The PS, a.k.a. “process status”, is a native command-line utility for UNIX-based systems to monitor the currently running processes in your system.
It reads the information from the virtual files in the /proc filesystem and gives the running processes information like memory consumption, CPU usage, PID, command name, etc.
The output of this command varies depending on the running processes and the parameter used to view the list of processes.
Tutorial Details
| Description | PS (Process Status) |
| Difficulty Level | Moderate |
| Root or Sudo Privileges | No |
| Host System and Architecture | Ubuntu 22.10 (x64) |
| OS Compatibility | Ubuntu, Manjaro, Fedora, etc. |
| Prerequisites | ps |
| Internet Required | No |
| Discussed Tools in this Article |
Syntax of the PS Command
The ps command takes only one argument as an option.
$ ps [OPTION]It will list the running processes in your current shell without any arguments.
$ ps
PID TTY TIME CMD
6846 pts/0 00:00:00 bash
9583 pts/0 00:00:00 psNote that you always see the ps process in the output when you execute this command, as ps is also a process.
The PS command output column breakdown is as follows:
| Columns | Description |
|---|---|
| PID | It will display the unique process ID of the running command |
| TTY | Terminal type that the user is logged into |
| TIME | The amount of CPU utilization time used to run the process |
| CMD | Command name |
The PS command supports three types of syntax styles:
| Syntax | Description |
|---|---|
| UNIX | Might be grouped and preceded by a hyphen. |
| BSD | Might be grouped but not preceded by a hyphen. |
| GNU | Long options and preceded by double hyphens. |
In Linux, every process has several IDs associated with it that you must know before understanding the PS command.
| IDs | Description |
|---|---|
| Process ID (PID) | It is a temporary ID associated with the process when it is initialized, and once the process exits and the parent process retrieves the exit status, the PID is free to be reused by a new process. |
| Parent Process ID (PPID) | At every execution of a program, the kernel creates a process that uses the fork() system call to load execution details in memory; this process is known as the “parent process,” which is responsible for creating the “child process.” If the parent process exits before the child, then the child’s PPID is changed to another process (usually PID 1). |
| Process Group ID (PGID) | The process group is used to manage processes in Linux that share PGIDs. If the PID is equal to the PGID, then this process is a process group leader. |
| Session ID (SID) | If the PID is equal to the SID, then this process is the session leader. |
The PGID (Process Group) and SID (Session ID) are ways to manage multiple related processes as a unit.
A group of multiple process groups might belong to the same session, and the same session might hold multiple process groups.
Listing All Running Processes in Your System
The “-A” or “-e” flag will list all the running processes in your Linux system in generic (Unix/Linux) format.
$ ps -A
PID TTY TIME CMD
1 ? 00:00:09 systemd
2 ? 00:00:00 kthreadd
3 ? 00:00:00 rcu_gp
4 ? 00:00:00 rcu_par_gp
5 ? 00:00:00 netnsExecute the following command to list all the active processes in BSD format:
$ ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.1 0.1 166772 12020 ? Ss 12:45 0:10 /sbin/init au
root 2 0.0 0.0 0 0 ? S 12:45 0:00 [kthreadd]
root 3 0.0 0.0 0 0 ? I< 12:45 0:00 [rcu_gp]
root 4 0.0 0.0 0 0 ? I< 12:45 0:00 [rcu_par_gp]
root 5 0.0 0.0 0 0 ? I< 12:45 0:00 [netns]List only the specific process that matches a string used as an argument to the grep command.
$ ps aux | grep nginx
root 2540 0.0 0.0 6268 4920 ? S 12:45 0:00 nginx: master process nginx -g daemon off;
systemd+ 2556 0.0 0.0 6916 4268 ? S 12:45 0:01 nginx: worker process
systemd+ 2557 0.0 0.0 6772 4212 ? S 12:45 0:00 nginx: worker process
systemd+ 2558 0.0 0.0 6756 1984 ? S 12:45 0:00 nginx: worker process
systemd+ 2559 0.0 0.0 6756 1984 ? S 12:45 0:00 nginx: worker processUse the “--no-header” flag to list the running process without a header.
$ ps --no-header
6846 pts/0 00:00:00 bash
34851 pts/0 00:00:00 psListing the Processes Not Associated with the Terminal
The “-a” flag will display all the running processes except for the session leaders and processes that are not associated with a terminal.
$ ps -a
PID TTY TIME CMD
5912 tty2 00:00:00 gnome-session-b
6887 pts/1 00:00:00 man
6908 pts/1 00:00:00 pager
14628 pts/0 00:00:00 psListing All Processes Except Session Leaders
The “-d” flag will list all the running processes except for the session leader processes.
