Section: User Commands (1)
Updated: 2020-06-04
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pgrep, pkill, pidwait - look up, signal, or wait for processes based on name and other attributes  


pgrep [options] pattern
pkill [options] pattern
pidwait [options] pattern  


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 called 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.  


--signal signal Defines the signal to send to each matched process. Either the numeric or the symbolic signal name can be used. (pkill only.)
-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.
-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.
-i, --ignore-case
Match processes case-insensitively.
-l, --list-name
List the process name as well as the process ID. (pgrep only.)
-a, --list-full
List the full command line as well as the process ID. (pgrep only.)
-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, --parent ppid,...
Only match processes whose parent process ID is listed.
-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.
-F, --pidfile file
Read PIDs from file. This option is more useful for pkillorpidwait than pgrep.
-L, --logpidfile
Fail if pidfile (see -F) not locked.
-r, --runstates D,R,S,Z,...
Match only processes which match the process state.
--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.
-q, --queue value
Use sigqueue(3) rather than kill(2) and the value argument is used to specify an integer to be sent with the signal. If the receiving process has installed a handler for this signal using the SA_SIGINFO flag to sigaction(2) , then it can obtain this data via the si_value field of the siginfo_t structure.
-V, --version
Display version information and exit.
-h, --help
Display help and exit.


Specifies an Extended Regular Expression for matching against the process names or command lines.


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 xterm processes:

$ ps -fp $(pgrep -d, -x xterm)

Example 4: Make all chrome processes run nicer:

$ renice +4 $(pgrep chrome)


One or more processes matched the criteria. For pkill and pidwait, one or more processes must also have been successfully signalled or waited for.
No processes matched or none of them could be signalled.
Syntax error in the command line.
Fatal error: out of memory etc.


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.

The running pgrep, pkill, or pidwait process will never report itself as a match.  


The options -n and -o and -v can not be combined. Let me know if you need to do this.

Defunct processes are reported.



ps(1), regex(7), signal(7), sigqueue(3), killall(1), skill(1), kill(1), kill(2)  


Kjetil Torgrim Homme  


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