Ps and pstree

This article describes the purpose of the Unix-tools ps and pstree. Furthermore, the most important options as well as their functions are presented.

Information

ps (process status) is an unix-command that displays an overview of all processes running on the system and its status. pstree (process tree) represents graphically the hierarchy of the processes in a tree topology. A comparable tool under Windows would be tasklist.exe.

Installation

The programs ps and pstree are normally contained in the default settings of the different Linux distributions. Otherwise, they can be installed via following packages:
procps for ps
psmisc for pstree

Meaning of the columns displayed

• UID = ID of the user that has started this process
• PID = clear process-ID
• STIME = time, when the process was started
• TTY = states the terminal, on which the process is running
• TIME = total system time used by the process
• CMD = name of the program that has started the process

Example of screen output

• extract from ps without options:

benutzer:~$ ps
  PID TTY          TIME CMD
 2897 pts/1    00:00:00 bash
 2914 pts/1    00:00:00 ps

• excerpt from pstree:

benutzer:~$ pstree
init─┬─/usr/lib/glippe
     ├─NetworkManager─┬─dhclient
     │                └─{NetworkManager}
     ├─acpid
     ├─atd
     ├─avahi-daemon───avahi-daemon
     ├─bluetoothd
     ├─bonobo-activati───{bonobo-activat}
     ├─clock-applet
     ├─console-kit-dae───63*[{console-kit-da}]
     ├─cron
[...]

Important options and its functions

All of the options listed below can be combined with each other to limit or extend the output to what is necessary!

• listing of all processes

 ps -e 

• displaying of extended information

 ps -f 

Example:

benutzer:~$ ps -ef
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 08:09 ?        00:00:01 /sbin/init
root         2     0  0 08:09 ?        00:00:00 [kthreadd]
root         3     2  0 08:09 ?        00:00:00 [migration/0]
root         4     2  0 08:09 ?        00:00:00 [ksoftirqd/0]
root         5     2  0 08:09 ?        00:00:00 [watchdog/0]
root         6     2  0 08:09 ?        00:00:00 [migration/1]
root         7     2  0 08:09 ?        00:00:00 [ksoftirqd/1]
root         8     2  0 08:09 ?        00:00:00 [watchdog/1]
root         9     2  0 08:09 ?        00:00:00 [migration/2]
root        10     2  0 08:09 ?        00:00:00 [ksoftirqd/2]
root        11     2  0 08:09 ?        00:00:00 [watchdog/2]
root        12     2  0 08:09 ?        00:00:00 [migration/3]
root        13     2  0 08:09 ?        00:00:00 [ksoftirqd/3]
root        14     2  0 08:09 ?        00:00:00 [watchdog/3]
root        15     2  0 08:09 ?        00:00:00 [events/0]
[...]

• displaying of process status

 ps -x 

• reducing of list on running processes

 ps r 

Output of all running processes with extended information

 ps -ef

Output of memory occupancy per process

ps aux --sort -rss

Note: rss stands for resident set size - here is the excerpt of the ps manpage:

resident set size, the non-swapped physical memory that a task has used (inkiloBytes)

Graphical presentation of process hierarchy

• simple structure:

 ps axjf 

• better representation:

 pstree </pre







Translator: Alina Ranzinger

Alina has been working at Thomas-Krenn.AG since 2024. After her training as multilingual business assistant, she got her job as assistant of the Product Management and is responsible for the translation of texts and for the organisation of the department.