pkill is a command-line utility, used to send signals to the processes of a running program. The processes can be specified by their names, by a user name, or other attributes. In this article we will discuss about pkill command in Linux.
By default the
pkill command comes pre-installed as a part of the
procps package on most of Linux distributions.
Use of pkill Command
The basic syntax for the
pkill command is as follows:
pkill [OPTIONS] [PATTERN]
[PATTERN] is specified using extended regular expressions.
If you run the
pkill command without any option, it sends the
TERM) signal to the PIDs of all running programs that match with the given name. For example, to stop the all processes of the Google Chrome, you would run:
pkill -9 google-chrome
It will returns
0 as exit code if any one running process match otherwise it will returns
1. Exit codes are useful while you are writing shell scripts.
To send the different signals to the matched process use the
--signal option followed by the signal number or name.
To get the list of all available signals use kill
Following are the most common signals:
HUP): to reload a process.
KILL): to kill a process.
TERM): to gracefully stop a process.
Signals can be specified in three different ways:
- using a number (e.g., -1)
- with the “SIG” prefix (e.g., -SIGHUP)
- without the “SIG” prefix (e.g., -HUP).
For example, to reload the Nginx processes you would run:
pkill -HUP nginx
pkill uses regular expressions to match the processes names. It is always a good idea to use the pgrep command to print the matched processes before sending signals to them.
For example, to list all processes that contain “ssh” in their names:
2045 sshd 2154 ssh-agent 8506 ssh 1259 ssh-agent
If you want to send a signal only to the processes which names are exactly as the search pattern, you would use:
pkill command matches the process name by default. You would use
-f option to match against full argument lists.
pkill -9 -f "ping 188.8.131.52"
-u option with
pkill to match processes being run by a specified user:
pkill -u kunj
Specify the multiple users by separating their names with commas:
pkill -u kunj,tecnstuff
You can combine options and search patterns. For example to send KILL signal all processes that run under user “kunj” and contains “gnome” in their names you would type:
pkill -9 -u kunj gnome
-n option to get most recent and
-o for oldest started process.
For example, to kill the most recently created screen:
pkill -9 -n screen
This article shows you how to use the
pkill command to send signals to running programs based on different criteria. To learn more about the
pkill command, take a look at pkill man page.
Feel free to leave a comment if you have any question or feedback.