--- name: "pkill" section: "1" platform: "linux" package: "procps-ng" version: "4.0.7-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd", "openbsd", "macos"] url: "https://new.carta.tech/pgrep" --- # pkill(1) look up, signal, or wait for processes based on name and other attributes Part of [pgrep(1)](/pgrep/1.md). ## NAME pgrep, pkill, pidwait - look up, signal, or wait for processes based on name and other attributes ## SYNOPSIS **pgrep** \[*option* ...\] *pattern* **pkill** \[*option* ...\] *pattern* **pidwait** \[*option* ...\] *pattern* ## DESCRIPTION **pgrep** looks through the currently running processes and lists the process IDs which match the selection criteria to stdout. All the criteria have to match. For example, - $ pgrep -u root sshd will only list the processes whose name include **sshd** AND owned by **root**. On the other hand, - $ pgrep -u root,daemon will list the processes owned by **root** OR **daemon**. **pkill** will send the specified signal (by default **SIGTERM**) to each process instead of listing them on stdout. **pidwait** will wait for each process instead of listing them on stdout. ## OPTIONS - **-***signal* **--signal** *signal* Defines the signal to send to each matched process. Either the numeric or the symbolic signal name can be used. In **pgrep** or **pidwait** mode only the long option can be used and has no effect unless used in conjunction with **--require-handler** to filter to processes with a userspace signal handler present for a particular signal. - **-a**, **--list-full** List the full command line as well as the process ID. (**pgrep** only.) - **-A**, **--ignore-ancestors** Ignore all ancestors of **pgrep**, **pkill**, or **pidwait**. For example, this can be useful when elevating with **sudo** or similar tools. - **-c**, **--count** Suppress normal output; instead print a count of matching processes. When count does not match anything, e.g. returns zero, the command will return non-zero value. Note that for pkill and pidwait, the count is the number of matching processes, not the processes that were successfully signaled or waited for. - **-d**, **--delimiter** *delimiter* Sets the string used to delimit each process ID in the output (by default a newline). (**pgrep** only.) - **-e**, **--echo** Display name and PID of the process being killed. (**pkill** only.) - **-f**, **--full** The *pattern* is normally only matched against the process name. When **-f** is set, the full command line is used. - **-F**, **--pidfile** *file* Read *PID*s from *file*. This option is more useful for **pkill** or **pidwait** than **pgrep**. The filename "-" can be used to read from *STDIN*. Conflicts with the **--pid** option. - **-g**, **--pgroup** *pgrp*,... Only match processes in the process group IDs listed. Process group 0 is translated into **pgrep**'s, **pkill**'s, or **pidwait**'s own process group. - **-G**, **--group** *gid*,... Only match processes whose real group ID is listed. Either the numerical or symbolical value may be used. - **-H**, **--require-handler** Only match processes with a userspace signal handler present for the signal to be sent. - **-i**, **--ignore-case** Match processes case-insensitively. - **-l**, **--list-name** List the process name as well as the process ID. (**pgrep** only.) - **-L**, **--logpidfile** Fail if pidfile (see **-F**) not locked. - **-m**, **--mrelease** After sending the signal, invoke the **process\_mrelease**() system call to immediately free the target process's memory. - **-n**, **--newest** Select only the newest (most recently started) of the matching processes. - **-o**, **--oldest** Select only the oldest (least recently started) of the matching processes. - **-O**, **--older** *secs* Select processes older than secs. - **-p**, **--pid** *pid*,... Only match processes whose process ID is listed. Conflicts with the **--pidfile** option. - **-P**, **--parent** *ppid*,... Only match processes whose parent process ID is listed. - **-q**, **--queue** *value* **Send the integer** *value* along with the signal. This option will either use [**pidfd\_send\_signal**(2)](/pidfd_send_signal/2.md) with a value applied or [**sigqueue**(3)](/sigqueue/3.md) rather than [**kill**(2)](/kill/2.md). If the receiving process has installed a handler for this signal using the SA\_SIGINFO flag to [**sigaction**(2)](/sigaction/2.md), then it can obtain this data via the si\_value field of the siginfo\_t