pkill

What it does

pgrep PATTERN prints the PIDs of processes whose name matches the pattern (a regular expression). pkill PATTERN sends them a signal (TERM by default). Both select with the same options: by user (-u), terminal (-t), parent (-P), full command line (-f) and more.

Run pgrep first with the same options to see what pkill would hit.

How to write it

pgrep [OPTION]... PATTERN
pkill [OPTION]... [-SIGNAL] PATTERN
pidwait [OPTION]... PATTERN

Options 32

Most used

Signal (pkill)

-SIGNAL, --signal SIGNAL: The signal to send (default TERM).
-e, --echo: Show what was killed.
-q, --queue VALUE: Send a value with the signal.
-H, --require-handler: Only processes that handle the signal.

Output (pgrep)

-l, --list-name: Show the name with the PID.
-a, --list-full: Show the full command line.
-c, --count: Only the number of matches.
-d, --delimiter TEXT: Separator between PIDs.
-w, --lightweight: Show thread IDs.

Select

-f, --full: Match the whole command line, not only the name.
-u, --euid USERS: Effective user.
-U, --uid USERS: Real user.
-G, --group GIDS: Real group.
-g, --pgroup PGRPS: Process group.
-s, --session SIDS: Session.
-t, --terminal TERMS: Terminal, like pts/1.
-P, --parent PPIDS: Children of these parents.
-n, --newest: Only the newest match.
-o, --oldest: Only the oldest match.
-O, --older SECONDS: Only processes older than this.
-x, --exact: The name must match exactly.
-i, --ignore-case: Ignore case.
-v, --inverse: Everything that does not match.
-r, --runstates STATES: Only these states (D, R, S, Z …).
-A, --ignore-ancestors: Leave out the own parents.
-F, --pidfile FILE: Read PIDs from a file.
-L, --logpidfile: Fail if the PID file is not locked.
--cgroup NAMES: Only these cgroups.
--ns PID: Same namespaces as PID.
--nslist NAMES: Which namespaces to compare.
-h, --help: Show help.
-V, --version: Show the version.

Examples 11

$ run as a normal user# run as root (or with sudo)

1Find PIDs by name
```
$pgrep -l sshd
1010 sshd
2210 sshd
```
-l adds the name.
2See full command lines
```
$pgrep -a python3
```
Find which script is running.
3Stop all processes of a user
```
#pkill -u olduser
```
Before you delete the account.
4Log out a session
```
#pkill -KILL -t pts/3
```
Ends everything on that terminal.
5Match the full command line
```
$pgrep -af 'backup.sh'
$pkill -f 'backup.sh'
```
The process name is bash; -f finds the script.
6Count processes
```
$pgrep -c httpd
6
```
Quick health check.
7Wait until a process is gone
```
$pidwait -f backup.sh; echo "backup finished"
```
Then start the next step.
8Reload a daemon by name
```
#pkill -HUP rsyslogd
```
Re-reads the config.
9The newest or oldest match
```
$pgrep -n firefox; pgrep -o httpd
```
-o httpd = the parent of all httpd children.
10Hunt processes that run from /tmp (security)
```
#pgrep -af '/tmp/|/dev/shm/'
```
Suspicious locations for running programs.
11Show what pkill did
```
#pkill -e dd
dd killed (pid 4123)
```
Proof of the action.

Watch out

The pattern is a regular expression and matches part of the name: pkill ssh also hits ssh-agent and sshd. Use -x for an exact name.
Test with pgrep (same options) before pkill.

Exit codes

`0`	At least one process matched.
`1`	No process matched.
`2`	Syntax error.
`3`	Fatal error.

`pkill`

What it does

How to write it

Options 32

Signal (pkill)

Output (pgrep)

Select

Examples 11

1Find PIDs by name

2See full command lines

3Stop all processes of a user

4Log out a session

5Match the full command line

6Count processes

7Wait until a process is gone

8Reload a daemon by name

9The newest or oldest match

10Hunt processes that run from /tmp (security)

11Show what pkill did

Watch out

Exit codes

Full manual

What it does

How to write it

Options 32

Signal (pkill)

Output (pgrep)

Select

Examples 11

1Find PIDs by name

2See full command lines

3Stop all processes of a user

4Log out a session

5Match the full command line

6Count processes

7Wait until a process is gone

8Reload a daemon by name

9The newest or oldest match

10Hunt processes that run from /tmp (security)

11Show what pkill did

Watch out

Exit codes

Related commands

Used in these lessons

Used in these labs

Full manual

`pkill`