The Linux top (table of process) command is a useful way to track information about your computer’s resource usage and the running processes’ in the background. Even with it’s basic interface, it can also support color, highlighting and even some basic graphs.
Top command gives users a dashboard of different processes and other system metrics. This information that is provided by top is useful for a system administrator as it helps track down problems before they emerge.
At the start of using top, the interface may seem off-putting and all-up-in-your-face, but that can easily be changed so that you can choose which display would suit your needs.
Prerequisites
Launch the terminal using the Ctrl+Alt+T key combination.
Accessing the Default Display
First, to start, type in top and hit “enter” to access the default view of the command.
Once you input the top command, the default display should look something like this:
Here you can see that in the upper part of the display, it shows the statistics about the process and storage usage of your computer. The lower half of the display shows the list of programs that are currently running. To navigate the display, simply use the arrow keys or page up and down keys.
Press “Q” to quit the window.
top Command Syntax and Option
1. Help Option
This function helps you access the help menu option to see the various key functions and shortcuts to use when navigating the dashboard. Some versions of Linux might have different shortcut commands for certain keys, so be sure to check the help option first.
press “H” to access the command help file
2. Changing the Numeric Units
Press capital “E” to cycle through units used to display memory values kibibytes, mebibytes, gibibytes, tebibytes, pebibytes, and exbibytes. If you want to track specific memory usage, this is a helpful way of doing it.
By pressing “E” you can see on the picture that the MiB changed to GiB.
3. Changing the Summary Contents
press “I” to toggle on or off the log summary line.
Pressing “T” once, you can swap the CPU display to simple ASCII graphs.
If you press “T” again, the graph display changes into solid block characters. Solid block characters will give a rough estimate of how much of your CPU is being used depending on the available resources.
By pressing “T” once more, you can remove the CPU display and task summary line completely. You can do this in order to keep your current display neat and tidy once you are done checking the CPU display and task summary line.
Pressing “M” would change the memory display to an ASCII graph.
When you press “M” again, it turns the memory display to solid block characters.
By pressing “M” again, you can remove the memory display line.
3. Changing the Color and Highlighting
press “Z” in order to add color to the display.
You can toggle which color preference you want from red or white displays.
By default, the process list is sorted by the % CPU column. You can change it by pressing “P” for the % CPU column. Pressing “M” for the % MEM column. Pressing “N” for the PID column. Then by pressing “T” for the TIME+ column.
Pressing “Y” will highlight the running tasks in the process list. Pressing “X” will highlight the column used to sort the process list. Then if you press “B” you can then toggle between bold and reverse text.
The picture above shows the selected TIME+ column.
4. Display Active Tasks
when you press “i” you can choose to only display the active tasks. Tracking which active tasks are running will be able to help you diagnose your system if you ever come across a problem like a program using too much memory causing your system to slow down.
5. Changing the priority of a process
press “R” to display the PID to renice.
You will then be prompted for the PID as seen in the picture above. The value of “7800” happened to be the PID of Firefox.
In the picture above, you need to assign the new nice value to apply to the process. As you can see, I typed 10. After you press “enter” the new nice value is applied to the process immediately.
6. Killing a Process
press “K” to kill a process. After pressing “K” you will be prompted to type the PID that you want to kill.
After pressing “enter” you will be offered the option to type the signal you want to send. If you leave it blank and hit “enter” again, top sends the SIGTERM(kill) signal.
The article should have guided you to the basic functions and options on how to use the top command. Make sure you always have the latest version of Ubuntu in order to follow the guide. In case of any more questions, feel free to comment them down below.
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