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
12
14 The command kill sends the specified signal to the specified processes
15 or process groups.
16 If no signal is specified, the TERM signal is sent. The default action
18 for this signal is to terminate the process. This signal should be
19 used in preference to the KILL signal (number 9), since a process may
20 install a handler for the TERM signal in order to perform clean-up
21 steps before terminating in an orderly fashion. If a process does not
22 terminate after a TERM signal has been sent, then the KILL signal may
23 be used; be aware that the latter signal cannot be caught, and so does
24 not give the target process the opportunity to perform any clean-up
25 before terminating.
26 Most modern shells have a builtin kill command, with a usage rather
28 similar to that of the command described here. The --all, --pid, and
29 --queue options, and the possibility to specify processes by command
30 name, are local extensions.
31 If signal is 0, then no actual signal is sent, but error checking is
33 still performed.
34
37 The list of processes to be signaled can be a mixture of names and
38 PIDs.
39 pid Each pid can be expressed in one of the following ways:
41 n where n is larger than 0. The process with PID n is sig‐
43 naled.
44 0 All processes in the current process group are signaled.
46 -1 All processes with a PID larger than 1 are signaled.
48 -n where n is larger than 1. All processes in process group
50 n are signaled. When an argument of the form '-n' is
51 given, and it is meant to denote a process group, either
52 a signal must be specified first, or the argument must be
53 preceded by a '--' option, otherwise it will be taken as
54 the signal to send.
55 name All processes invoked using this name will be signaled.
57
60 -s, --signal signal
61 The signal to send. It may be given as a name or a number.
62 -l, --list [number]
64 Print a list of signal names, or convert the given signal number
65 to a name. The signals can be found in /usr/include/linux/sig‐
66 nal.h.
67 -L, --table
69 Similar to -l, but it will print signal names and their corre‐
70 sponding numbers.
71 -a, --all
73 Do not restrict the command-name-to-PID conversion to processes
74 with the same UID as the present process.
75 -p, --pid
77 Only print the process ID (PID) of the named processes, do not
78 send any signals.
79 --verbose
81 Print PID(s) that will be signaled with kill along with the sig‐
82 nal.
83 -q, --queue value
85 Send the signal using sigqueue(3) rather than kill(2). The
86 value argument is an integer that is sent along with the signal.
87 If the receiving process has installed a handler for this signal
88 using the SA_SIGINFO flag to sigaction(2), then it can obtain
89 this data via the si_sigval field of the siginfo_t structure.
90 --timeout milliseconds signal
92 Send a signal defined in the usual way to a process, followed by
93 an additional signal after a specified delay. The --timeout
94 option causes kill to wait for a period defined in milliseconds
95 before sending a follow-up signal to the process. This feature
96 is implemented using the Linux kernel PID file descriptor fea‐
97 ture in order to guarantee that the follow-up signal is sent to
98 the same process or not sent if the process no longer exists.
99 Note that the operating system may re-use PIDs and implementing
101 an equivalent feature in a shell using kill and sleep would be
102 subject to races whereby the follow-up signal might be sent to a
103 different process that used a recycled PID.
104 The --timeout option can be specified multiple times: the sig‐
106 nals are sent sequentially with the specified timeouts. The
107 --timeout option can be combined with the --queue option.
108 As an example, the following command sends the signals QUIT,
110 TERM and KILL in sequence and waits for 1000 milliseconds
111 between sending the signals:
112 kill --verbose --timeout 1000 TERM --timeout 1000 KILL \
114 --signal QUIT 12345
115
117 kill has the following exit status values:
118 0 success
120 1 failure
121 64 partial success (when more than one process specified)
122
124 Although it is possible to specify the TID (thread ID, see gettid(2))
125 of one of the threads in a multithreaded process as the argument of
126 kill, the signal is nevertheless directed to the process (i.e., the
127 entire thread group). In other words, it is not possible to send a
128 signal to an explicitly selected thread in a multithreaded process.
129 The signal will be delivered to an arbitrarily selected thread in the
130 target process that is not blocking the signal. For more details, see
131 signal(7) and the description of CLONE_THREAD in clone(2).
132 Various shells provide a builtin kill command that is preferred in
134 relation to the kill(1) executable described by this manual. The easi‐
135 est way to ensure one is executing the command described in this page
136 is to use the full path when calling the command, for example:
137 /bin/kill --version
138
140 Salvatore Valente ⟨svalente@mit.edu⟩
141 Karel Zak ⟨kzak@redhat.com⟩
142 The original version was taken from BSD 4.4.
144
147 bash(1), tcsh(1), sigaction(2), kill(2), sigqueue(3), signal(7)
148
151 The kill command is part of the util-linux package and is available
152 from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
153 linux/⟩.
154util-linux November 2019 KILL(1)