.\" Copyright 1994 Salvatore Valente (svalente@mit.edu)
.\" Copyright 1992 Rickard E. Faith (faith@cs.unc.edu)
.\" May be distributed under the GNU General Public License
-.TH KILL 1 "July 2014" "util-linux" "User Commands"
+.TH KILL 1 "November 2019" "util-linux" "User Commands"
.SH NAME
kill \- terminate a process
.SH SYNOPSIS
.B kill
.RB [ \- \fIsignal\fR| \-s
-.IR signal | \fB-p\fP ]
+.IR signal | \fB\-p\fP ]
.RB [ \-q
.IR value ]
.RB [ \-a ]
+\fR[\fB\-\-timeout \fImilliseconds signal\fR]
.RB [ \-\- ]
.IR pid | name ...
.br
The command
.B kill
sends the specified \fIsignal\fR to the specified processes or process groups.
-If no signal is specified, the TERM signal is sent. This TERM signal will kill
-processes that do not catch it; for other processes it may be necessary to use
-the KILL signal (number 9), since this signal cannot be caught.
.PP
-Most modern shells have a builtin kill function, with a usage rather similar to
+If no signal is specified, the TERM signal is sent.
+The default action for this signal is to terminate the process.
+This signal should be used in preference to the
+KILL signal (number 9), since a process may install a handler for the
+TERM signal in order to perform clean-up steps before terminating in
+an orderly fashion.
+If a process does not terminate after a TERM signal has been sent,
+then the KILL signal may be used; be aware that the latter signal
+cannot be caught, and so does not give the target process the opportunity
+to perform any clean-up before terminating.
+.PP
+Most modern shells have a builtin kill command, with a usage rather similar to
that of the command described here. The
.BR \-\-all ,
.BR \-\-pid ", and"
-.BR \-\-queue
+.B \-\-queue
options, and the possibility to specify processes by command name, are local extensions.
.PP
If \fIsignal\fR is 0, then no actual signal is sent, but error checking is still performed.
.SH ARGUMENTS
-The list of processes to be signaled can be a mixture of names and pids.
+The list of processes to be signaled can be a mixture of names and PIDs.
.TP
.I pid
Each
.I n
where
.I n
-is larger than 0. The process with pid
+is larger than 0. The process with PID
.I n
is signaled.
.TP
.B 0
All processes in the current process group are signaled.
.TP
-.B -1
-All processes with a pid larger than 1 are signaled.
+.B \-1
+All processes with a PID larger than 1 are signaled.
.TP
-.BI - n
+.BI \- n
where
.I n
is larger than 1. All processes in process group
.I n
-are signaled. When an argument of the form '-n' is given, and it is meant to
+are signaled. When an argument of the form '\-n' is given, and it is meant to
denote a process group, either a signal must be specified first, or the
-argument must be preceded by a '--' option, otherwise it will be taken as the
+argument must be preceded by a '\-\-' option, otherwise it will be taken as the
signal to send.
.RE
.TP
numbers.
.TP
\fB\-a\fR, \fB\-\-all\fR
-Do not restrict the commandname-to-pid conversion to processes with the same
-uid as the present process.
+Do not restrict the command-name-to-PID conversion to processes with the same
+UID as the present process.
.TP
\fB\-p\fR, \fB\-\-pid\fR
-Only print the process id (pid) of the named processes, do not send any
+Only print the process ID (PID) of the named processes, do not send any
signals.
-.IP
-The \fB\-\-pid\fR option is automatically enabled when the \fBkill\fR command
-is invoked with the name of
-.BR pid .
-This functionality is deprecated, and will be removed in March 2016.
+.TP
+\fB\-\-verbose\fR
+Print PID(s) that will be signaled with kill along with the signal.
.TP
\fB\-q\fR, \fB\-\-queue\fR \fIvalue\fR
Use
-.BR sigqueue (2)
+.BR sigqueue (3)
rather than
.BR kill (2).