$ ps -d
PID TTY TIME CMD
2 ? 00:00:00 kthreadd
3 ? 00:00:00 rcu_gp
4 ? 00:00:00 rcu_par_gp
5 ? 00:00:00 netnsListing All Processes with Full-Format Listings
The “-f” or “-F” flag can be combined with other options to add additional columns like “UID” or “PPID“.
$ ps -af
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 5912 5909 0 12:49 tty2 00:00:00 /usr/libexec/gnome-session-b
linuxtl+ 18045 6866 0 14:21 pts/1 00:00:00 man ps
linuxtl+ 18053 18045 0 14:21 pts/1 00:00:00 pager
linuxtl+ 19386 6846 0 14:32 pts/0 00:00:00 ps -afListing All Processes Except Those That Fulfill the Specified Conditions (Negates the Selection)
Using the “-N” or “--deselect” flag will list all the processes except those that are fulfilled by the specified conditions (the opposite of selection).
For example, if you specify “-a” with “-N“, it will show you the opposite result that only includes the processes with both session leaders and processes not associated with a terminal.
$ ps -a -N
PID TTY TIME CMD
1 ? 00:00:10 systemd
2 ? 00:00:00 kthreadd
3 ? 00:00:00 rcu_gp
4 ? 00:00:00 rcu_par_gp
5 ? 00:00:00 netnsListing All Processes Associated With the Current Terminal
The “t” or “T” flag will list all the processes associated with your current terminal.
$ ps t
PID TTY STAT TIME COMMAND
6846 pts/0 Ss 0:00 bash
17328 pts/0 R+ 0:00 ps tListing Only the Running Processes Associated With the Current Terminal
The “r” or “-r” flag will only list the running processes associated with your current terminal.
$ ps r
PID TTY STAT TIME COMMAND
17428 pts/0 R+ 0:00 ps rListing Only the Processes Owned by You
The “x” or “-x” flag will only list the processes owned by the current logged-in user.
$ ps x
PID TTY STAT TIME COMMAND
5811 ? Ss 0:06 /lib/systemd/systemd --user
5812 ? S 0:00 (sd-pam)
5819 ? S<sl 0:00 /usr/bin/pipewire
5820 ? Ssl 0:00 /usr/bin/pipewire-media-sessionListing Processes by Real or Effective User ID
Use the “-U” flag to list the processes based on real user ID (RUID) or name, or use the “-u” flag to list the processes based on effective user ID (EUID) or name, along with the “-f” flag to print the additional columns.
$ ps -fU linuxtldr
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 5811 1 0 12:49 ? 00:00:07 /lib/systemd/systemd --user
linuxtl+ 5812 5811 0 12:49 ? 00:00:00 (sd-pam)
linuxtl+ 5819 5811 0 12:49 ? 00:00:00 /usr/bin/pipewireOr
$ ps -fu 1003
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 5811 1 0 12:49 ? 00:00:07 /lib/systemd/systemd --user
linuxtl+ 5812 5811 0 12:49 ? 00:00:00 (sd-pam)
linuxtl+ 5819 5811 0 12:49 ? 00:00:00 /usr/bin/pipewireListing All Processes Running as Root
The following command will list all the processes running as root in real or effective user format.
$ ps -U root -u root
PID TTY TIME CMD
1 ? 00:00:12 systemd
2 ? 00:00:00 kthreadd
3 ? 00:00:00 rcu_gp
4 ? 00:00:00 rcu_par_gp
5 ? 00:00:00 netnsListing the Group of Processes (Real or Effective Group ID)
Execute the following command to get the list of processes owned by a specific group (real group ID or name).
$ ps -fG root
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 12:45 ? 00:00:12 /sbin/init auto noprompt spl
root 2 0 0 12:45 ? 00:00:00 [kthreadd]
root 3 2 0 12:45 ? 00:00:00 [rcu_gp]
root 4 2 0 12:45 ? 00:00:00 [rcu_par_gp]
root 5 2 0 12:45 ? 00:00:00 [netns]
root 7 2 0 12:45 ? 00:00:00 [kworker/0:0H-events_highpri
root 9 2 0 12:45 ? 00:00:01 [kworker/0:1H-events_highpri
root 10 2 0 12:45 ? 00:00:00 [mm_percpu_wq]Execute the following command to list the processes owned by the effective group name (or session).
