How to use the command `htop` (with examples)

htop is a powerful and interactive process viewer for Unix systems that offers a user-friendly interface to monitor system resources and running processes in real-time. It enhances the traditional top command by providing additional features such as a color-coded display, tree view of processes, sorting capabilities, and easy-to-use interactive controls. It is ideal for system administrators and developers who need to manage multiple processes and assess system performance efficiently.

Use case 1: Start htop

Code:

htop

Motivation for using this example: Simply running htop is the most basic use of the command and provides a gateway to exploring the tool’s features. By launching htop, users can quickly access a dynamic view of system processes and resource utilization, allowing them to identify the most resource-intensive processes at a glance.

Explanation:

• htop: This command starts the htop application, which opens up an interactive graphical interface displaying a list of current processes along with CPU, memory, and swap usage.

Example output: When you start htop, you’ll see a colorful screen featuring a list of processes running on your system, along with columns for CPU and memory usage, process ID, user, and process name. The top section shows bar-graph style visualizations of CPU and memory usage.

Use case 2: Start htop displaying processes owned by a specific user

Code:

htop --user username

Motivation for using this example: When monitoring system processes, it can be valuable to filter the display to show only tasks associated with a specific user. This option is particularly useful in multi-user environments, where you might want to assess the resources consumed by processes belonging to a specific user account.

Explanation:

• --user: This option filters the processes displayed to those owned by the specified user.
• username: Replace this placeholder with the actual username whose processes you wish to monitor.

Example output: Using this command restricts the list to only those processes owned by the specified user, allowing you to focus on user-specific activity without being overwhelmed by system processes or other users’ processes.

Use case 3: Display processes hierarchically in a tree view

Code:

htop --tree

Motivation for using this example: Visualizing processes in a tree format helps to understand the hierarchy and relationships between parent and child processes. This is crucial for diagnosing complex process interactions and ensuring that script-managed forks and process spawns are functioning as expected.

Explanation:

• --tree: This argument formats the process list in a tree view, showing the parent-child relationships between processes.

Example output: The output will depict processes in an indented list, illustrating which processes have spawned other processes. This hierarchical view provides insights into dependency chains and context for each process’s role within the system.

Use case 4: Sort processes by a specified sort item

Code:

htop --sort sort_item

Motivation for using this example: Being able to sort processes by specific criteria lets users focus on what matters most at a given moment. Whether it’s to identify the processes using the most CPU, memory, or to inspect the latest spawned processes, sorting helps in quickly pinpointing the priorities.

Explanation:

• --sort: Specifies that the processes should be sorted according to the given attribute.
• sort_item: The sorting criteria, such as cpu, mem, etc. It determines which column the processes should be sorted by.

Example output: If you sort by cpu, htop reorders the list, prioritizing those processes that are consuming the most CPU resources, allowing for a quick assessment of CPU load distribution.

Use case 5: Start htop with the specified delay between updates

Code:

htop --delay 50

Motivation for using this example: Adjusting the update delay between refresh cycles is important for conserving system resources on lower-powered machines or to gain a more stable view of process dynamics without rapid fluctuations.

Explanation:

• --delay: Adjusts the interval between screen updates in tenths of a second.
• 50: Specifies a 5-second interval, giving a balance between resource usage and update speed.

Example output: Screen updates now happen every 5 seconds, offering a more static view that allows for detailed observation of longer-term trends without the need for fine-grained real-time monitoring.

Use case 6: See interactive commands while running htop

Code:

?

Motivation for using this example: While familiarizing yourself with htop or if you ever forget a key binding, accessing the interactive command list can significantly enhance your efficiency and enable you to make full use of htop’s capabilities.

Explanation:

• ?: A shortcut key pressed during htop’s execution that displays a list of interactive commands and their associated keybindings.

Example output: A help screen overlays with a comprehensive list of key bindings and the functions they perform, aiding both new and experienced users in leveraging htop effectively.

Use case 7: Switch to a different tab

Code:

tab

Motivation for using this example: Navigating through various tabs in htop helps you view different sets of data, such as different sorting criteria or additional system information, all without restarting or exiting the application.

Explanation:

• tab: A key press that cycles through available tabs in htop, each representing a different organizational view or dataset.

Example output: Switching tabs might shift the view to a different sorting parameter or could show cumulative data instead of per-process data, depending on your preset configurations.

Use case 8: Display help

Code:

htop --help

Motivation for using this example: Reviewing the help guide directly within the terminal ensures that users have access to full-feature documentation and command options, especially when working offline, or without quick access to external documentation.

Explanation:

• --help: Outputs a condensed manual directly to the terminal, listing usage options, explanations, and examples.

Example output: The terminal displays a concise manual page for htop, detailing every available command-line option and argument to use with it, enhancing understanding and broadening the tool’s utilization.

Conclusion:

The htop command offers a rich set of functionalities that make process monitoring both accessible and powerful. By exploring its various use cases, users can tailor htop to meet their specific needs—whether it’s focusing on memory usage, sorting processes by different criteria, or helping identify process hierarchies. With continued practice, you can become adept at managing and analyzing the intricate dynamics of your system processes using htop.