1signal.h(0P) POSIX Programmer's Manual signal.h(0P)
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 signal.h — signals
14
16 #include <signal.h>
17
19 Some of the functionality described on this reference page extends the
20 ISO C standard. Applications shall define the appropriate feature test
21 macro (see the System Interfaces volume of POSIX.1‐2008, Section 2.2,
22 The Compilation Environment) to enable the visibility of these symbols
23 in this header.
24 The <signal.h> header shall define the following macros, which shall
26 expand to constant expressions with distinct values that have a type
27 compatible with the second argument to, and the return value of, the
28 signal() function, and whose values shall compare unequal to the
29 address of any declarable function.
30 SIG_DFL Request for default signal handling.
32 SIG_ERR Return value from signal() in case of error.
34 SIG_HOLD Request that signal be held.
36 SIG_IGN Request that signal be ignored.
38 The <signal.h> header shall define the pthread_t, size_t, and uid_t
40 types as described in <sys/types.h>.
41 The <signal.h> header shall define the timespec structure as described
43 in <time.h>.
44 The <signal.h> header shall define the following data types:
46 sig_atomic_t Possibly volatile-qualified integer type of an object
48 that can be accessed as an atomic entity, even in the
49 presence of asynchronous interrupts.
50 sigset_t Integer or structure type of an object used to represent
52 sets of signals.
53 pid_t As described in <sys/types.h>.
55 The <signal.h> header shall define the pthread_attr_t type as described
57 in <sys/types.h>.
58 The <signal.h> header shall define the sigevent structure, which shall
60 include at least the following members:
61 int sigev_notify Notification type.
63 int sigev_signo Signal number.
64 union sigval sigev_value Signal value.
65 void (*sigev_notify_function)(union sigval)
66 Notification function.
67 pthread_attr_t *sigev_notify_attributes Notification attributes.
68 The <signal.h> header shall define the following symbolic constants for
70 the values of sigev_notify:
71 SIGEV_NONE No asynchronous notification is delivered when the event
73 of interest occurs.
74 SIGEV_SIGNAL A queued signal, with an application-defined value, is
76 generated when the event of interest occurs.
77 SIGEV_THREAD A notification function is called to perform notifica‐
79 tion.
80 The sigval union shall be defined as:
82 int sival_int Integer signal value.
84 void *sival_ptr Pointer signal value.
85 The <signal.h> header shall declare the SIGRTMIN and SIGRTMAX macros,
87 which shall expand to positive integer expressions with type int, but
88 which need not be constant expressions. These macros specify a range of
89 signal numbers that are reserved for application use and for which the
90 realtime signal behavior specified in this volume of POSIX.1‐2008 is
91 supported. The signal numbers in this range do not overlap any of the
92 signals specified in the following table.
93 The range SIGRTMIN through SIGRTMAX inclusive shall include at least
95 {RTSIG_MAX} signal numbers.
96 It is implementation-defined whether realtime signal behavior is sup‐
98 ported for other signals.
99 The <signal.h> header shall define the following macros that are used
101 to refer to the signals that occur in the system. Signals defined here
102 begin with the letters SIG followed by an uppercase letter. The macros
103 shall expand to positive integer constant expressions with type int and
104 distinct values. The value 0 is reserved for use as the null signal
105 (see kill()). Additional implementation-defined signals may occur in
106 the system.
