What is pkill in linux

pkill Linux Command | Explained

In Linux, the “pkill” command kills or terminates a running process based on its name. This command sends a specified signal, i.e., SIGTERM, to the utility to end the current process from the environment. The purpose of this guide is to explain the “pkill” command with practical implementations in Linux. The content that supports this article is enlisted below:

• How Does the pkill Command Work in Linux?
• How to Use the pkill Command in Linux?
  • Example 1: Kill a Specific Process Using Name
  • Example 2: Kill All Processes of Active User
  • Example 3: HangUp the Ping Process Using pkill
  • Example 4: Kill Process With Full Argument
  • Example 5: Kill Running Processes of Multiple Users
  • Example 6: Kill Gnome Process of Specific User
  • Example 7: Kill Most Recent Process

  How Does the pkill Command Work in Linux?

  The “pkill” command is quite useful for stopping a specified process in a hundred processes. The syntax of “pkill” commands with arguments is as follows:

  Syntax:

  In the above syntax, the “pkill” command acquires “options” that execute processes based on flags, and “pattern” specifies the regular expression. Different options and their descriptions are explained below:

  Options	Description
  -o	It means to kill the oldest processes.
  -n	The options kill the newest processes.
  -x	This option kills processes having the same pattern.
  -u	It refers to killing processes that are owned by other users.
  -signal	It sends a signal to the process.

  An alternative way is by sending a signal. Each signal has its functionalities, the three most common signals are enlisted below:

  Signal	Description
  1 (HUP)	This signal specifies reloading the process.
  9 (KILL)	It represents killing the process.
  15 (TERM)	The signal completely stops the process.

  To explore more options, you can utilize the “pkill –help” command in the terminal below:

  

  How to Use the pkill Command in Linux?

  This section enlists various examples to demonstrate the practical usage of skill Commands in Linux.

  Example 1: Kill a Specific Process Using Name

  An example is considered in which an existing process, “firefox”, is already running on our system. To stop this process, the “pkill” command is utilized in the below steps:

  Get the Process Name to be Killed:

  To display the list of all the active processes is possible through the “top” command as below:

  

  Terminate the Process:

  To terminate the existing process, specify the name of the process as “firefox” as below. Additionally, the value “-15” helps to stop the process without any environmental issues:

  

  Verify Terminated Process:

  Now, you can verify that the “firefox” process has been successfully terminated from the active processes:

  

  Let’s explore another aspect of the “pkill” command.

  Example 2: Kill All Processes of Active User

  Another example is carried out to remove all the current processes of active users by employing the “pkill” command. The steps are performed below:

  Currently, the active user “linux_user1” is initialized in our system. The “pkill” command can use the “-9” option to terminate all processes promptly. After that, specify the name of the active user with which you want to terminate all processes:

  

  After exiting the above command, all processes of “linux_user1” have been automatically terminated, and the window navigates to the login window as shown below:

  

  Example 3: HangUp the Ping Process Using pkill

  Each process, when invoked, is associated with a command which initiated it. Here, we will use the exact command to identify and kill a process using the “pkill” command:

  Initialize a Ping Process

  To initialize the process, the “ping” command is utilized with the “google.com” as seen in the below figure:

  

  It executes sequential processes with some millisecond time difference.

  HangUp the Ping Process

  The signal “-1” is utilized to reload/hang the ping process through the “pkill” command as below:

  

  You can verify that the ping process has been hanged after executing the above command on another terminal:

  

  The “Hangup” message at the output confirms that the pkill command has been successfully worked with the “-1” signal.

  Example 4: Kill Process With Full Argument

  To stop the execution, another terminal is opened and runs the below command specifying the initialized process name “ping google.com ”. The “-f” represents the full name of the process that you want to terminate:

  

  Example 5: Kill Running Processes of Multiple Users

  An example is considered to kill running processes of multiple users. For instance, we have two users in the current system, execute the below script to terminate their running processes:

  $ pkill -u root, itslinuxfoss

  

  Example 6: Kill Gnome Process of Specific User

  To kill the particular process of the specific user, specify the with “-u” utility and name of the process. In our case, terminate the Gnome that kills all processes of the “linux_user1” user:

  $ pkill -9 -u linux_user1 gnome

  

  Example 7: Kill Most Recent Process

  You can kill the most recent process by using the “– – oldest” utility with the name of the running process. For instance, the process of “firefox” will terminate after executing the below script:

  

  That’s all from this guide. We have covered Linux pkill command along with the seven efficient examples.

