1KILL(1P) POSIX Programmer's Manual KILL(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 kill — terminate or signal processes
14
16 kill −s signal_name pid...
17 kill −l [exit_status]
19 kill [−signal_name] pid...
21 kill [−signal_number] pid...
23
25 The kill utility shall send a signal to the process or processes speci‐
26 fied by each pid operand.
27 For each pid operand, the kill utility shall perform actions equivalent
29 to the kill() function defined in the System Interfaces volume of
30 POSIX.1‐2008 called with the following arguments:
31 * The value of the pid operand shall be used as the pid argument.
33 * The sig argument is the value specified by the −s option, −sig‐
35 nal_number option, or the −signal_name option, or by SIGTERM, if
36 none of these options is specified.
37
39 The kill utility shall conform to the Base Definitions volume of
40 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that in
41 the last two SYNOPSIS forms, the −signal_number and −signal_name
42 options are usually more than a single character.
43 The following options shall be supported:
45 −l (The letter ell.) Write all values of signal_name supported
47 by the implementation, if no operand is given. If an
48 exit_status operand is given and it is a value of the '?'
49 shell special parameter (see Section 2.5.2, Special Parame‐
50 ters and wait) corresponding to a process that was terminated
51 by a signal, the signal_name corresponding to the signal that
52 terminated the process shall be written. If an exit_status
53 operand is given and it is the unsigned decimal integer value
54 of a signal number, the signal_name (the symbolic constant
55 name without the SIG prefix defined in the Base Definitions
56 volume of POSIX.1‐2008) corresponding to that signal shall be
57 written. Otherwise, the results are unspecified.
58 −s signal_name
60 Specify the signal to send, using one of the symbolic names
61 defined in the <signal.h> header. Values of signal_name shall
62 be recognized in a case-independent fashion, without the SIG
63 prefix. In addition, the symbolic name 0 shall be recognized,
64 representing the signal value zero. The corresponding signal
65 shall be sent instead of SIGTERM.
66 −signal_name
68 Equivalent to −s signal_name.
69 −signal_number
71 Specify a non-negative decimal integer, signal_number, repre‐
72 senting the signal to be used instead of SIGTERM, as the sig
73 argument in the effective call to kill(). The correspondence
74 between integer values and the sig value used is shown in the
75 following list.
76 The effects of specifying any signal_number other than those
78 listed below are undefined.
79 0 0
81 1 SIGHUP
83 2 SIGINT
85 3 SIGQUIT
87 6 SIGABRT
89 9 SIGKILL
91 14 SIGALRM
93 15 SIGTERM
95 If the first argument is a negative integer, it shall be
97 interpreted as a −signal_number option, not as a negative pid
98 operand specifying a process group.
99
101 The following operands shall be supported:
102 pid One of the following:
104 1. A decimal integer specifying a process or process group
106 to be signaled. The process or processes selected by
107 positive, negative, and zero values of the pid operand
108 shall be as described for the kill() function. If process
109 number 0 is specified, all processes in the current
110 process group shall be signaled. For the effects of nega‐
111 tive pid numbers, see the kill() function defined in the
112 System Interfaces volume of POSIX.1‐2008. If the first
113 pid operand is negative, it should be preceded by "−−" to
114 keep it from being interpreted as an option.
115 2. A job control job ID (see the Base Definitions volume of
117 POSIX.1‐2008, Section 3.204, Job Control Job ID) that
118 identifies a background process group to be signaled. The
119 job control job ID notation is applicable only for invo‐
120 cations of kill in the current shell execution environ‐
121 ment; see Section 2.12, Shell Execution Environment.
122 exit_status
124 A decimal integer specifying a signal number or the exit sta‐
125 tus of a process terminated by a signal.
126
128 Not used.
129
131 None.
132
134 The following environment variables shall affect the execution of kill:
135 LANG Provide a default value for the internationalization vari‐
137 ables that are unset or null. (See the Base Definitions vol‐
138 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
139 ables for the precedence of internationalization variables
140 used to determine the values of locale categories.)
141 LC_ALL If set to a non-empty string value, override the values of
143 all the other internationalization variables.
144 LC_CTYPE Determine the locale for the interpretation of sequences of
146 bytes of text data as characters (for example, single-byte as
147 opposed to multi-byte characters in arguments).
148 LC_MESSAGES
150 Determine the locale that should be used to affect the format
151 and contents of diagnostic messages written to standard
152 error.
153 NLSPATH Determine the location of message catalogs for the processing
155 of LC_MESSAGES.
156
158 Default.
159
161 When the −l option is not specified, the standard output shall not be
162 used.
163 When the −l option is specified, the symbolic name of each signal shall
165 be written in the following format:
166 "%s%c", <signal_name>, <separator>
168 where the <signal_name> is in uppercase, without the SIG prefix, and
170 the <separator> shall be either a <newline> or a <space>. For the last
171 signal written, <separator> shall be a <newline>.