The
.I value
argument is an integer that is sent along with the signal. If the
-receiving process has installed a handler for this signal using the SA_SIGINFO
+receiving process has installed a handler for this signal using the
+.B SA_SIGINFO
flag to
.BR sigaction (2),
-then it can obtain this data via the si_sigval field of the siginfo_t structure.
-
-.SH NOTES
-It is not possible to send a signal to an explicitly selected thread in a
-multithreaded process using the
-.BR kill (2)
-syscall. If
-.BR kill(2)
-is used to send a signal to a thread group, then the kernel selects an arbitrary
-member of the thread group that has not blocked the signal. For more details
-see
-.BR clone (2),
-the CLONE_THREAD description.
-.PP
-The command
-.BR kill (1)
-as well as syscall
-.BR kill (2)
-accept a TID (thread ID, see
-.BR gettid (2))
-as an argument. In this case the kill behavior is not changed and the signal is
-also delivered to the thread group rather than to the specified thread.
-
-.SH RETURN CODES
+then it can obtain this data via the
+.I si_sigval
+field of the
+.I siginfo_t
+structure.
+.TP
+\fB\-\-timeout\fR \fImilliseconds signal\fR
+Send a signal defined the usual way to a process.
+.B \-\-timeout
+will make
+.B kill
+to wait for a period defined in
+.I milliseconds
+before sending follow-up
+.I signal
+to process.
+This feature is implemented by PID file-descriptor and guaranties that
+follow-up signals are sent to the same process or not sent if the process no
+more exist. Note that the operating system may re-use PIDs and implement the
+same feature in a shell by kill and sleep commands sequence may introduce a
+race. This option can be specified more than once than signals are sent
+sequentially in defined timeouts. The
+.B \-\-timeout
+option can be combined with
+.B \-\-queue
+option.
+.IP
+Example. Send signals QUIT, TERM and KILL in sequence and wait for 1000
+milliseconds between the signals
+.br
+kill \-\-verbose \-\-timeout 1000 TERM \-\-timeout 1000 KILL \-\-signal QUIT 12345
+.SH EXIT STATUS
.B kill
-has the following return codes:
+has the following exit status values:
+.PP
+.RS
+.PD 0
.TP
-.BR 0
+.B 0
success
.TP
-.BR 1
+.B 1
failure
.TP
-.BR 64
+.B 64
partial success (when more than one process specified)
-
-.SH SEE ALSO
-.BR bash (1),
-.BR tcsh (1),
-.BR kill (2),
-.BR sigvec (2),
+.PD
+.RE
+.SH NOTES
+Although it is possible to specify the TID (thread ID, see
+.BR gettid (2))
+of one of the threads in a multithreaded process as the argument of
+.BR kill ,
+the signal is nevertheless directed to the process
+(i.e., the entire thread group).
+In other words, it is not possible to send a signal to an
+explicitly selected thread in a multithreaded process.
+The signal will be delivered to an arbitrarily selected thread
+in the target process that is not blocking the signal.
+For more details, see
.BR signal (7)
-
+and the description of
+.B CLONE_THREAD
+in
+.BR clone (2).
+.P
+Various shells have provide an internal kill implementation that is
+preferred in relation to the
+.BR kill (1)
+executable described by this manual. Easiest way to ensure one is executing
+the executable is to use full path when calling the command, for example:
+.B "/bin/kill \-\-version"
.SH AUTHORS
.MT svalente@mit.edu
Salvatore Valente
.PP
The original version was taken from BSD 4.4.
+.SH SEE ALSO
+.BR bash (1),
+.BR tcsh (1),
+.BR sigaction (2),
+.BR kill (2),
+.BR sigqueue (3),
+.BR signal (7)
+
.SH AVAILABILITY
The kill command is part of the util-linux package and is available from
-.UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
+.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .
projects / thirdparty / util-linux.git / blobdiff