1. Overview
The Linux top command is a very powerful tool for monitoring system performance. It helps when checking the system load and utilization and this can prevent a lot of issues. For example, we can analyze the behavior of different processes, detect bottlenecks, and make decisions based on this information.
In this tutorial, we’ll see a simple usage of the top command and learn how to manipulate its output format to be more human-readable.
2. Using the top Command
The top command by default provides an interactive output that lists the running processes and their respective CPU and memory usage. It automatically refreshes the output and updates the values periodically as they change. This gives the user visibility into the system’s performance and resource consumption.
One of the advantages of top utility is that it’s fairly straightforward to use:
$ top
top - 14:54:31 up 1 min, 1 user, load average: 1.76, 2.17, 2.27
Tasks: 12 total, 1 running, 11 sleeping, 0 stopped, 0 zombie
%Cpu(s): 5.6 us, 3.8 sy, 0.0 ni, 89.5 id, 0.1 wa, 0.0 hi, 1.0 si, 0.0 st
MiB Mem : 96570.6 total, 16933.1 free, 18452.3 used, 61185.2 buff/cache
MiB Swap: 0.0 total, 0.0 free, 0.0 used. 77278.0 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 165220 10520 8244 S 0.0 0.0 0:00.16 systemd
256 root 20 0 16132 7812 6844 S 0.0 0.0 0:00.04 systemd-journal
561 systemd+ 20 0 25252 12460 8520 S 0.0 0.0 0:00.11 systemd-resolve
1122 root 20 0 14896 6512 5708 S 0.0 0.0 0:00.07 systemd-logind
2197 root 20 0 9468 5940 3808 S 0.0 0.0 0:00.01 bash
2380 root 20 0 10616 3772 3196 R 0.0 0.0 0:00.00 top Here, the output is divided into two parts:
- upper part: dashboard
- lower part: task list
The dashboard displays in the first five rows a summary of some system information:
- system uptime
- total number of processes
- average CPU usage
- average memory utilization
So, the dashboard provides an overview that we can quickly look at.
On the other hand, the task list provides a breakdown of the processes and their respective resource consumption. Thus, we’re able to monitor performance and track activity with finer detail.
3. top Human-Readable Format
The default output of top shows sizes in the Kibibyte unit, so it might not be easy to interpret. However, we can change this default format by pressing the e key while on the main screen:
$ top
top - 05:37:45 up 10 min, 1 user, load average: 4.39, 3.08, 2.41
Tasks: 12 total, 1 running, 11 sleeping, 0 stopped, 0 zombie
%Cpu(s): 8.0 us, 1.7 sy, 0.0 ni, 89.8 id, 0.0 wa, 0.0 hi, 0.6 si, 0.0 st
MiB Mem : 96570.6 total, 10829.5 free, 12615.3 used, 73125.8 buff/cache
MiB Swap: 0.0 total, 0.0 free, 0.0 used. 83024.8 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 161.3m 10.3m 8.0m S 0.0 0.0 0:00.15 systemd
257 root 20 0 15.8m 7.8m 6.8m S 0.0 0.0 0:00.04 systemd-journal
561 systemd+ 20 0 24.7m 12.3m 8.5m S 0.0 0.0 0:00.11 systemd-resolve
1123 root 20 0 14.5m 6.3m 5.5m S 0.0 0.0 0:00.07 systemd-logind
2194 root 20 0 9.2m 5.7m 3.6m S 0.0 0.0 0:00.01 bash
2386 root 20 0 10.4m 3.7m 3.2m R 0.0 0.0 0:00.00 topHere, we used the top command and then pressed e while on the screen. Consequently, we see sizes in the task list area are in Mebibyte. Depending on the components, this is usually a more convenient format for humans.
Since the dashboard area is still in the KiB format, we can convert it into MiB by pressing the Shift+e key combination on the main screen:
top - 05:38:31 up 11 min, 1 user, load average: 2.47, 2.74, 2.32
Tasks: 12 total, 1 running, 11 sleeping, 0 stopped, 0 zombie
%Cpu(s): 6.4 us, 2.8 sy, 0.0 ni, 90.0 id, 0.1 wa, 0.0 hi, 0.6 si, 0.0 st
GiB Mem : 94.3 total, 10.0 free, 12.8 used, 71.5 buff/cache
GiB Swap: 0.0 total, 0.0 free, 0.0 used. 80.6 avail Mem As we can see, the output format of the dashboard is now adjusted. We can keep changing the unit of the format between KiB, MiB, GiB, and so on, by pressing e for the task area and Shift+E for the dashboard area.
Finally, we can save the configuration of the output display by pressing W. This enables us to later use the command with the current configured state.
4. Conclusion
In this article, we’ve discussed the basics of using top and learned how to format its output to be more user-friendly.
In summary, top is a command-line utility to monitor system performance and resource utilization. It provides a comprehensive output with information about the overall system as well as a breakdown of each individual process.
The default output of the command shows sizes in KiB format. However, we can modify this by pressing the e or Shift+E keys. The lowercase e modifies the output in the task area, while the Shift+E modifies it in the dashboard area.