107 The ISO C standard only requires the signal names SIGABRT, SIGFPE, SIG‐
109 ILL, SIGINT, SIGSEGV, and SIGTERM to be defined.
110 The following signals shall be supported on all implementations
112 (default actions are explained below the table):
113 ┌──────────┬────────────────┬────────────────────────────────────────────────────┐
115 │ Signal │ Default Action │ Description │
116 ├──────────┼────────────────┼────────────────────────────────────────────────────┤
117 │SIGABRT │ A │ Process abort signal. │
118 │SIGALRM │ T │ Alarm clock. │
119 │SIGBUS │ A │ Access to an undefined portion of a memory object. │
120 │SIGCHLD │ I │ Child process terminated, stopped, │
121 │ │ │ or continued. │
122 │SIGCONT │ C │ Continue executing, if stopped. │
123 │SIGFPE │ A │ Erroneous arithmetic operation. │
124 │SIGHUP │ T │ Hangup. │
125 │SIGILL │ A │ Illegal instruction. │
126 │SIGINT │ T │ Terminal interrupt signal. │
127 │SIGKILL │ T │ Kill (cannot be caught or ignored). │
128 │SIGPIPE │ T │ Write on a pipe with no one to read it. │
129 │SIGQUIT │ A │ Terminal quit signal. │
130 │SIGSEGV │ A │ Invalid memory reference. │
131 │SIGSTOP │ S │ Stop executing (cannot be caught or ignored). │
132 │SIGTERM │ T │ Termination signal. │
133 │SIGTSTP │ S │ Terminal stop signal. │
134 │SIGTTIN │ S │ Background process attempting read. │
135 │SIGTTOU │ S │ Background process attempting write. │
136 │SIGUSR1 │ T │ User-defined signal 1. │
137 │SIGUSR2 │ T │ User-defined signal 2. │
138 │SIGPOLL │ T │ Pollable event. │
139 │SIGPROF │ T │ Profiling timer expired. │
140 │SIGSYS │ A │ Bad system call. │
141 │SIGTRAP │ A │ Trace/breakpoint trap. │
142 │SIGURG │ I │ High bandwidth data is available at a socket. │
143 │SIGVTALRM │ T │ Virtual timer expired. │
144 │SIGXCPU │ A │ CPU time limit exceeded. │
145 │SIGXFSZ │ A │ File size limit exceeded. │
146 │ │ │ │
147 └──────────┴────────────────┴────────────────────────────────────────────────────┘
148 The default actions are as follows:
149 T Abnormal termination of the process.
151 A Abnormal termination of the process with additional actions.
153 I Ignore the signal.
155 S Stop the process.
157 C Continue the process, if it is stopped; otherwise, ignore the
159 signal.
160 The effects on the process in each case are described in the System
162 Interfaces volume of POSIX.1‐2008, Section 2.4.3, Signal Actions.
163 The <signal.h> header shall declare the sigaction structure, which
165 shall include at least the following members:
166 void (*sa_handler)(int) Pointer to a signal-catching function
168 or one of the SIG_IGN or SIG_DFL.
169 sigset_t sa_mask Set of signals to be blocked during execution
170 of the signal handling function.
171 int sa_flags Special flags.
172 void (*sa_sigaction)(int, siginfo_t *, void *)
173 Pointer to a signal-catching function.
174 The storage occupied by sa_handler and sa_sigaction may overlap, and a
176 conforming application shall not use both simultaneously.
177 The <signal.h> header shall define the following macros which shall
179 expand to integer constant expressions that need not be usable in #if
180 preprocessing directives:
181 SIG_BLOCK The resulting set is the union of the current set and the
183 signal set pointed to by the argument set.
184 SIG_UNBLOCK The resulting set is the intersection of the current set
186 and the complement of the signal set pointed to by the
187 argument set.
188 SIG_SETMASK The resulting set is the signal set pointed to by the
190 argument set.
191 The <signal.h> header shall also define the following symbolic con‐
193 stants:
194 SA_NOCLDSTOP Do not generate SIGCHLD when children stop
196 or stopped children continue.
197 SA_ONSTACK Causes signal delivery to occur on an alternate stack.
199 SA_RESETHAND Causes signal dispositions to be set to SIG_DFL on entry
201 to signal handlers.
202 SA_RESTART Causes certain functions to become restartable.
204 SA_SIGINFO Causes extra information to be passed to signal handlers
206 at the time of receipt of a signal.
207 SA_NOCLDWAIT Causes implementations not to create zombie processes on
209 child death.
210 SA_NODEFER Causes signal not to be automatically blocked on entry to
212 signal handler.
213 SS_ONSTACK Process is executing on an alternate signal stack.
215 SS_DISABLE Alternate signal stack is disabled.
217 MINSIGSTKSZ Minimum stack size for a signal handler.
219 SIGSTKSZ Default size in bytes for the alternate signal stack.
221 The <signal.h> header shall define the mcontext_t type through typedef.
223 The <signal.h> header shall define the ucontext_t type as a structure
225 that shall include at least the following members:
226 ucontext_t *uc_link Pointer to the context that is resumed
228 when this context returns.
229 sigset_t uc_sigmask The set of signals that are blocked when this
230 context is active.
231 stack_t uc_stack The stack used by this context.
232 mcontext_t uc_mcontext A machine-specific representation of the saved
233 context.
234 The <signal.h> header shall define the stack_t type as a structure,
236 which shall include at least the following members:
237 void *ss_sp Stack base or pointer.
239 size_t ss_size Stack size.
240 int ss_flags Flags.
