htop Command: Tutorial & Examples

Monitoring system resources

The htop command is an interactive process viewer, similar to the top command but with a more user-friendly interface and additional features. It not only shows the basic system information such as CPU usage, memory usage, and load averages, but also provides a real-time, colorful, easy-to-read overview of your system's running processes.

This command is widely used by system administrators to monitor system performance, diagnose high load issues, and even kill troublesome processes if needed.

How htop Works

In a nutshell, htop gathers information from the /proc directory and presents it in a human-readable format. The /proc directory is a virtual filesystem in Linux that provides process and kernel information to userspace.

Why htop is Important

htop offers several advantages over traditional top command:

• htop provides a full list of processes running, instead of the top resource-consuming processes.
• It allows for scrolling the list vertically and horizontally to see all processes and complete command lines.
• In 'htop' you don’t need to remember process IDs to kill a process, you can simply scroll to select a process, then press the F9 key.
• htop supports mouse operation, top doesn't.

Examples of Using htop

To start using htop, you simply need to type htop at the shell prompt. Here are some examples of how to use htop.

htop

This command will start htop on your terminal.

htop -u username

This command will filter the process list to include only those owned by the specified user.

htop -p 123,456,789

This command will monitor only the processes with the specified process IDs.

Understanding htop Output

The htop output is divided into three sections:

• The first section provides statistics about your system, like the usage of CPU, Memory, and Swap.
• The second section contains a list of all the processes running on your system.
• The third section has a footer menu with options that you can use to manage processes, filter the list, or exit the program.

Here's an example of what htop output might look like:

1  [|||||||                                  17.2%]     Tasks: 33, 57 thr; 2 running
2  [||||||||                                20.2%]     Load average: 0.08 0.02 0.01 
Mem[|||||||||||||||||||||||||||||   972M/3.86G]     Uptime: 00:11:22
Swp[                                        0K/0K]

PID USER      PRI  NI  VIRT   RES   SHR S CPU% MEM%   TIME+  Command            
1084 alan       20   0  657M  5372  3848 R  6.2  0.1  0:00.18 htop

Conclusion

The htop command is an excellent tool for monitoring system resources and managing processes. Its user-friendly interface and robust features make it an essential tool for every Linux system administrator. Take the time to get familiar with htop and it will make your life a whole lot easier when you need to diagnose and resolve performance-related issues.