How to Use ps Command on Linux

We’re here to help explain how to use ps command on Linux and garner information on the status of different processes run by the system. So read on to know more!

Processes are computer programs in execution. In a multitasking environment like Linux, the operating system runs several processes simultaneously. This is done by switching the execution of processes and assigning them to processors one by one. 

Also, there are several attributes maintained by the operating system for the owner’s processes and the associated security attributes. 

How to Use ps Command on Linux

In Linux, you can use the ps command to see the details of all the processes running in the system. Information like process name, owner, session, etc. can be obtained about each process. In this guide, we discuss the ps command in detail along with its various options.

ps command

The ps command stands for process status. It displays the list of all the processes running in the system with their attributes. The information about these processes is read from the /proc file system. This is a virtual file system containing virtual files. Among the information displayed by the ps command includes:

• PID – The unique process Id associated with every process
• TTY – The terminal user is logged into
• TIME – The amount of time the process has been running in minutes
• CMD – The command that has launched the process

Hint: Sometimes, when we run the ps command, it displays the TIME as 00:00:00. This means the central processing unit (CPU) has not been allocated by the operating system to this process so far. 

For instance, the bash command is generally associated with 0 CPU time because it is a parent process for executing other processes and doesn’t utilize CPU time.

ps command usage with no arguments

When the ps command is run without any arguments, it shows the list of interactive processes in the system. This is the list of processes associated with the shell. The following command illustrates how we can find the list of interactive methods. On your system, open the terminal and type the following command:

$ps

Listing all the processes

Irrespective of the process types, all the processes running in the system can be seen using the –A option. The following command illustrates this:

$ps -A

Also, you can use the –e option to view all the processes as follows:

$ps -e

Showing all processes not associated with the terminal

The following command can be used to list down all the processes that are not associated with any terminal:

$ps -a

Showing all the running/active processes

Every processes that are running or active in the background can be shown by typing the following command:

$ps -r

Processes of the current user

All the processes of the current user can be listed down with the help of the –x option. The following command illustrates it:

$ps -x

Listing down a specific process attribute

The –C option can be used to list down a specific process by name. We can specify the process name. For instance, the following command list down the details of the gedit process:

$ps -C gedit

Listing down a specific group of process

We can specify a specific group for the process. The –G option is used for this purpose, and the group ID is the user group that created the process. The following command shows how we can list the process for the group faculty:

$ps -G faculty

Listing down a process based on their process Id

We can also use the process ID to search for the process and list its attributes. The following command searches for the process with ID 4792 and shows its attributes:

$ps -p 4792

Viewing all the processes belonging to a specific session Id

To view the processes belonging to a specific session ID, -s or –sId options can be used with the ps command as shown below:

$ps -s 1391

or

$ps -sId 1391

Select the process based on tty

Based on the terminal (tty), the processes can be filtered using the –t or –tty option. The following command shows that:

$ps -t pts/0

List the processes for a specific user

The –U command can list the process by name or ID for a specific user. The following command selects the processes for user khan as follows:

$ps -U khan

Listing process as a tree

We can also use the --forest command to list down the process as a tree. It will display the processes along with their parent-child relationship. The following command illustrates this:

$ps --forest -x

Other options

There are many other options available with the ps command. For instance, we can list down the process with a complete format listing by using the –f option. You can also use -F to view the full extra format, --format to view the process details with the user-defined format. 

And the -j option will  be used for BSD format, l for long BSD format, -v for virtual memory format. For instance, to list down the process with their id, name, CPU, memory usage, and command, the following can be used:

$ps -e -o pid,uname,pcpu,pmem,comm

You can even rename the labels for each column as follows:

$ps -e -o pid=PID,uname=USERNAME,pcpu=CPU_USAGE,pmem=%MEM,comm=COMMAND

You can list down the threads of a process using –T or –L options. Moreover, you can also sort the processes while listing them down. For instance, the following process lists down the processes based on their memory:

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

Tip: You can pip the ps command with grep to custom search for a specific process

We have discussed the ps command that can be used to find out the information about processes running in the system. Moreover, we can filter these processes based on the current user, group, session, terminal, etc. We can also specify the custom format to list the processes. We have discussed a range of options for the ps command. 

More information can be obtained about the ps command from the Linux manual.

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