1KILL(1) User Commands KILL(1)
2
6 kill - terminate a process
7
9 kill [-signal|-s signal|-p] [-q value] [-a] [--timeout milliseconds
10 signal] [--] pid|name...
11 kill -l [number] | -L
13
15 The command kill sends the specified signal to the specified processes
16 or process groups.
17 If no signal is specified, the TERM signal is sent. The default action
19 for this signal is to terminate the process. This signal should be used
20 in preference to the KILL signal (number 9), since a process may
21 install a handler for the TERM signal in order to perform clean-up
22 steps before terminating in an orderly fashion. If a process does not
23 terminate after a TERM signal has been sent, then the KILL signal may
24 be used; be aware that the latter signal cannot be caught, and so does
25 not give the target process the opportunity to perform any clean-up
26 before terminating.
27 Most modern shells have a builtin kill command, with a usage rather
29 similar to that of the command described here. The --all, --pid, and
30 --queue options, and the possibility to specify processes by command
31 name, are local extensions.
32 If signal is 0, then no actual signal is sent, but error checking is
34 still performed.
35
37 The list of processes to be signaled can be a mixture of names and
38 PIDs.
39 pid
41 Each pid can be expressed in one of the following ways:
42 n
44 where n is larger than 0. The process with PID n is signaled.
45 0
47 All processes in the current process group are signaled.
48 -1
50 All processes with a PID larger than 1 are signaled.
51 -n
53 where n is larger than 1. All processes in process group n are
54 signaled. When an argument of the form '-n' is given, and it is
55 meant to denote a process group, either a signal must be
56 specified first, or the argument must be preceded by a '--'
57 option, otherwise it will be taken as the signal to send.
58 name
60 All processes invoked using this name will be signaled.
61
63 -s, --signal signal
64 The signal to send. It may be given as a name or a number.
65 -l, --list [number]
67 Print a list of signal names, or convert the given signal number to
68 a name. The signals can be found in /usr/include/linux/signal.h.
69 -L, --table
71 Similar to -l, but it will print signal names and their
72 corresponding numbers.
73 -a, --all
75 Do not restrict the command-name-to-PID conversion to processes
76 with the same UID as the present process.
77 -p, --pid
79 Only print the process ID (PID) of the named processes, do not send
80 any signals.
81 -r, --require-handler
83 Do not send the signal if it is not caught in userspace by the
84 signalled process.
85 --verbose
87 Print PID(s) that will be signaled with kill along with the signal.
88 -q, --queue value
90 Send the signal using sigqueue(3) rather than kill(2). The value
91 argument is an integer that is sent along with the signal. If the
92 receiving process has installed a handler for this signal using the
93 SA_SIGINFO flag to sigaction(2), then it can obtain this data via
94 the si_sigval field of the siginfo_t structure.
95 --timeout milliseconds signal
97 Send a signal defined in the usual way to a process, followed by an
98 additional signal after a specified delay. The --timeout option
99 causes kill to wait for a period defined in milliseconds before
100 sending a follow-up signal to the process. This feature is
101 implemented using the Linux kernel PID file descriptor feature in
102 order to guarantee that the follow-up signal is sent to the same
103 process or not sent if the process no longer exists.
104 Note that the operating system may re-use PIDs and implementing an
106 equivalent feature in a shell using kill and sleep would be subject
107 to races whereby the follow-up signal might be sent to a different
108 process that used a recycled PID.
109 The --timeout option can be specified multiple times: the signals
111 are sent sequentially with the specified timeouts. The --timeout
112 option can be combined with the --queue option.
113 As an example, the following command sends the signals QUIT, TERM
115 and KILL in sequence and waits for 1000 milliseconds between
116 sending the signals:
117 kill --verbose --timeout 1000 TERM --timeout 1000 KILL \
119 --signal QUIT 12345
120
122 kill has the following exit status values:
123 0
125 success
126 1
128 failure
129 64
131 partial success (when more than one process specified)
132
134 Although it is possible to specify the TID (thread ID, see gettid(2))
135 of one of the threads in a multithreaded process as the argument of
136 kill, the signal is nevertheless directed to the process (i.e., the
137 entire thread group). In other words, it is not possible to send a
138 signal to an explicitly selected thread in a multithreaded process. The
139 signal will be delivered to an arbitrarily selected thread in the
140 target process that is not blocking the signal. For more details, see
141 signal(7) and the description of CLONE_THREAD in clone(2).
142 Various shells provide a builtin kill command that is preferred in
144 relation to the kill(1) executable described by this manual. The
145 easiest way to ensure one is executing the command described in this
146 page is to use the full path when calling the command, for example:
147 /bin/kill --version
148
150 Salvatore Valente <svalente@mit.edu>, Karel Zak <kzak@redhat.com>
151 The original version was taken from BSD 4.4.
153
155 bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7)
156
158 For bug reports, use the issue tracker at
159 https://github.com/util-linux/util-linux/issues.
160
162 The kill command is part of the util-linux package which can be
163 downloaded from Linux Kernel Archive
164 <https://www.kernel.org/pub/linux/utils/util-linux/>.
165util-linux 2.39.2 2023-06-14 KILL(1)