241 The <signal.h> header shall define the siginfo_t type as a structure,
243 which shall include at least the following members:
244 int si_signo Signal number.
246 int si_code Signal code.
247 int si_errno If non-zero, an errno value associated with
248 this signal, as described in <errno.h>.
249 pid_t si_pid Sending process ID.
250 uid_t si_uid Real user ID of sending process.
251 void *si_addr Address of faulting instruction.
252 int si_status Exit value or signal.
253 long si_band Band event for SIGPOLL.
254 union sigval si_value Signal value.
255 The <signal.h> header shall define the symbolic constants in the Code
257 column of the following table for use as values of si_code that are
258 signal-specific or non-signal-specific reasons why the signal was gen‐
259 erated.
260┌───────┬─────────────┬──────────────────────────────────────────────────────────────────┐
262│Signal │ Code │ Reason │
263├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
264│SIGILL │ILL_ILLOPC │Illegal opcode. │
265│ │ILL_ILLOPN │Illegal operand. │
266│ │ILL_ILLADR │Illegal addressing mode. │
267│ │ILL_ILLTRP │Illegal trap. │
268│ │ILL_PRVOPC │Privileged opcode. │
269│ │ILL_PRVREG │Privileged register. │
270│ │ILL_COPROC │Coprocessor error. │
271│ │ILL_BADSTK │Internal stack error. │
272├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
273│SIGFPE │FPE_INTDIV │Integer divide by zero. │
274│ │FPE_INTOVF │Integer overflow. │
275│ │FPE_FLTDIV │Floating-point divide by zero. │
276│ │FPE_FLTOVF │Floating-point overflow. │
277│ │FPE_FLTUND │Floating-point underflow. │
278│ │FPE_FLTRES │Floating-point inexact result. │
279│ │FPE_FLTINV │Invalid floating-point operation. │
280│ │FPE_FLTSUB │Subscript out of range. │
281├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
282│SIGSEGV│SEGV_MAPERR │Address not mapped to object. │
283│ │SEGV_ACCERR │Invalid permissions for mapped object. │
284├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
285│SIGBUS │BUS_ADRALN │Invalid address alignment. │
286│ │BUS_ADRERR │Nonexistent physical address. │
287│ │BUS_OBJERR │Object-specific hardware error. │
288├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
289│SIGTRAP│TRAP_BRKPT │Process breakpoint. │
290│ │TRAP_TRACE │Process trace trap. │
291├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
292│SIGCHLD│CLD_EXITED │Child has exited. │
293│ │CLD_KILLED │Child has terminated abnormally and did not create a core file. │
294│ │CLD_DUMPED │Child has terminated abnormally and created a core file. │
295│ │CLD_TRAPPED │Traced child has trapped. │
296│ │CLD_STOPPED │Child has stopped. │
297│ │CLD_CONTINUED│Stopped child has continued. │
298├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
299│SIGPOLL│POLL_IN │Data input available. │
300│ │POLL_OUT │Output buffers available. │
301│ │POLL_MSG │Input message available. │
302│ │POLL_ERR │I/O error. │
303│ │POLL_PRI │High priority input available. │
304│ │POLL_HUP │Device disconnected. │
305├───────┼─────────────┼──────────────────────────────────────────────────────────────────┤
306│Any │SI_USER │Signal sent by kill(). │
307│ │SI_QUEUE │Signal sent by sigqueue(). │
308│ │SI_TIMER │Signal generated by expiration of a timer set by timer_settime(). │
309│ │SI_ASYNCIO │Signal generated by completion of an asynchronous I/O │
310│ │ │request. │
311│ │SI_MESGQ │Signal generated by arrival of a message on an empty message │
312│ │ │queue. │
313└───────┴─────────────┴──────────────────────────────────────────────────────────────────┘
314 Implementations may support additional si_code values not included in
315 this list, may generate values included in this list under circum‐
316 stances other than those described in this list, and may contain exten‐
317 sions or limitations that prevent some values from being generated.
318 Implementations do not generate a different value from the ones
319 described in this list for circumstances described in this list.
