Look at all processes linux

30 Useful ‘ps Command’ Examples for Linux Process Monitoring

ps (processes status) is a native Unix/Linux utility for viewing information concerning a selection of running processes on a system: it reads this information from the virtual files in the /proc filesystem. It is one of the important utilities for system administration specifically under process monitoring, to help you understand whats is going on in a Linux system.

It has numerous options for manipulating its output, however, you’ll find a small number of them practically useful for daily usage.

In this article, we’ll look at 30 useful examples of ps commands for monitoring active running processes on a Linux system.

Note that ps produces output with a heading line, which represents the meaning of each column of information, you can find the meaning of all the labels on the ps man page.

List All Processes in Current Shell

1. If you run the ps command without any arguments, it displays processes for the current shell.

Print All Processes in Different Formats

2. Display every active process on a Linux system in generic (Unix/Linux) format.

3. Display all processes in BSD format.

4. To perform a full-format listing, add the -f or -F flag.

Display User Running Processes

5. You can select all processes owned by you (runner of the ps command, root in this case), type:

6. To display a user’s processes by real user ID (RUID) or name, use the -U flag.

$ ps -fU tecmint OR $ ps -fu 1000

7. To select a user’s processes by effective user ID (EUID) or name, use the -u option.

$ ps -fu tecmint OR $ ps -fu 1000

Print All Processes Running as Root (Real and Effective ID)

8. The command below enables you to view every process running with root user privileges (real & effective ID) in user format.

Display Group Processes

9. If you want to list all processes owned by a certain group (real group ID (RGID) or name), type.

$ ps -fG apache OR $ ps -fG 48

10. To list all processes owned by effective group name (or session), type.

Display Processes by PID and PPID

11. You can list processes by PID as follows.

12. To select process by PPID, type.

13. Make a selection using a PID list.

Display Processes by TTY

14. To select processes by tty, use the -t flag as follows.

$ ps -t pts/0 $ ps -t pts/1 $ ps -ft tty1

Print Process Tree

15. A process tree shows how processes on the system are linked to each other; processes whose parents have been killed are adopted by the init (or systemd).

16. You can also print a process tree for a given process like this.

$ ps -f --forest -C sshd OR $ ps -ef --forest | grep -v grep | grep sshd

Print Process Threads

17. To print all threads of a process, use the -L flag, this will show the LWP (lightweight process) as well as NLWP (number of the lightweight processes) columns.

Specify Custom Output Format

Using the -o or –format options, ps allows you to build user-defined output formats as shown below.

18. To list all format specifiers, include the L flag.

19. The command below allows you to view the PID, PPID, user name, and command of a process.

20. Below is another example of a custom output format showing file system group, nice value, start time, and elapsed time of a process.

$ ps -p 1154 -o pid,ppid,fgroup,ni,lstart,etime

Display Parent and Child Processes

22. To select a specific process by its name, use the -C flag, this will also display all its child processes.

23. Find all PIDs of all instances of a process, useful when writing scripts that need to read PIDs from an std output or file.

24. Check the execution time of a process.

$ ps -eo comm,etime,user | grep httpd

The output below shows the HTTPD service has been running for 1 hour, 48 minutes, and 17 seconds.

Troubleshoot Linux System Performance

If your system isn’t working as it should be, for instance, if it’s unusually slow, you can perform some system troubleshooting as follows.

26. Find top running processes by highest memory and CPU usage in Linux.

$ ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head OR $ ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%cpu | head

27. To kill Linux processes/unresponsive applications or any process that is consuming high CPU time.

First, find the PID of the unresponsive process or application.

Then use the kill command to terminate it immediately.

Print Security Information

28. Show security context (specifically for SELinux) like this.

29. You can also display security information in a user-defined format with this command.

$ ps -eo euser,ruser,suser,fuser,f,comm,label

Perform Real-time Process Monitoring Using Watch Utility

30. Finally, since ps displays static information, you can employ the watch utility to perform real-time process monitoring with repetitive output, displayed after every second as in the command below (specify a custom ps command to achieve your objective).

$ watch -n 1 'ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head'

Important: ps only shows static information, to view frequently updated output you can use tools such as htop; top, and glances: the last two are in fact Linux system performance monitoring tools.