172 When both the −l option and exit_status operand are specified, the sym‐
174 bolic name of the corresponding signal shall be written in the follow‐
175 ing format:
176 "%s\n", <signal_name>
178
180 The standard error shall be used only for diagnostic messages.
181
183 None.
184
186 None.
187
189 The following exit values shall be returned:
190 0 At least one matching process was found for each pid operand, and
192 the specified signal was successfully processed for at least one
193 matching process.
194 >0 An error occurred.
196
198 Default.
199 The following sections are informative.
201
203 Process numbers can be found by using ps.
204 The job control job ID notation is not required to work as expected
206 when kill is operating in its own utility execution environment. In
207 either of the following examples:
208 nohup kill %1 &
210 system("kill %1");
211 the kill operates in a different environment and does not share the
213 shell's understanding of job numbers.
214
216 Any of the commands:
217 kill −9 100 −165
219 kill −s kill 100 −165
220 kill −s KILL 100 −165
221 sends the SIGKILL signal to the process whose process ID is 100 and to
223 all processes whose process group ID is 165, assuming the sending
224 process has permission to send that signal to the specified processes,
225 and that they exist.
226 The System Interfaces volume of POSIX.1‐2008 and this volume of
228 POSIX.1‐2008 do not require specific signal numbers for any sig‐
229 nal_names. Even the −signal_number option provides symbolic (although
230 numeric) names for signals. If a process is terminated by a signal, its
231 exit status indicates the signal that killed it, but the exact values
232 are not specified. The kill −l option, however, can be used to map dec‐
233 imal signal numbers and exit status values into the name of a signal.
234 The following example reports the status of a terminated job:
235 job
237 stat=$?
238 if [ $stat −eq 0 ]
239 then
240 echo job completed successfully.
241 elif [ $stat −gt 128 ]
242 then
243 echo job terminated by signal SIG$(kill −l $stat).
244 else
245 echo job terminated with error code $stat.
246 fi
247 To send the default signal to a process group (say 123), an application
249 should use a command similar to one of the following:
250 kill −TERM −123
252 kill −− −123
253
255 The −l option originated from the C shell, and is also implemented in
256 the KornShell. The C shell output can consist of multiple output lines
257 because the signal names do not always fit on a single line on some
258 terminal screens. The KornShell output also included the implementa‐
259 tion-defined signal numbers and was considered by the standard develop‐
260 ers to be too difficult for scripts to parse conveniently. The speci‐
261 fied output format is intended not only to accommodate the historical C
262 shell output, but also to permit an entirely vertical or entirely hori‐
263 zontal listing on systems for which this is appropriate.
264 An early proposal invented the name SIGNULL as a signal_name for signal
266 0 (used by the System Interfaces volume of POSIX.1‐2008 to test for the
267 existence of a process without sending it a signal). Since the sig‐
268 nal_name 0 can be used in this case unambiguously, SIGNULL has been
269 removed.
270 An early proposal also required symbolic signal_names to be recognized
272 with or without the SIG prefix. Historical versions of kill have not
273 written the SIG prefix for the −l option and have not recognized the
274 SIG prefix on signal_names. Since neither applications portability nor
275 ease-of-use would be improved by requiring this extension, it is no
276 longer required.
277 To avoid an ambiguity of an initial negative number argument specifying
279 either a signal number or a process group, POSIX.1‐2008 mandates that
280 it is always considered the former by implementations that support the
281 XSI option. It also requires that conforming applications always use
282 the "−−" options terminator argument when specifying a process group,
283 unless an option is also specified.
284 The −s option was added in response to international interest in pro‐
286 viding some form of kill that meets the Utility Syntax Guidelines.
287 The job control job ID notation is not required to work as expected
289 when kill is operating in its own utility execution environment. In
290 either of the following examples:
291 nohup kill %1 &
293 system("kill %1");
294 the kill operates in a different environment and does not understand
296 how the shell has managed its job numbers.
297
299 None.
300
302 Chapter 2, Shell Command Language, ps, wait
303 The Base Definitions volume of POSIX.1‐2008, Section 3.204, Job Control
305 Job ID, Chapter 8, Environment Variables, Section 12.2, Utility Syntax
306 Guidelines, <signal.h>
307 The System Interfaces volume of POSIX.1‐2008, kill()
309
311 Portions of this text are reprinted and reproduced in electronic form
312 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
313 -- Portable Operating System Interface (POSIX), The Open Group Base
314 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
315 cal and Electronics Engineers, Inc and The Open Group. (This is
316 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
317 event of any discrepancy between this version and the original IEEE and
318 The Open Group Standard, the original IEEE and The Open Group Standard
319 is the referee document. The original Standard can be obtained online
320 at http://www.unix.org/online.html .
321 Any typographical or formatting errors that appear in this page are
323 most likely to have been introduced during the conversion of the source
324 files to man page format. To report such errors, see https://www.ker‐
325 nel.org/doc/man-pages/reporting_bugs.html .
326IEEE/The Open Group 2013 KILL(1P)