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Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" $OpenBSD: sigvec.3,v 1.28 2011/09/03 22:59:07 jmc Exp $ 29.\" 30.Dd $Mdocdate: September 3 2011 $ 31.Dt SIGVEC 3 32.Os 33.Sh NAME 34.Nm sigvec 35.Nd software signal facilities 36.Sh SYNOPSIS 37.Fd #include <signal.h> 38.Pp 39.Bd -literal 40struct sigvec { 41 void (*sv_handler)(); 42 int sv_mask; 43 int sv_flags; 44}; 45.Ed 46.Ft int 47.Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec" 48.Sh DESCRIPTION 49.Bf -symbolic 50This interface is made obsolete by 51.Xr sigaction 2 . 52.Ef 53.Pp 54The system defines a set of signals that may be delivered to a process. 55Signal delivery resembles the occurrence of a hardware interrupt: 56the signal is blocked from further occurrence, the current process 57context is saved, and a new one is built. 58A process may specify a 59.Em handler 60to which a signal is delivered, or specify that a signal is to be 61.Em blocked 62or 63.Em ignored . 64A process may also specify that a default action is to be taken 65by the system when a signal occurs. 66A signal may also be 67.Em blocked , 68in which case its delivery is postponed until it is 69.Em unblocked . 70The action to be taken on delivery is determined at the time 71of delivery. 72Normally, signal handlers execute on the current stack 73of the process. 74This may be changed, on a per-handler basis, 75so that signals are taken on a special 76.Em "signal stack" . 77.Pp 78All signals have the same 79.Em priority . 80Signal routines execute with the signal that caused their 81invocation 82.Em blocked , 83but other signals may yet occur. 84A global 85.Em "signal mask" 86defines the set of signals currently blocked from delivery 87to a process. 88The signal mask for a process is initialized 89from that of its parent (normally 0). 90It may be changed with a 91.Xr sigblock 3 92or 93.Xr sigsetmask 3 94call, or when a signal is delivered to the process. 95.Pp 96When a signal 97condition arises for a process, the signal is added to a set of 98signals pending for the process. 99If the signal is not currently 100.Em blocked 101by the process then it is delivered to the process. 102When a caught signal 103is delivered, the current state of the process is saved, 104a new signal mask is calculated (as described below), 105and the signal handler is invoked. 106The call to the handler 107is arranged so that if the signal handling routine returns 108normally the process will resume execution in the context 109from before the signal's delivery. 110If the process wishes to resume in a different context, then it 111must arrange to restore the previous context itself. 112.Pp 113When a signal is delivered to a process a new signal mask is 114installed for the duration of the process' signal handler 115(or until a 116.Xr sigblock 3 117or 118.Xr sigsetmask 3 119call is made). 120This mask is formed by taking the union of the current signal mask, 121the signal to be delivered, and 122the signal mask associated with the handler to be invoked. 123.Pp 124.Fn sigvec 125assigns a handler for a specific signal. 126If 127.Fa vec 128is non-zero, it 129specifies an action 130.Pf ( Dv SIG_DFL , 131.Dv SIG_IGN , 132or a handler routine) and mask 133to be used when delivering the specified signal. 134If 135.Fa ovec 136is non-zero, the previous handling information for the signal 137is returned to the user. 138.Pp 139Once a signal handler is installed, it remains installed 140until another 141.Fn sigvec 142call is made, or an 143.Xr execve 2 144is performed. 145A signal-specific default action may be reset by 146setting 147.Fa sv_handler 148to 149.Dv SIG_DFL . 150The defaults are process termination, possibly with core dump; 151no action; stopping the process; or continuing the process. 152See the signal list below for each signal's default action. 153If 154.Fa sv_handler 155is set to 156.Dv SIG_IGN , 157the default action for the signal is to discard the signal, 158and if a signal is pending, 159the pending signal is discarded even if the signal is masked. 160If 161.Fa sv_handler 162is set to 163.Dv SIG_IGN , 164current and pending instances 165of the signal are ignored and discarded. 166.Pp 167Options may be specified by setting 168.Em sv_flags . 169If the 170.Dv SV_ONSTACK 171bit is set in 172.Fa sv_flags , 173the system will deliver the signal to the process on a 174.Em "signal stack" , 175specified with 176.Xr sigstack 2 . 177.Pp 178If a signal is caught during the system calls listed below, 179the call may be restarted, 180the call may return with a data transfer shorter than requested, 181or the call may be forced to terminate 182with the error 183.Er EINTR . 184Interrupting of pending calls is requested 185by setting the 186.Dv SV_INTERRUPT 187bit in 188.Ar sv_flags . 