$ ps -fg root
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 12:45 ? 00:00:12 /sbin/init auto noprompt spl
root 2 0 0 12:45 ? 00:00:00 [kthreadd]
root 3 2 0 12:45 ? 00:00:00 [rcu_gp]
root 4 2 0 12:45 ? 00:00:00 [rcu_par_gp]
root 5 2 0 12:45 ? 00:00:00 [netns]
root 7 2 0 12:45 ? 00:00:00 [kworker/0:0H-events_highpri
root 9 2 0 12:45 ? 00:00:01 [kworker/0:1H-kblockd]
root 10 2 0 12:45 ? 00:00:00 [mm_percpu_wq]Displaying Specific Process Information with PID or PPID
The following command will list the information for the specified process PID.
$ ps -fp 6846
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 6846 6820 0 12:50 pts/0 00:00:00 bashUse the following command to specify PPID.
$ ps -f --ppid 6820
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 6846 6820 0 12:50 pts/0 00:00:00 bashTo list the group of processes with multiple PIDs.
$ ps -fp 6820,154,5
UID PID PPID C STIME TTY TIME CMD
root 5 2 0 12:45 ? 00:00:00 [netns]
root 154 2 0 12:45 ? 00:00:00 [ipv6_addrconf]
linuxtl+ 6820 5811 0 12:50 ? 00:00:41 /usr/libexec/gnome-terminal-Listing the Processes Based on TTY
Use the “-t” flag to list the processes based on tty.
$ ps -f -t pts/0
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 6846 6820 0 12:50 pts/0 00:00:00 bash
linuxtl+ 22959 6846 0 15:02 pts/0 00:00:00 ps -f -t pts/0Or
$ ps -f -t pts/1
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 6866 6820 0 12:50 pts/1 00:00:00 bash
linuxtl+ 18045 6866 0 14:21 pts/1 00:00:00 man ps
linuxtl+ 18053 18045 0 14:21 pts/1 00:00:00 pagerOr
$ ps -f -t tty2
UID PID PPID C STIME TTY TIME CMD
linuxtl+ 5909 5743 0 12:49 tty2 00:00:00 /usr/libexec/gdm-wayland-ses
linuxtl+ 5912 5909 0 12:49 tty2 00:00:00 /usr/libexec/gnome-session-bASCII Art Process Tree
Use the “--forest” flag to display the list of processes linked to each other in ASCII art.
$ ps -e --forest
PID TTY TIME CMD
2 ? 00:00:00 kthreadd
3 ? 00:00:00 \_ rcu_gp
6812 ? 00:00:00 \_ gnome-terminal
6815 ? 00:00:00 | \_ gnome-terminal.
6820 ? 00:00:43 \_ gnome-terminal-
6846 pts/0 00:00:00 | \_ bash
23312 pts/0 00:00:00 | | \_ ps
6866 pts/1 00:00:00 | \_ bash
23147 pts/1 00:00:00 | \_ man
23155 pts/1 00:00:00 | \_ pager
6859 ? 00:00:00 \_ gnome-terminal
6861 ? 00:00:00 \_ gnome-terminal.Grep the name of the process to print the specific process tree.
$ ps -e --forest | grep gnome-terminal
6812 ? 00:00:00 \_ gnome-terminal
6815 ? 00:00:00 | \_ gnome-terminal.
6820 ? 00:00:44 \_ gnome-terminal-
6859 ? 00:00:00 \_ gnome-terminal
6861 ? 00:00:00 \_ gnome-terminal.Listing the Processes with Custom Output Format
Execute the following command with “L” to get the list of valid format specifiers.
$ ps L
cp CP
cpuid CPUID
cputime TIME
cputimes TIME Use the “-o” or “--format” flag to list the running process in the above format.
The following command will list the running processes with their PID, PPID, username, group, and command.
$ ps -eo pid,ppid,user,group,cmd
PID PPID USER GROUP CMD
1 0 root root /sbin/init auto noprompt splash
2 0 root root [kthreadd]
3 2 root root [rcu_gp]
4 2 root root [rcu_par_gp]
5 2 root root [netns]Listing Parent and Child Processes
Use the “-C” flag to list all the processes with the specified command name, including its child processes.
$ ps -C nginx
PID TTY TIME CMD
2540 ? 00:00:00 nginx
2556 ? 00:00:01 nginx
2557 ? 00:00:00 nginx
2558 ? 00:00:00 nginx
2559 ? 00:00:00 nginx
21648 ? 00:00:00 nginx
21649 ? 00:00:00 nginx
21650 ? 00:00:00 nginx
21651 ? 00:00:00 nginx
21652 ? 00:00:00 nginxThat was the end of the PS command examples.
This command is very useful.
If any examples are missed that must be included in this article, let us know in the comment section.
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