In our previous articles, we have discussed the basics of ls command and cat command. In this article, we are going to delve into the top command which is one of the most commonly used commands in our daily system administrative tasks.

The top command (table of processes) presents the processor activity of your Linux machine and also displays tasks managed by the kernel in real-time. Additionally, it provides details about CPU and memory usage for a list of running processes.

You might also find the following tutorials interesting :

• Htop – An Interactive Process Viewer for Linux
• Iotop – Monitor Linux Disk I/O Activity and Usage Per-Process Basis
• bmon – A Powerful Network Bandwidth Monitoring for Linux
• Find Top 15 Processes by Memory Usage in Linux

1. List All Running Linux Processes

To view all running Linux Processes, simply type top on the command line to get the information of active tasks, memory, cpu, and swap. Press ‘q‘ to exit the window.

<code><strong># top</strong></code>

2. Sort Linux Processes by PID

To sort all Linux active processes by Process ID, press M and T keys.

3. Sort Linux Processes by Memory and CPU Usage

To arrange all Linux running processes by Memory utilization, press M and P keys.

4. Sort Linux Processes by Execution Time

To organize all Linux running processes by their execution time, press M and T keys.

5. Display Linux Processes By Specific User

To display all user-specific active processes information, use the -u option which will list specific User process details.

<code><strong># top -u tecmint</strong></code>

6. Highlight Active Process in Top

Press ‘z‘ option will show the active process in color which may help you to identify the running process easily.

7. Show Absolute Path of Running Linux Processes

Press ‘c‘ option while the top command is running will display the absolute path of the active process.

8. Set Refresh Interval for Top Command

By default, the screen refresh interval is set to 3.0 seconds; you can adjust this by pressing the ‘d‘ option while running the top command to set your preferred interval time.

9. Terminate Running Linux Process Using Top Command

You can terminate a process after identifying its PID by pressing the ‘k‘ option while the top command is active without closing the top window as shown below.

10. Sort Linux Processes by CPU Utilisation

To sort all active processes by CPU utilization, simply press Shift P key.

11. Renice a Linux Process

You can utilize the ‘r‘ option to alter the priority of the process also referred to as Renice.

12. Check Linux CPU Cores

To view the load information of your CPU cores, simply press 1 to display the CPU core details.

13. Save Top Command Output in File

To save the output of the running top command results to a file /root/.toprc use the following command.

<code># top -n 1 -b > top-output.txt</code>

14. View Linux Idle Processes

Press 'i' to see the list of idle/sleeping processes.

15. Access Top Command Help

Press the ‘h‘ option to access the top command help.

16. Exit Top Command After Specific Iterations

The output of the top command keeps refreshing until you press ‘q‘. With the following command, it will automatically stop after 10 iterations.

<code><strong># top -n 10</strong></code>

There are numerous options available to learn more about the top command; you may refer to the man page of the top command. Please share this if you find this article helpful or leave your feedback using the comment section below.

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