You might also like to read the following related articles.

That’s all for now. If you have any useful ps command example(s) to share (not forgetting to explain what it does), use the comment form below.

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Linux List Processes – How to Check Running Processes

Bolaji Ayodeji

Every day, developers use various applications and run commands in the terminal. These applications can include a browser, code editor, terminal, video conferencing app, or music player.

For each of these software applications that you open or commands you run, it creates a process or task.

One beautiful feature of the Linux operating system and of modern computers in general is that they provide support for multitasking. So multiple programs can run at the same time.

Have you ever wondered how you can check all the programs running on your machine? Then this article is for you, as I’ll show you how to list, manage, and kill all the running processes on your Linux machine.

Prerequisites

• A Linux distro installed.
• Basic knowledge of navigating around the command-line.
• A smile on your face 🙂

A Quick Introduction to Linux Processes

A process is an instance of a running computer program that you can find in a software application or command.

For example, if you open your Visual Studio Code editor, that creates a process which will only stop (or die) once you terminate or close the Visual Studio Code application.

Likewise, when you run a command in the terminal (like curl ifconfig.me ), it creates a process that will only stop when the command finishes executing or is terminated.

How to List Running Processes in Linux using the ps Command

You can list running processes using the ps command (ps means process status). The ps command displays your currently running processes in real-time.

To test this, just open your terminal and run the ps command like so:

This will display the process for the current shell with four columns:

• PID returns the unique process ID
• TTY returns the terminal type you’re logged into
• TIME returns the total amount of CPU usage
• CMD returns the name of the command that launched the process.

You can choose to display a certain set of processes by using any combination of options (like -A -a , -C , -c , -d , -E , -e , -u , -X , -x , and others).

If you specify more than one of these options, then all processes which are matched by at least one of the given options will be displayed.

Type man ps in your terminal to read the manual for the ps command, which has a complete reference for all options and their uses.

To display all running processes for all users on your machine, including their usernames, and to show processes not attached to your terminal, you can use the command below:

Here’s a breakdown of the command:

• ps : is the process status command.
• a : displays information about other users’ processes as well as your own.
• u : displays the processes belonging to the specified usernames.
• x : includes processes that do not have a controlling terminal.

This will display the process for the current shell with eleven columns:

• USER returns the username of the user running the process
• PID returns the unique process ID
• %CPU returns the percentage of CPU usage
• %MEM returns the percentage memory usage
• VSV returns the virtual size in Kbytes
• RSS returns the resident set size
• TT returns the control terminal name
• STAT returns the symbolic process state
• STARTED returns the time started
• CMD returns the command that launched the process.

How to List Running Processes in Linux using the top and htop Commands

You can also use the top task manager command in Linux to see a real-time sorted list of top processes that use the most memory or CPU.

Type top in your terminal and you’ll get a result like the one you see in the screenshot below:

An alternative to top is htop which provides an interactive system-monitor to view and manage processes. It also displays a real-time sorted list of processes based on their CPU usage, and you can easily search, filter, and kill running processes.

htop is not installed on Linux by default, so you need to install it using the command below or download the binaries for your preferred Linux distro.

sudo apt update && sudo apt install htop

Just type htop in your terminal and you’ll get a result like the one you see in the screenshot below:

How to Kill Running Processes in Linux

Killing a process means that you terminate a running application or command. You can kill a process by running the kill command with the process ID or the pkill command with the process name like so:

To find the process ID of a running process, you can use the pgrep command followed by the name of the process like so:

To kill the iTerm2 process in the screenshot above, we will use any of the commands below. This will automatically terminate and close the iTerm2 process (application).

Conclusion

When you list running processes, it is usually a long and clustered list. You can pipe it through less to display the command output one page at a time in your terminal like so:

or display only a specific process that matches a particular name like so:

I hope that you now understand what Linux processes are and how to manage them using the ps , top , and htop commands.

Make sure to check out the manual for each command by running man ps , man top , or man htop respectively. The manual includes a comprehensive reference you can check if you need any more help at any point.

Thanks for reading – cheers! 💙

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