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
12 kill - terminate or signal processes
13
15 kill -s signal_name pid ...
16 kill -l [exit_status]
18 kill [-signal_name] pid ...
22 kill [-signal_number] pid ...
24
27 The kill utility shall send a signal to the process or processes speci‐
28 fied by each pid operand.
29 For each pid operand, the kill utility shall perform actions equivalent
31 to the kill() function defined in the System Interfaces volume of
32 IEEE Std 1003.1-2001 called with the following arguments:
33 * The value of the pid operand shall be used as the pid argument.
35 * The sig argument is the value specified by the -s option, - sig‐
37 nal_number option, or the - signal_name option, or by SIGTERM, if
38 none of these options is specified.
39
41 The kill utility shall conform to the Base Definitions volume of
42 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines, except
43 that in the last two SYNOPSIS forms, the - signal_number and - sig‐
44 nal_name options are usually more than a single character.
45 The following options shall be supported:
47 -l (The letter ell.) Write all values of signal_name supported by
49 the implementation, if no operand is given. If an exit_status
50 operand is given and it is a value of the '?' shell special
51 parameter (see Special Parameters and wait() ) corresponding to
52 a process that was terminated by a signal, the signal_name cor‐
53 responding to the signal that terminated the process shall be
54 written. If an exit_status operand is given and it is the
55 unsigned decimal integer value of a signal number, the sig‐
56 nal_name (the symbolic constant name without the SIG prefix
57 defined in the Base Definitions volume of IEEE Std 1003.1-2001)
58 corresponding to that signal shall be written. Otherwise, the
59 results are unspecified.
60 -s signal_name
62 Specify the signal to send, using one of the symbolic names
64 defined in the <signal.h> header. Values of signal_name shall be
65 recognized in a case-independent fashion, without the SIG pre‐
66 fix. In addition, the symbolic name 0 shall be recognized, rep‐
67 resenting the signal value zero. The corresponding signal shall
68 be sent instead of SIGTERM.
69 -signal_name
71 Equivalent to -s signal_name.
73 -signal_number
75 Specify a non-negative decimal integer, signal_number, repre‐
77 senting the signal to be used instead of SIGTERM, as the sig
78 argument in the effective call to kill(). The correspondence
79 between integer values and the sig value used is shown in the
80 following table.
81 The effects of specifying any signal_number other than those listed in
83 the table are undefined.
84 signal_number sig Value
88 0 0
89 1 SIGHUP
90 2 SIGINT
91 3 SIGQUIT
92 6 SIGABRT
93 9 SIGKILL
94 14 SIGALRM
95 15 SIGTERM
96 If the first argument is a negative integer, it shall be interpreted as
98 a - signal_number option, not as a negative pid operand specifying a
99 process group.
100
102 The following operands shall be supported:
103 pid One of the following:
105 1. A decimal integer specifying a process or process group to
107 be signaled. The process or processes selected by positive,
108 negative, and zero values of the pid operand shall be as
109 described for the kill() function. If process number 0 is
110 specified, all processes in the current process group shall
111 be signaled. For the effects of negative pid numbers, see
112 the kill() function defined in the System Interfaces volume
113 of IEEE Std 1003.1-2001. If the first pid operand is nega‐
114 tive, it should be preceded by "--" to keep it from being
115 interpreted as an option.
116 2. A job control job ID (see the Base Definitions volume of
118 IEEE Std 1003.1-2001, Section 3.203, Job Control Job ID)
119 that identifies a background process group to be signaled.
120 The job control job ID notation is applicable only for invo‐
121 cations of kill in the current shell execution environment;
122 see Shell Execution Environment .
123 exit_status
125 A decimal integer specifying a signal number or the exit status
126 of a process terminated by a signal.
127
130 Not used.
131
133 None.
134
136 The following environment variables shall affect the execution of kill:
137 LANG Provide a default value for the internationalization variables
139 that are unset or null. (See the Base Definitions volume of
140 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
141 ables for the precedence of internationalization variables used
142 to determine the values of locale categories.)
143 LC_ALL If set to a non-empty string value, override the values of all
145 the other internationalization variables.
146 LC_CTYPE
148 Determine the locale for the interpretation of sequences of
149 bytes of text data as characters (for example, single-byte as
150 opposed to multi-byte characters in arguments).
151 LC_MESSAGES
153 Determine the locale that should be used to affect the format
154 and contents of diagnostic messages written to standard error.
155 NLSPATH
157 Determine the location of message catalogs for the processing of
158 LC_MESSAGES .
159
162 Default.
163
165 When the -l option is not specified, the standard output shall not be
166 used.
167 When the -l option is specified, the symbolic name of each signal shall
169 be written in the following format:
170 "%s%c", <signal_name>, <separator>
173 where the <signal_name> is in uppercase, without the SIG prefix, and
175 the <separator> shall be either a <newline> or a <space>. For the last
176 signal written, <separator> shall be a <newline>.