189The affected system calls include 190.Xr open 2 , 191.Xr read 2 , 192.Xr write 2 , 193.Xr sendto 2 , 194.Xr recvfrom 2 , 195.Xr sendmsg 2 196and 197.Xr recvmsg 2 198on a communications channel or a slow device (such as a terminal, 199but not a regular file) 200and during a 201.Xr wait 2 202or 203.Xr ioctl 2 . 204However, calls that have already committed are not restarted, 205but instead return a partial success (for example, a short read count). 206.Pp 207After a 208.Xr fork 2 209or 210.Xr vfork 2 211all signals, the signal mask, the signal stack, 212and the interrupt/restart flags are inherited by the child. 213.Pp 214.Xr execve 2 215reinstates the default 216action for all signals which were caught and 217resets all signals to be caught on the user stack. 218Ignored signals remain ignored; 219the signal mask remains the same; 220signals that interrupt pending system calls continue to do so. 221.Pp 222The following is a list of all signals 223with names as in the include file 224.Aq Pa signal.h : 225.Bl -column "SIGVTALRM" "create core image" "terminal line hangup" 226.It Sy "Name" Ta Sy "Default Action" Ta Sy "Description" 227.It Dv SIGHUP Ta "terminate process" Ta "terminal line hangup" 228.It Dv SIGINT Ta "terminate process" Ta "interrupt program" 229.It Dv SIGQUIT Ta "create core image" Ta "quit program" 230.It Dv SIGILL Ta "create core image" Ta "illegal instruction" 231.It Dv SIGTRAP Ta "create core image" Ta "trace trap" 232.It Dv SIGABRT Ta "create core image" Ta "abort(3) call (formerly SIGIOT)" 233.It Dv SIGEMT Ta "create core image" Ta "emulate instruction executed" 234.It Dv SIGFPE Ta "create core image" Ta "floating-point exception" 235.It Dv SIGKILL Ta "terminate process" Ta "kill program (cannot be caught or ignored)" 236.It Dv SIGBUS Ta "create core image" Ta "bus error" 237.It Dv SIGSEGV Ta "create core image" Ta "segmentation violation" 238.It Dv SIGSYS Ta "create core image" Ta "system call given invalid argument" 239.It Dv SIGPIPE Ta "terminate process" Ta "write on a pipe with no reader" 240.It Dv SIGALRM Ta "terminate process" Ta "real-time timer expired" 241.It Dv SIGTERM Ta "terminate process" Ta "software termination signal" 242.It Dv SIGURG Ta "discard signal" Ta "urgent condition present on socket" 243.It Dv SIGSTOP Ta "stop process" Ta "stop (cannot be caught or ignored)" 244.It Dv SIGTSTP Ta "stop process" Ta "stop signal generated from keyboard" 245.It Dv SIGCONT Ta "discard signal" Ta "continue after stop" 246.It Dv SIGCHLD Ta "discard signal" Ta "child status has changed" 247.It Dv SIGTTIN Ta "stop process" Ta "background read attempted from control terminal" 248.It Dv SIGTTOU Ta "stop process" Ta "background write attempted to control terminal" 249.It Dv SIGIO Ta "discard signal" Ta "I/O is possible on a descriptor (see" 250.Xr fcntl 2 ) 251.It Dv SIGXCPU Ta "terminate process" Ta "CPU time limit exceeded (see" 252.Xr setrlimit 2 ) 253.It Dv SIGXFSZ Ta "terminate process" Ta "file size limit exceeded (see" 254.Xr setrlimit 2 ) 255.It Dv SIGVTALRM Ta "terminate process" Ta "virtual time alarm (see" 256.Xr setitimer 2 ) 257.It Dv SIGPROF Ta "terminate process" Ta "profiling timer alarm (see" 258.Xr setitimer 2 ) 259.It Dv SIGWINCH Ta "discard signal" Ta "window size change" 260.It Dv SIGINFO Ta "discard signal" Ta "status request from keyboard" 261.It Dv SIGUSR1 Ta "terminate process" Ta "user-defined signal 1" 262.It Dv SIGUSR2 Ta "terminate process" Ta "user-defined signal 2" 263.El 264.Sh NOTES 265The mask specified in 266.Fa vec 267is not allowed to block 268.Dv SIGKILL 269or 270.Dv SIGSTOP . 271This is enforced silently by the system. 272.Pp 273The 274.Dv SV_INTERRUPT 275flag is not available in 276.Bx 4.2 , 277hence it should not be used if backward compatibility is needed. 278.Sh RETURN VALUES 279A 0 value indicated that the call succeeded. 280A \-1 return value indicates an error occurred and 281.Va errno 282is set to indicated the reason. 283.Sh EXAMPLES 284For an example of signal handler declarations, see 285.Xr sigaction 2 . 286.Sh ERRORS 287.Fn sigvec 288will fail and no new signal handler will be installed if one 289of the following occurs: 290.Bl -tag -width Er 291.It Bq Er EFAULT 292Either 293.Fa vec 294or 295.Fa ovec 296points to memory that is not a valid part of the process 297address space. 298.It Bq Er EINVAL 299.Fa sig 300is not a valid signal number. 301.It Bq Er EINVAL 302An attempt is made to ignore or supply a handler for 303.Dv SIGKILL 304or 305.Dv SIGSTOP . 306.El 307.Sh SEE ALSO 308.Xr kill 1 , 309.Xr kill 2 , 310.Xr ptrace 2 , 311.Xr sigaction 2 , 312.Xr sigaltstack 2 , 313.Xr sigprocmask 2 , 314.Xr sigstack 2 , 315.Xr sigsuspend 2 , 316.Xr setjmp 3 , 317.Xr sigblock 3 , 318.Xr siginterrupt 3 , 319.Xr sigpause 3 , 320.Xr sigsetmask 3 , 321.Xr sigsetops 3 , 322.Xr tty 4 323