structure. - **-Q**, **--shell-quote** Output the command line in shell-quoted form. (**pgrep** only.) - **-r**, **--runstates** *D,R,S,Z,*... Match only processes which match the process state. - **-s**, **--session** *sid*,... Only match processes whose process session ID is listed. Session ID 0 is translated into **pgrep**'s, **pkill**'s, or **pidwait**'s own session ID. - **-t**, **--terminal** *term*,... Only match processes whose controlling terminal is listed. The terminal name should be specified without the "/dev/" prefix. - **-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. - **-v**, **--inverse** Negates the matching. This option is usually used in **pgrep**'s or **pidwait**'s context. In **pkill**'s context the short option is disabled to avoid accidental usage of the option. - **-w**, **--lightweight** Shows all thread ids instead of pids in **pgrep**'s or **pidwait**'s context. In **pkill**'s context this option is disabled. - **-x**, **--exact** Only match processes whose names (or command lines if **-f** is specified) **exactly** match the *pattern*. - **--cgroup** *name***,...** **Match on provided control group (cgroup) v2 name. See** [**cgroups**(7)](/cgroups/7.md) - **--env** *name*\[*=value*\],... Match on process that have these environment variables. If the *=value* parameter is not defined then only the variable name is matched. - **--ns** *pid* **Match processes that belong to the same namespaces. Required to run as** **root to match processes from other users. See --nslist** for how to limit which namespaces to match. - **--nslist** *name***,...** **Match only the provided namespaces. Available namespaces:** **ipc, mnt, net, pid, user, uts.** - **--quiet** Do not write anything to standard output (**pgrep** only). - **-V**, **--version** Display version information and exit. - **-h**, **--help** Display help and exit. ## OPERANDS - *pattern* Specifies an Extended Regular Expression for matching against the process names or command lines. ## EXAMPLES Example 1: Find the process ID of the **named** daemon: - $ pgrep -u root named Example 2: Make **syslog** reread its configuration file: - $ pkill -HUP syslogd Example 3: Give detailed information on all **bash** processes: - $ ps -fp $(pgrep -d, -x bash) Example 4: Make all **chrome** processes run nicer: - $ renice +4 $(pgrep chrome) Example 5: Wait for a process with a known PID to finish: - $ echo ${PID} \| pidwait -F - ## EXIT STATUS - **0** One or more processes matched the criteria. For **pkill** and **pidwait**, one or more processes must also have been successfully signalled or waited for. - **1** No processes matched or none of them could be signalled. - **2** Syntax error in the command line. - **3** Fatal error: out of memory etc. ## NOTES The process name used for matching is limited to the 15 characters present in the output of /proc/*pid*/stat. Use the **-f** option to match against the complete command line, /proc/*pid*/cmdline. Threads may not have the same process name as the parent process but will have the same command line. The running **pgrep**, **pkill**, or **pidwait** process will never report itself as a match. The **-O --older** option will silently fail if */proc* is mounted with the *subset=pid* option. **pkill** will attempt to use [**pidfd\_send\_signal**(2)](/pidfd_send_signal/2.md) instead of [**kill**(2)](/kill/2.md) or [**sigqueue**(3)](/sigqueue/3.md) to send a signal to the target process if it is able to get the process file descriptor. ## BUGS The options **-n** and **-o** and **-v** can not be combined. Let me know if you need to do this. If processes start in the same clock tick (usually but not always a 100th of a second), the options **-n** and **-o** will not be able to distinguish which process started in the same clock tick and may give erroneous results. Defunct processes are reported. **pidwait** requires the [**pidfd\_open**(2)](/pidfd_open/2.md) system call which first appeared in Linux 5.3. ## SEE ALSO [**killall**(1)](/killall/1.md), [**kill**(1)](/kill/1.md), [**ps**(1)](/ps/1.md), [**skill**(1)](/skill/1.md), [**kill**(2)](/kill/2.md), [**sigaction**(2)](/sigaction/2.md), [**pidfd\_open**(2)](/pidfd_open/2.md), [**pidfd\_send\_signal**(2)](/pidfd_send_signal/2.md), [**sigqueue**(3)](/sigqueue/3.md), [**cgroups**(7)](/cgroups/7.md), [**regex**(7)](/regex/7.md), [**signal**(7)](/signal/7.md) ## REPORTING BUGS Please send bug reports to ⟨procps@freelists.org⟩.