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The pkill command allows you to kill a program simply by specifying the name. For instance if you want to kill all open terminals with the same process ID you can type the following:

pkill term

You can return a count of the number of processes killed by supplying the -c switch as follows:

pkill -c <programname>

The output will simply be the number of processes killed.

To kill all the processes for a particular user run the following command:

pkill -u <userid>

To find the effective user id for a user use the ID command as follows:

id -u <username>

For example:

id -u gary

You can also kill all the processes for a particular user using the real user ID as follows:

pkill -U <userid>

The real user ID is the ID of the user running the process. In most cases it will be the same as the effective user but if the process was run using elevated privileges then the real user ID of the person running the command and the effective user will be different.

To find the real user ID use the following command.

id -ru <userid>

You can also kill all the programs in a particular group by using the following commands

pkill -g <processgroupid>
pkill -G <realgroupid>

The process group id is the group id running the process whereas the real group id is the process group of the user who physically ran the command.

These may be different if the command was ran using elevated privileges.

To find the group id for a user run the following ID command:

id -g

To find the real group id using the following ID command:

id -rg

You can limit the amount of processes pkill actually kills. For instance killing all of a users processes is probably not what you want to do. But you can kill their latest process by running the following command.

pkill -n <programname>

Alternatively to kill the oldest program run the following command:

pkill -o <programname>

Imagine two users are running Firefox and you just want to kill the version of Firefox for a particular user you can run the following command:

pkill -u <uid> firefox

You can kill all processes which have a specific parent ID. To do so run the following command:

pkill -P <parentprocessID>

You can also kill all processes with a specific session ID by running the following command:

pkill -s <sessionID>

Finally you can also kill all processes running on a particular terminal type by running the following command:

pkill -t <terminal>

If you want to kill a lot of processes you can open a file using an editor such as nano and enter each process on a separate line. After saving the file you can run the following command to read the file and kill each process listed within it.

pkill -F /path/to/file

The Pgrep Command

Before running the pkill command it is worth seeing what the effect of the pkill command will be by running the pgrep command

The pgrep command uses the same switches as the pkill command and a few extra ones.


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Old News ;-)

[Oct 27, 2017] Neat trick of using su command for killing all processes for a particular user

Oct 27, 2017 | unix.stackexchange.com

If you pass -1 as the process ID argument to either the kill shell command or the kill C function , then the signal is sent to all the processes it can reach, which in practice means all the processes of the user running the kill command or syscall.

su -c 'kill -TERM -1' bob

In C (error checking omitted):

if (fork() == 0) {
    setuid(uid);
    signal(SIGTERM, SIG_DFL);
    kill(-1, SIGTERM);
}

[Oct 27, 2017] c - How do I kill all a user's processes using their UID - Unix Linux Stack Exchange

Oct 27, 2017 | unix.stackexchange.com

osgx ,Aug 4, 2011 at 10:07

Use pkill -U UID or pkill -u UID or username instead of UID. Sometimes skill -u USERNAME may work, another tool is killall -u USERNAME .

Skill was a linux-specific and is now outdated, and pkill is more portable (Linux, Solaris, BSD).

pkill allow both numberic and symbolic UIDs, effective and real http://man7.org/linux/man-pages/man1/pkill.1.html

pkill - ... signal processes based on name and other attributes

    -u, --euid euid,...
         Only match processes whose effective user ID is listed.
         Either the numerical or symbolical value may be used.
    -U, --uid uid,...
         Only match processes whose real user ID is listed.  Either the
         numerical or symbolical value may be used.

Man page of skill says is it allowed only to use username, not user id: http://man7.org/linux/man-pages/man1/skill.1.html

skill, snice ... These tools are obsolete and unportable. The command syntax is poorly defined. Consider using the killall, pkill

  -u, --user user
         The next expression is a username.

killall is not marked as outdated in Linux, but it also will not work with numberic UID; only username: http://man7.org/linux/man-pages/man1/killall.1.html

killall - kill processes by name

   -u, --user
         Kill only processes the specified user owns.  Command names
         are optional.

I think, any utility used to find process in Linux/Solaris style /proc (procfs) will use full list of processes (doing some readdir of /proc ). I think, they will iterate over /proc digital subfolders and check every found process for match.

To get list of users, use getpwent (it will get one user per call).

skill (procps & procps-ng) and killall (psmisc) tools both uses getpwnam library call to parse argument of -u option, and only username will be parsed. pkill (procps & procps-ng) uses both atol and getpwnam to parse -u / -U argument and allow both numeric and textual user specifier.

; ,Aug 4, 2011 at 10:11

pkill is not obsolete. It may be unportable outside Linux, but the question was about Linux specifically. – Lars Wirzenius Aug 4 '11 at 10:11

Petesh ,Aug 4, 2011 at 10:58

to get the list of users use the one liner: getent passwd | awk -F: '{print $1}' – Petesh Aug 4 '11 at 10:58

; ,Aug 4, 2011 at 12:07

what about I give a command like: "kill -ju UID" from C system() call? – user489152 Aug 4 '11 at 12:07

osgx ,Aug 4, 2011 at 15:01

is it an embedded linux? you have no skill, pkill and killall? Even busybox embedded shell has pkill and killall. – osgx Aug 4 '11 at 15:01

michalzuber ,Apr 23, 2015 at 7:47

killall -u USERNAME worked like charm – michalzuber Apr 23 '15 at 7:47

How To List And Kill Processes Using The PGrep And PKill Commands

The PKill command allows you to kill a program simply by specifying the name. For instance if you want to kill all open terminals with the same process ID you can type the following:

pkill term

You can return a count of the number of processes killed by supplying the -c switch as follows:

pkill -c <programname>

The output will simply be the number of processes killed.

To kill all the processes for a particular user run the following command:

pkill -u <userid>

To find the effective user id for a user use the ID command as follows:

id -u <username>

For example:

id -u gary

You can also kill all the processes for a particular user using the real user ID as follows:

pkill -U <userid>

The real user ID is the ID of the user running the process. In most cases it will be the same as the effective user but if the process was run using elevated privileges then the real user ID of the person running the command and the effective user will be different.

To find the real user ID use the following command.

id -ru <userid>

You can also kill all the programs in a particular group by using the following commands

pkill -g <processgroupid>
pkill -G <realgroupid>

The process group id is the group id running the process whereas the real group id is the process group of the user who physically ran the command.

These may be different if the command was ran using elevated privileges.

To find the group id for a user run the following ID command:

id -g

To find the real group id using the following ID command:

id -rg

You can limit the amount of processes pkill actually kills. For instance killing all of a users processes is probably not what you want to do. But you can kill their latest process by running the following command.

pkill -n <programname>

Alternatively to kill the oldest program run the following command:

pkill -o <programname>

Imagine two users are running Firefox and you just want to kill the version of Firefox for a particular user you can run the following command:

pkill -u <uid> firefox

You can kill all processes which have a specific parent ID. To do so run the following command:

pkill -P <parentprocessID>

You can also kill all processes with a specific session ID by running the following command:

pkill -s <sessionID>

Finally you can also kill all processes running on a particular terminal type by running the following command:

pkill -t <terminal>

If you want to kill a lot of processes you can open a file using an editor such as nano and enter each process on a separate line. After saving the file you can run the following command to read the file and kill each process listed within it.

pkill -F /path/to/file