1sigvec(3UCB) SunOS/BSD Compatibility Library Functions sigvec(3UCB)
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6 sigvec - software signal facilities
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9 /usr/ucb/cc [ flag ... ] file...
10 #include <signal.h>
11 int sigvec(sig, nvec, ovec)
13 int sig;
14 struct sigvec *nvec, *ovec;
15
18 The system defines a set of signals that may be delivered to a process.
19 Signal delivery resembles the occurrence of a hardware interrupt: the
20 signal is blocked from further occurrence, the current process context
21 is saved, and a new one is built. A process may specify a handler to
22 which a signal is delivered, or specify that a signal is to be blocked
23 or ignored. A process may also specify that a default action is to be
24 taken by the system when a signal occurs. Normally, signal handlers
25 execute on the current stack of the process. This may be changed, on a
26 per-handler basis, so that signals are taken on a special signal stack.
27 All signals have the same priority. Signal routines execute with the
30 signal that caused their invocation to be blocked, but other signals
31 may yet occur. A global signal mask defines the set of signals cur‐
32 rently blocked from delivery to a process. The signal mask for a
33 process is initialized from that of its parent (normally 0). It may be
34 changed with a sigblock() or sigsetmask() call, or when a signal is
35 delivered to the process.
36 A process may also specify a set of flags for a signal that affect the
39 delivery of that signal.
40 When a signal condition arises for a process, the signal is added to a
43 set of signals pending for the process. If the signal is not currently
44 blocked by the process then it is delivered to the process. When a
45 signal is delivered, the current state of the process is saved, a new
46 signal mask is calculated (as described below), and the signal handler
47 is invoked. The call to the handler is arranged so that if the signal
48 handling routine returns normally the process will resume execution in
49 the context from before the signal's delivery. If the process wishes
50 to resume in a different context, then it must arrange to restore the
51 previous context itself.
52 When a signal is delivered to a process a new signal mask is installed
55 for the duration of the process' signal handler (or until a sigblock()
56 or sigsetmask() call is made). This mask is formed by taking the cur‐
57 rent signal mask, adding the signal to be delivered, and ORing in the
58 signal mask associated with the handler to be invoked.
59 The action to be taken when the signal is delivered is specified by a
62 sigvec() structure, which includes the following members:
63 void (*sv_handler)(); /* signal handler */
65 int sv_mask; /* signal mask to apply */
66 int sv_flags; /* see signal options */
67 #define SV_ONSTACK /* take signal on signal stack */
68 #define SV_INTERRUPT /* do not restart system on signal
69 return */
70 #define SV_RESETHAND /* reset handler to SIG_DFL when
71 signal taken*/
72 If the SV_ONSTACK bit is set in the flags for that signal, the system
76 will deliver the signal to the process on the signal stack specified
77 with sigstack(3UCB) rather than delivering the signal on the current
78 stack.
79 If nvec is not a NULL pointer, sigvec() assigns the handler specified
82 by sv_handler(), the mask specified by sv_mask(), and the flags speci‐
83 fied by sv_flags() to the specified signal. If nvec is a NULL pointer,
84 sigvec() does not change the handler, mask, or flags for the specified
85 signal.
86 The mask specified in nvec is not allowed to block SIGKILL, SIGSTOP, or
89 SIGCONT. The system enforces this restriction silently.
90 If ovec is not a NULL pointer, the handler, mask, and flags in effect
93 for the signal before the call to sigvec() are returned to the user. A
94 call to sigvec() with nvec a NULL pointer and ovec not a NULL pointer
95 can be used to determine the handling information currently in effect
96 for a signal without changing that information.
97 The following is a list of all signals with names as in the include
100 file <signal.h>:
101 SIGHUP hangup
103 SIGINT interrupt
106 SIGQUIT* quit
109 SIGILL* illegal instruction
112 SIGTRAP* trace trap
115 SIGABRT* abort (generated by abort(3C) routine)
118 SIGEMT* emulator trap
121 SIGFPE* arithmetic exception
124 SIGKILL kill (cannot be caught, blocked, or ignored)
127 SIGBUS* bus error
130 SIGSEGV* segmentation violation
133 SIGSYS* bad argument to function
136 SIGPIPE write on a pipe or other socket with no one to read it
139 SIGALRM alarm clock
142 SIGTERM software termination signal
145 SIGURG* urgent condition present on socket
148 SIGSTOP** stop (cannot be caught, blocked, or ignored)
151 SIGTSTP** stop signal generated from keyboard
154 SIGCONT* continue after stop (cannot be blocked)
157 SIGCHLD* child status has changed
160 SIGTTIN** background read attempted from control terminal
163 SIGTTOU** background write attempted to control terminal
166 SIGIO* I/O is possible on a descriptor (see fcntl(2))
169 SIGXCPU cpu time limit exceeded (see getrlimit(2))
172 SIGXFSZ file size limit exceeded (see getrlimit(2))
175 SIGVTALRM virtual time alarm; see setitimer() on getitimer(2)
178 SIGPROF profiling timer alarm; see setitimer() on getitimer(2)
181 SIGWINCH* window changed (see termio(7I))
184 SIGLOST resource lost (see lockd(1M))
187 SIGUSR1 user-defined signal 1
190 SIGUSR2 user-defined signal 2
193 The starred signals in the list above cause a core image if not caught
197 or ignored.
