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 /proc filesystem. It is one of the important utilities for system administration specifically under process monitoring, to help you understand whats is going on 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 in the ps man page.
List All Processes in Current Shell
1. If you run ps command without any arguments, it displays processes for the current shell.
1 | $ ps |
List Current Running Processes
Print All Processes in Different Formats
2. Display every active process on a Linux system in generic (Unix/Linux) format.
1 | $ ps -A |
List Processes in Standard Format
3. Display all processes in BSD format.
1 | $ ps au |
List Processes in BSD Format
4. To perform a full-format listing, add the -f or -F flag.
1 | $ ps -ef |
List Processes in Long List Format
Display User Running Processes
5. You can select all processes owned by you (runner of the ps command, root in this case), type:
1 | $ ps -x |
6. To display a user’s processes by real user ID (RUID) or name, use the -U flag.
1 | $ ps -fU tecmint |
List User Processes by ID
7. To select a user’s processes by effective user ID (EUID) or name, use the -u option.
1 | $ ps -fu tecmint |
Print All Processes Running as Root (Real and Effecitve ID)
8. The command below enables you to view every process running with root user privileges (real & effective ID) in user format.
1 | $ ps -U root -u root |
Display Root User Running Processes
Display Group Processes
9. If you want to list all processes owned by a certain group (real group ID (RGID) or name), type.
1 | $ ps -fG apache |
Display Group Processes
10. To list all processes owned by effective group name (or session), type.
1 | $ ps -fg apache |
Display Processes by PID and PPID
11. You can list processes by PID as follows.
1 | $ ps -fp 1178 |
List Processes by PID
12. To select process by PPID, type.
1 | $ ps -f --ppid 1154 |
List Process by PPID
13. Make selection using PID list.
1 | $ ps -fp 2226,1154,1146 |
List Processes by PIDs
Display Processes by TTY
14. To select processes by tty, use the -t flag as follows.
1 | $ ps -t pst/0 |
List Processes by TTY
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).
1 | $ ps -e --forest |
List Process Tree
16. You can also print a process tree for a given process like this.
1 | $ ps -f --forest -C sshd |
List Tree View of Process
Print Process Threads
17. To print all threads of a process, use the -H flag, this will show the LWP (light weight process) as well as NLWP (number of light weight process) columns.
1 | $ ps -fL -C httpd |
List Process Threads
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.
1 | $ ps L |
19. The command below allows you to view the PID, PPID, user name and command of a process.
1 | $ ps -eo pid,ppid,user,cmd |
List Processes with Names
20. Below is another example of a custom output format showing file system group, nice value, start time and elapsed time of a process.
1 | $ ps -p 1154 -o pid,ppid,fgroup,ni,lstart,etime |
List Process ID Information
21. To find a process name using its PID.
1 | $ ps -p 1154 -o comm= |
Find Process using PID
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.
1 | $ ps -C sshd |
Find Parent Child Process
23. Find all PIDs of all instances of a process, useful when writing scripts that need to read PIDs from a std output or file.
1 | $ ps -C httpd -o pid= |
Find All Process PIDs
24. Check execution time of a process.
1 | $ ps -eo comm,etime,user | grep httpd |
The output below shows the HTTPD service has been running for 1 hours, 48 minutes and 17 seconds.
Find Process Uptime
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.
1 | $ ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head |
Find Top Running Processes
27. To kill an Linux processes/unresponsive applications or any process that is consuming high CPU time.
First, find the PID of the unresponsive process or application.
1 | $ ps -A | grep -i stress |
Then use the kill command to terminate it immediately.
1 | $ kill -9 2583 2584 |
Find and Kill a Process
Print Security Information
28. Show security context (specifically for SELinux) like this.
1 | $ ps -eM |
Find SELinux Context
29. You can also display security information in user-defined format with this command.
1 | $ ps -eo euser,ruser,suser,fuser,f,comm,label |
List SELinux Context by Users
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).
1 | $ watch -n 1 'ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head' |
Real Time Process Monitoring
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 tool.