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32 .\" @(#)sigvec.2 8.2 (Berkeley) 4/19/94
33 .\" $FreeBSD: src/lib/libc/compat-43/sigvec.2,v 1.9.2.8 2003/03/15 15:11:05 trhodes Exp $
34 .\" $DragonFly: src/lib/libcr/compat-43/Attic/sigvec.2,v 1.2 2003/06/17 04:26:41 dillon Exp $
41 .Nd software signal facilities
54 .Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec"
57 This interface is made obsolete by
61 The system defines a set of signals that may be delivered to a process.
62 Signal delivery resembles the occurrence of a hardware interrupt:
63 the signal is blocked from further occurrence, the current process
64 context is saved, and a new one is built. A process may specify a
66 to which a signal is delivered, or specify that a signal is to be
70 A process may also specify that a default action is to be taken
71 by the system when a signal occurs.
72 Normally, signal handlers execute on the current stack
73 of the process. This may be changed, on a per-handler basis,
74 so that signals are taken on a special
77 All signals have the same
79 Signal routines execute with the signal that caused their
82 but other signals may yet occur.
85 defines the set of signals currently blocked from delivery
86 to a process. The signal mask for a process is initialized
87 from that of its parent (normally 0). It
92 call, or when a signal is delivered to the process.
95 condition arises for a process, the signal is added to a set of
96 signals pending for the process. If the signal is not currently
98 by the process then it is delivered to the process. When a signal
99 is delivered, the current state of the process is saved,
100 a new signal mask is calculated (as described below),
101 and the signal handler is invoked. The call to the handler
102 is arranged so that if the signal handling routine returns
103 normally the process will resume execution in the context
104 from before the signal's delivery.
105 If the process wishes to resume in a different context, then it
106 must arrange to restore the previous context itself.
108 When a signal is delivered to a process a new signal mask is
109 installed for the duration of the process' signal handler
115 This mask is formed by taking the current signal mask,
116 adding the signal to be delivered, and
118 in the signal mask associated with the handler to be invoked.
123 assigns a handler for a specific signal. If
126 specifies a handler routine and mask
127 to be used when delivering the specified signal.
132 the system will deliver the signal to the process on a
138 is non-zero, the previous handling information for the signal
139 is returned to the user.
141 The following is a list of all signals
142 with names as in the include file
144 .Bl -column SIGVTALARMXX "create core imagexxx"
145 .It Sy "NAME Default Action Description"
146 .It Dv SIGHUP No " terminate process" " terminal line hangup"
147 .It Dv SIGINT No " terminate process" " interrupt program"
148 .It Dv SIGQUIT No " create core image" " quit program"
149 .It Dv SIGILL No " create core image" " illegal instruction"
150 .It Dv SIGTRAP No " create core image" " trace trap"
151 .It Dv SIGABRT No " create core image" Ta Xr abort 3
154 .It Dv SIGEMT No " create core image" " emulate instruction executed"
155 .It Dv SIGFPE No " create core image" " floating-point exception"
156 .It Dv SIGKILL No " terminate process" " kill program"
157 .It Dv SIGBUS No " create core image" " bus error"
158 .It Dv SIGSEGV No " create core image" " segmentation violation"
159 .It Dv SIGSYS No " create core image" " non-existent system call invoked"
160 .It Dv SIGPIPE No " terminate process" " write on a pipe with no reader"
161 .It Dv SIGALRM No " terminate process" " real-time timer expired"
162 .It Dv SIGTERM No " terminate process" " software termination signal"
163 .It Dv SIGURG No " discard signal" " urgent condition present on socket"
164 .It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)"
165 .It Dv SIGTSTP No " stop process" " stop signal generated from keyboard"
166 .It Dv SIGCONT No " discard signal" " continue after stop"
167 .It Dv SIGCHLD No " discard signal" " child status has changed"
168 .It Dv SIGTTIN No " stop process" " background read attempted from control terminal"
169 .It Dv SIGTTOU No " stop process" " background write attempted to control terminal"
170 .It Dv SIGIO No " discard signal" Tn " I/O"
171 is possible on a descriptor (see
173 .It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see"
175 .It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see"
177 .It Dv SIGVTALRM No " terminate process" " virtual time alarm (see"
179 .It Dv SIGPROF No " terminate process" " profiling timer alarm (see"
181 .It Dv SIGWINCH No " discard signal" " Window size change"
182 .It Dv SIGINFO No " discard signal" " status request from keyboard"
183 .It Dv SIGUSR1 No " terminate process" " User defined signal 1"
184 .It Dv SIGUSR2 No " terminate process" " User defined signal 2"
187 Once a signal handler is installed, it remains installed
193 A signal-specific default action may be reset by
198 The defaults are process termination, possibly with core dump;
199 no action; stopping the process; or continuing the process.
200 See the above signal list for each signal's default action.
205 current and pending instances
206 of the signal are ignored and discarded.
208 If a signal is caught during the system calls listed below,
209 the call is normally restarted.
210 The call can be forced to terminate prematurely with an
212 error return by setting the
216 The affected system calls include
224 on a communications channel or a slow device (such as a terminal,
225 but not a regular file)
230 However, calls that have already committed are not restarted,
231 but instead return a partial success (for example, a short read count).
237 all signals, the signal mask, the signal stack,
238 and the restart/interrupt flags are inherited by the child.
242 system call reinstates the default
243 action for all signals which were caught and
244 resets all signals to be caught on the user stack.
245 Ignored signals remain ignored;
246 the signal mask remains the same;
247 signals that interrupt system calls continue to do so.
249 The mask specified in
251 is not allowed to block
255 This is done silently by the system.
259 flag is not available in
261 hence it should not be used if backward compatibility is needed.
268 will fail and no new signal handler will be installed if one
269 of the following occurs:
276 points to memory that is not a valid part of the process
282 is not a valid signal number.
284 An attempt is made to ignore or supply a handler for
308 The handler routine can be declared:
309 .Bd -literal -offset indent
310 void handler(sig, code, scp)
312 struct sigcontext *scp;
317 is the signal number, into which the hardware faults and traps are
318 mapped as defined below.
323 as given below or, for compatibility mode faults, the code provided by
324 the hardware (Compatibility mode faults are distinguished from the
335 structure (defined in
337 used to restore the context from before the signal.
339 This manual page is still confusing.