks at a glance.
  • Interactive Controls: Users can scroll vertically to view the complete process list and horizontally to see full command lines.
  • Easy Process Management: You can kill, stop, or change the priority (renice) of processes directly from the interface using keyboard shortcuts, without needing to manually type the Process ID (PID).
  • Mouse Support: htop supports mouse clicks, allowing you to select processes, sort columns, and click menu buttons at the bottom of the screen.
  • Tree View: By pressing F5, you can view processes in a parent-child hierarchical tree, making it easy to see which application spawned a specific background process.

How to Install and Run htop

htop is not always pre-installed by default, but it is available in the official repositories of almost all Linux distributions.

To install htop on Debian/Ubuntu-based systems, run:

sudo apt update && sudo apt install htop

To install htop on RHEL/CentOS/Fedora systems, run:

sudo dnf install htop

Once installed, simply type htop in your terminal to launch the interface.

Essential Keyboard Shortcuts

Once htop is running, you can navigate and control your system using these primary shortcuts:

  • F3 or /: Search for a specific process by name.
  • F4: Filter the process list to show only matching processes.
  • F5: Toggle between the sorted list view and the hierarchical tree view.
  • F6: Sort processes by columns such as CPU%, MEM%, PID, or User.
  • F9: Kill a selected process by sending a signal (like SIGKILL or SIGTERM).
  • F10 or q: Quit the htop interface.