198 Once a signal handler is installed, it remains installed until another
201 sigvec() call is made, or an execve(2) is performed, unless the
202 SV_RESETHAND bit is set in the flags for that signal. In that case,
203 the value of the handler for the caught signal will be set to SIG_DFL
204 before entering the signal-catching function, unless the signal is SIG‐
205 ILL, SIGPWR, or SIGTRAP. Also, if this bit is set, the bit for that
206 signal in the signal mask will not be set; unless the signal mask asso‐
207 ciated with that signal blocks that signal, further occurrences of that
208 signal will not be blocked. The SV_RESETHAND flag is not available in
209 4.2BSD, hence it should not be used if backward compatibility is
210 needed.
211 The default action for a signal may be reinstated by setting the sig‐
214 nal's handler to SIG_DFL; this default is termination except for sig‐
215 nals marked with * or **. Signals marked with * are discarded if the
216 action is SIG_DFL; signals marked with ** cause the process to stop. If
217 the process is terminated, a "core image" will be made in the current
218 working directory of the receiving process if the signal is one for
219 which an asterisk appears in the above list (see core(4)).
220 If the handler for that signal is SIG_IGN, the signal is subsequently
223 ignored, and pending instances of the signal are discarded.
224 If a caught signal occurs during certain functions, the call is nor‐
227 mally restarted. The call can be forced to terminate prematurely with
228 an EINTR error return by setting the SV_INTERRUPT bit in the flags for
229 that signal. The SV_INTERRUPT flag is not available in 4.2BSD, hence it
230 should not be used if backward compatibility is needed. The affected
231 functions are read(2) or write(2) on a slow device (such as a terminal
232 or pipe or other socket, but not a file) and during a wait(3C).
233 After a fork(2) or vfork(2) the child inherits all signals, the signal
236 mask, the signal stack, and the restart/interrupt and reset-signal-han‐
237 dler flags.
238 The execve(2) call resets all caught signals to default action and
241 resets all signals to be caught on the user stack. Ignored signals
242 remain ignored; the signal mask remains the same; signals that inter‐
243 rupt functions continue to do so.
244 The accuracy of addr is machine dependent. For example, certain
247 machines may supply an address that is on the same page as the address
248 that caused the fault. If an appropriate addr cannot be computed it
249 will be set to SIG_NOADDR.
250
252 A 0 value indicates that the call succeeded. A −1 return value indi‐
253 cates that an error occurred and errno is set to indicate the reason.
254
256 sigvec() will fail and no new signal handler will be installed if one
257 of the following occurs:
258 EFAULT Either nvec or ovec is not a NULL pointer and points to mem‐
260 ory that is not a valid part of the process address space.
261 EINVAL sig is not a valid signal number or is SIGKILL or SIGSTOP.
264
267 Intro(2), exec(2), fcntl(2), fork(2), getitimer(2), getrlimit(2),
268 ioctl(2), kill(2), read(2), umask(2), vfork(2), write(2), ptrace(3C),
269 setjmp(3C) sigblock(3UCB), signal(3C), signal(3UCB), sigstack(3UCB),
270 wait(3C), wait(3UCB), core(4), streamio(7I), termio(7I)
271
273 Use of these interfaces should be restricted to only applications writ‐
274 ten on BSD platforms. Use of these interfaces with any of the system
275 libraries or in multi-thread applications is unsupported.
276 SIGPOLL is a synonym for SIGIO. A SIGIO will be issued when a file
279 descriptor corresponding to a STREAMS (see Intro(2)) file has a
280 "selectable" event pending. Unless that descriptor has been put into
281 asynchronous mode (see fcntl(2)), a process may specifically request
282 that this signal be sent using the I_SETSIG ioctl(2) call (see
283 streamio(7I)). Otherwise, the process will never receive SIGPOLLs0.
284 The handler routine can be declared:
287 void handler(int sig, int code, struct sigcontext *scp,
289 char *addr);
290 Here sig is the signal number; code is a parameter of certain signals
294 that provides additional detail; scp is a pointer to the sigcontext
295 structure (defined in signal.h), used to restore the context from
296 before the signal; and addr is additional address information.
297 The signals SIGKILL, SIGSTOP, and SIGCONT cannot be ignored.
300SunOS 5.11 30 Oct 2007 sigvec(3UCB)