  Conclusion

  The “pkill” command stops the execution of currently active processes in the Linux operating system. It is quite useful to terminate the specified process that may be the cause of extra disk usage. The “pkill” command can be used with different options to kill processes such as “-f” (full process name), “-o” (oldest process), and “-n”(newest process). Additionally, users can utilize signals “1”, “9”, and “15” for “reloading”, “killing”, and “terminating” any process. This guide has explained “pkill” commands with their practical usage in the Linux system.

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  Pkill Command in Linux

  On Unix-like operating systems, the pgrep command searches for processes currently running on the system, based on a complete or partial process name, or other specified attributes. The pkill command sends a signal to one or more processes, using the same flexible selection methods as pgrep.

  What signal does Pkill?

  This command locates a specific process for a user. Terminate the process. When no signal is included in the pkill command-line syntax, the default signal that is used is –15 (SIGTERM). Using the –9 signal (SIGKILL) with the pkill command ensures that the process terminates promptly.

  How do I kill a process in Linux?

  1. What Processes Can You Kill in Linux?
  2. Step 1: View Running Linux Processes.
  3. Step 2: Locate the Process to Kill. Locate a Process with ps Command. Finding the PID with pgrep or pidof.
  4. Step 3: Use Kill Command Options to Terminate a Process. killall Command. pkill Command. .
  5. Key Takeaways on Terminating a Linux Process.

  How do I kill a Linux process by name?

  1. Kill Command – Kill the process by specifying its PID. .
  2. Killall Command – Kill processes by name. .
  3. Pkill Command – Send signal to the process based on its name. .
  4. Xkill Command – kill a client by X resource.

  How do I kill a process in Terminal?

  To kill a process use the kill command. Use the ps command if you need to find the PID of a process. Always try to kill a process with a simple kill command. This is the cleanest way to kill a process and has the same effect as cancelling a process.

  How do you kill a process in Terminal?

  How do you send a signal in Linux?

  1. SIGINT (Ctrl + C) – You know this already. Pressing Ctrl + C kills the running foreground process. This sends the SIGINT to the process to kill it.
  2. You can send SIGQUIT signal to a process by pressing Ctrl + \ or Ctrl + Y.

  What is the difference between kill and Pkill command?

  The main difference between these tools is that kill terminates processes based on Process ID number (PID), while the killall and pkill commands terminate running processes based on their names and other attributes.

  How do you send a signal?

  1. In Signal, tap compose. .
  2. Select a contact or enter a number to open that conversation.
  3. Tap the text input field.
  4. Type your message or attach a file.

  How do I start a process in Linux?

  The easiest way to start a process is to type its name at the command line and press Enter. If you want to start an Nginx web server, type nginx.

  What does kill in Linux?

  kill command in Linux (located in /bin/kill), is a built-in command which is used to terminate processes manually. kill command sends a signal to a process which terminates the process.

  How do you kill a process in Unix?

  1. Ctrl-C sends SIGINT (interrupt)
  2. Ctrl-Z sends TSTP (terminal stop)
  3. Ctrl-\ sends SIGQUIT (terminate and dump core)
  4. Ctrl-T sends SIGINFO (show information), but this sequence is not supported on all Unix systems.

  

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  What is the difference between kill , pkill and killall?

  I am familiar with kill command , and most of the time we just use kill -9 to kill a process forcefully, there are many other signals that can be used with kill . But I wonder what are the use cases of pkill and killall , if there is already a kill command. Do pkill and killall use the kill command in their implementation? I mean they are just wrappers over kill or they have their own implementation? I would also like to know how pgrep command gets the process id from the process name. Do all these commands use the same underlying system calls? Is there any difference from a performance point of view, which one is faster?

  Two things: Why use kill -9 by default? -15 (please stop) and -1 (modem has hung up, please CLEANLY closed yourself) are much more polite. Secondly. Beware of using killall on non-linux boxes. It might behave differently. (E.g. on solaris it kills all. NOT FILTERED on process names).

  3 Answers 3

  The kill command is a very simple wrapper to the kill system call, which knows only about process IDs (PIDs). pkill and killall are also wrappers to the kill system call, (actually, to the libc library which directly invokes the system call), but can determine the PIDs for you, based on things like, process name, owner of the process, session id, etc.

  How pkill and killall work can be seen using ltrace or strace on them. On Linux, they both read through the /proc filesystem, and for each pid (directory) found, traverses the path in a way to identify a process by its name or other attributes. How this is done is technically speaking, kernel and system specific. In general, they read from /proc//stat which contains the command name as the 2nd field. For pkill -f and pgrep examine the /cmdline entry for each PID’s proc entry.

  pkill and pgrep use the readproc system call, whereas killall does not. I couldn’t say if there’s a performance difference: you’ll have to benchmark that on your own.

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