177 When both the -l option and exit_status operand are specified, the sym‐
179 bolic name of the corresponding signal shall be written in the follow‐
180 ing format:
181 "%s\n", <signal_name>
184
186 The standard error shall be used only for diagnostic messages.
187
189 None.
190
192 None.
193
195 The following exit values shall be returned:
196 0 At least one matching process was found for each pid operand,
198 and the specified signal was successfully processed for at least
199 one matching process.
200 >0 An error occurred.
202
205 Default.
206 The following sections are informative.
208
210 Process numbers can be found by using ps.
211 The job control job ID notation is not required to work as expected
213 when kill is operating in its own utility execution environment. In
214 either of the following examples:
215 nohup kill %1 &
218 system("kill %1");
219 the kill operates in a different environment and does not share the
221 shell's understanding of job numbers.
222
224 Any of the commands:
225 kill -9 100 -165
228 kill -s kill 100 -165
229 kill -s KILL 100 -165
230 sends the SIGKILL signal to the process whose process ID is 100 and to
232 all processes whose process group ID is 165, assuming the sending
233 process has permission to send that signal to the specified processes,
234 and that they exist.
235 The System Interfaces volume of IEEE Std 1003.1-2001 and this volume of
237 IEEE Std 1003.1-2001 do not require specific signal numbers for any
238 signal_names. Even the - signal_number option provides symbolic
239 (although numeric) names for signals. If a process is terminated by a
240 signal, its exit status indicates the signal that killed it, but the
241 exact values are not specified. The kill -l option, however, can be
242 used to map decimal signal numbers and exit status values into the name
243 of a signal. The following example reports the status of a terminated
244 job:
245 job
248 stat=$?
249 if [ $stat -eq 0 ]
250 then
251 echo job completed successfully.
252 elif [ $stat -gt 128 ]
253 then
254 echo job terminated by signal SIG$(kill -l $stat).
255 else
256 echo job terminated with error code $stat.
257 fi
258 To send the default signal to a process group (say 123), an application
260 should use a command similar to one of the following:
261 kill -TERM -123
264 kill -- -123
265
267 The -l option originated from the C shell, and is also implemented in
268 the KornShell. The C shell output can consist of multiple output lines
269 because the signal names do not always fit on a single line on some
270 terminal screens. The KornShell output also included the implementa‐
271 tion-defined signal numbers and was considered by the standard develop‐
272 ers to be too difficult for scripts to parse conveniently. The speci‐
273 fied output format is intended not only to accommodate the historical C
274 shell output, but also to permit an entirely vertical or entirely hori‐
275 zontal listing on systems for which this is appropriate.
276 An early proposal invented the name SIGNULL as a signal_name for signal
278 0 (used by the System Interfaces volume of IEEE Std 1003.1-2001 to test
279 for the existence of a process without sending it a signal). Since the
280 signal_name 0 can be used in this case unambiguously, SIGNULL has been
281 removed.
282 An early proposal also required symbolic signal_names to be recognized
284 with or without the SIG prefix. Historical versions of kill have not
285 written the SIG prefix for the -l option and have not recognized the
286 SIG prefix on signal_names. Since neither applications portability nor
287 ease-of-use would be improved by requiring this extension, it is no
288 longer required.
289 To avoid an ambiguity of an initial negative number argument specifying
291 either a signal number or a process group, IEEE Std 1003.1-2001 man‐
292 dates that it is always considered the former by implementations that
293 support the XSI option. It also requires that conforming applications
294 always use the "--" options terminator argument when specifying a
295 process group, unless an option is also specified.
296 The -s option was added in response to international interest in pro‐
298 viding some form of kill that meets the Utility Syntax Guidelines.
299 The job control job ID notation is not required to work as expected
301 when kill is operating in its own utility execution environment. In
302 either of the following examples:
303 nohup kill %1 &
306 system("kill %1");
307 the kill operates in a different environment and does not understand
309 how the shell has managed its job numbers.
310
312 None.
313
315 Shell Command Language, ps, wait(), the System Interfaces volume of
316 IEEE Std 1003.1-2001, kill(), the Base Definitions volume of
317 IEEE Std 1003.1-2001, <signal.h>
318
320 Portions of this text are reprinted and reproduced in electronic form
321 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
322 -- Portable Operating System Interface (POSIX), The Open Group Base
323 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
324 Electrical and Electronics Engineers, Inc and The Open Group. In the
325 event of any discrepancy between this version and the original IEEE and
326 The Open Group Standard, the original IEEE and The Open Group Standard
327 is the referee document. The original Standard can be obtained online
328 at http://www.opengroup.org/unix/online.html .
329IEEE/The Open Group 2003 KILL(1P)