320 In addition, the following signal-specific information shall be avail‐
322 able:
323 ┌────────┬────────────────┬───────────────────────────────────────────────────┐
325 │Signal │ Member │ Value │
326 ├────────┼────────────────┼───────────────────────────────────────────────────┤
327 │SIGILL │ void * si_addr │ Address of faulting instruction. │
328 │SIGFPE │ │ │
329 ├────────┼────────────────┼───────────────────────────────────────────────────┤
330 │SIGSEGV │ void * si_addr │ Address of faulting memory reference. │
331 │SIGBUS │ │ │
332 ├────────┼────────────────┼───────────────────────────────────────────────────┤
333 │SIGCHLD │ pid_t si_pid │ Child process ID. │
334 │ │ int si_status │ Exit value or signal. │
335 │ │ uid_t si_uid │ Real user ID of the process that sent the signal. │
336 ├────────┼────────────────┼───────────────────────────────────────────────────┤
337 │SIGPOLL │ long si_band │ Band event for POLL_IN, POLL_OUT, or POLL_MSG. │
338 └────────┴────────────────┴───────────────────────────────────────────────────┘
339 For some implementations, the value of si_addr may be inaccurate.
340 The following shall be declared as functions and may also be defined as
342 macros. Function prototypes shall be provided.
343 int kill(pid_t, int);
345 int killpg(pid_t, int);
346 void psiginfo(const siginfo_t *, const char *);
347 void psignal(int, const char *);
348 int pthread_kill(pthread_t, int);
349 int pthread_sigmask(int, const sigset_t *restrict,
350 sigset_t *restrict);
351 int raise(int);
352 int sigaction(int, const struct sigaction *restrict,
353 struct sigaction *restrict);
354 int sigaddset(sigset_t *, int);
355 int sigaltstack(const stack_t *restrict, stack_t *restrict);
356 int sigdelset(sigset_t *, int);
357 int sigemptyset(sigset_t *);
358 int sigfillset(sigset_t *);
359 int sighold(int);
360 int sigignore(int);
361 int siginterrupt(int, int);
362 int sigismember(const sigset_t *, int);
363 void (*signal(int, void (*)(int)))(int);
364 int sigpause(int);
365 int sigpending(sigset_t *);
366 int sigprocmask(int, const sigset_t *restrict, sigset_t *restrict);
367 int sigqueue(pid_t, int, const union sigval);
368 int sigrelse(int);
369 void (*sigset(int, void (*)(int)))(int);
370 int sigsuspend(const sigset_t *);
371 int sigtimedwait(const sigset_t *restrict, siginfo_t *restrict,
372 const struct timespec *restrict);
373 int sigwait(const sigset_t *restrict, int *restrict);
374 int sigwaitinfo(const sigset_t *restrict, siginfo_t *restrict);
375 Inclusion of the <signal.h> header may make visible all symbols from
377 the <time.h> header.
378 The following sections are informative.
380
382 On systems not supporting the XSI option, the si_pid and si_uid members
383 of siginfo_t are only required to be valid when si_code is SI_USER or
384 SI_QUEUE. On XSI-conforming systems, they are also valid for all
385 si_code values less than or equal to 0; however, it is unspecified
386 whether SI_USER and SI_QUEUE have values less than or equal to zero,
387 and therefore XSI applications should check whether si_code has the
388 value SI_USER or SI_QUEUE or is less than or equal to 0 to tell whether
389 si_pid and si_uid are valid.
390
392 None.
393
395 The SIGPOLL and SIGPROF signals may be removed in a future version.
396
398 <errno.h>, <stropts.h>, <sys_types.h>, <time.h>
399 The System Interfaces volume of POSIX.1‐2008, Section 2.2, The Compila‐
401 tion Environment, alarm(), ioctl(), kill(), killpg(), psiginfo(),
402 pthread_kill(), pthread_sigmask(), raise(), sigaction(), sigaddset(),
403 sigaltstack(), sigdelset(), sigemptyset(), sigfillset(), sighold(),
404 siginterrupt(), sigismember(), signal(), sigpending(), sigqueue(), sig‐
405 suspend(), sigtimedwait(), sigwait(), timer_create(), wait(), waitid()
406
408 Portions of this text are reprinted and reproduced in electronic form
409 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
410 -- Portable Operating System Interface (POSIX), The Open Group Base
411 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
412 cal and Electronics Engineers, Inc and The Open Group. (This is
413 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
414 event of any discrepancy between this version and the original IEEE and
415 The Open Group Standard, the original IEEE and The Open Group Standard
416 is the referee document. The original Standard can be obtained online
417 at http://www.unix.org/online.html .
418 Any typographical or formatting errors that appear in this page are
420 most likely to have been introduced during the conversion of the source
421 files to man page format. To report such errors, see https://www.ker‐
422 nel.org/doc/man-pages/reporting_bugs.html .
423IEEE/The Open Group 2013 signal.h(0P)