- Unix-like operating systems use commands, like the top command in Linux, to access many functions to which Windows or macOS would assign a graphical user interface.
- Learning the commands associated with Unix-like operating systems is crucial for maximizing your experience.
- The top command in Linux is used to open an interactive process monitoring window that displays usage statistics and a list of running processes.
- The top command can be customized with additional commands to perform various tasks, such as closing the process monitor, sending output to a file, and sorting processes by user.
Unix-like operating systems use commands, like the top command in Linux, to access many functions to which Windows or macOS would assign a graphical user interface. Thus, users of these operating systems are heavily encouraged to learn the commands associated with their operating system of choice.
Not learning these commands will severely hinder your ability to get the most out of your experience. Unix-like operating systems focus a lot less on providing a graphical user interface. They’re primarily designed for programmers and people experienced in code environments. Let’s assess the top command in Linux, what it is, and how to use it.
What Is the top Command in Linux?
You can use the “top” command in Linux to open an interactive process monitoring window, pictured below. The upper half of the window shows the usage statistics, while the lower shows a list of processes currently running.
The upper half of the top command window has five lines that display essential information about your computer’s performance. They are as follows:
|Physical memory usage
|Virtual memory usage
The process monitor has several columns containing essential data about your system’s processes and performance. They are as follows:
|The unique Process ID
|The process priority. A lower number in this column indicates higher priority in the system.
|The total virtual memory the process is currently using, updated in real-time.
|The name of the user running the process
|The total percentage of the CPU’s power the process is currently using, updated in real-time
|The CPU time represented through hundredths of a second. This is functionally the same as TIME but has more granularity since it clocks smaller increments.
|The shared memory size of a process in kilobytes.
|The Nice Value of the process. A negative number represents a higher priority.
|The total memory usage of the task
|The total physical RAM usage measured in kilobytes.
|The name of the command used to start the process
How Do I Execute the top Command?
To execute the top command, all you have to do is open the command line and enter “top” with no capitalization. It looks like this:
That’s it. However, you can execute additional commands with the top command to make it do extra things. Let’s examine those alternative prompts.
Close the Process Monitor
To close the process monitor, press the “q” key.
Automatically Close the Process Monitor
You can set the process monitor to close automatically after a certain number of iterations. To do that, you’ll want to enter the following into the command line:
top -n int
Enter a number for int, and the process monitor will automatically close after it refreshes that many times. If you don’t enter this, the program will continue to run and refresh until you manually close it with q.
Send the Output from top to a File
You can also send top’s output to a file of your choice using the batch command. To do that, enter the following into the command line:
top -b > output.txt
You can change the output to whatever you’d like; we just wanted it to be obvious how you were supposed to do everything.
Open the Process Monitor in Safe Mode
You can open the process monitor in safe mode using the following command:
Opening the process in safe mode will force it to use as few resources as possible and only the minimum required drivers. It will also force it to be a single-user instance rather than a multi-user instance.
Show the Processes Sorted by User
If you want to see what processes a specific user is running, you can do that by entering the following command:
top -u user
Replace “user” with the person’s username, and then the top command will show you what processes they’re running on the computer when you run it.
Show top Command Syntax
If you want to know the top command’s syntax, you can use the following command:
This will bring up the syntax for a wide variety of commands that you can execute alongside top.
Show the Delay Time Between Screen Updates
If you input the following command:
top -d seconds.tenths
It will have the process monitor display the delay between refreshes.
Open the Process Monitor in the Last Saved State
If you’ve got specific settings you want to maintain between your iterations of the process monitor, you open the program in the same state you last opened it in with the following command:
This command will maintain the state of your top command window between sessions. It will allow you to keep the settings and commands you opened alongside it functioning without entering them all individually.
Monitor Only Specific Processes
You can also monitor specific processes using the following command:
top -p PID1, PID2…
To use this command, you need to know the process PID already, but you can enter as many PIDs as you want to and monitor the usage statistics of just those processes.
Highlight Running Processes
Highlighting running processes can help you identify which ones are giving you trouble regarding usage statistics. While the process monitor is open, you can highlight running processes by pressing the “z” key. That will make any currently running programs appear in color, making them easier to find.
If you want to shut a process down from the monitor window, you can highlight the program you want to kill and press the “k” key.
Sort Programs by CPU Usage
If you’re trying to figure out what’s hogging your entire CPU, you can sort the process monitor by CPU usage. Press SHIFT + P while the window is open to sort it by use.
Change Display Units
You can change the units in which your process monitor displays usage by pressing the “e” key while the window is open. You can set the display unit to kibibytes, mebibytes, gibibytes, tebibytes, pebibytes, or exbibytes.
Toggle Usage Graphs
If you’d like to see a graphical representation of your usage statistics, you can toggle that by pressing the “t” key.
Show the Absolute Path of a Process
If you need to know where a process is running from, you can access its absolute path — the path from the root — by pressing the “c” key while the PID is highlighted.
Show Process Hierarchy
If you want to know which processes were opened or influenced by others, press the “v” key to open the process hierarchy.
Show Only Active Tasks
If you want the process monitor only to show active tasks, you can have it sort those to the top by pressing the “i” key.
Limit Process Number
If you only want to see the top few processes, you can limit the number of monitored scripts by pressing the “n” key. The top window will then prompt you to input the number of programs you want it to track. Input how many programs you want to see — such as the top 5, 10, etc. — and let it re-sort the information.
Change Process Priority
You can also change the priority the computer assigns to its running processes from the top command. Highlight the PID of the process you want to adjust and press the “r” key. The window will prompt you to enter a new Nice Value, which controls the priority.
The image featured at the top of this post is ©Zhanna Hapanovich/Shutterstock.com.