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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sigvec.2 8.2 (Berkeley) 4/19/94 33.\" 34.Dd April 19, 1994 35.Dt SIGVEC 2 36.Os BSD 4 37.Sh NAME 38.Nm sigvec 39.Nd software signal facilities 40.Sh SYNOPSIS 41.Fd #include <signal.h> 42.Bd -literal 43struct sigvec { 44 void (*sv_handler)(); 45 sigset_t sv_mask; 46 int sv_flags; 47}; 48.Ed 49.Ft int 50.Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec" 51.Sh DESCRIPTION 52.Bf -symbolic 53This interface is made obsolete by sigaction(2). 54.Ef 55.Pp 56The system defines a set of signals that may be delivered to a process. 57Signal delivery resembles the occurrence of a hardware interrupt: 58the signal is blocked from further occurrence, the current process 59context is saved, and a new one is built. A process may specify a 60.Em handler 61to which a signal is delivered, or specify that a signal is to be 62.Em blocked 63or 64.Em ignored . 65A process may also specify that a default action is to be taken 66by the system when a signal occurs. 67Normally, signal handlers execute on the current stack 68of the process. This may be changed, on a per-handler basis, 69so that signals are taken on a special 70.Em "signal stack" . 71.Pp 72All signals have the same 73.Em priority . 74Signal routines execute with the signal that caused their 75invocation 76.Em blocked , 77but other signals may yet occur. 78A global 79.Em "signal mask" 80defines the set of signals currently blocked from delivery 81to a process. The signal mask for a process is initialized 82from that of its parent (normally 0). It 83may be changed with a 84.Xr sigblock 2 85or 86.Xr sigsetmask 2 87call, or when a signal is delivered to the process. 88.Pp 89When a signal 90condition arises for a process, the signal is added to a set of 91signals pending for the process. If the signal is not currently 92.Em blocked 93by the process then it is delivered to the process. When a signal 94is delivered, the current state of the process is saved, 95a new signal mask is calculated (as described below), 96and the signal handler is invoked. The call to the handler 97is arranged so that if the signal handling routine returns 98normally the process will resume execution in the context 99from before the signal's delivery. 100If the process wishes to resume in a different context, then it 101must arrange to restore the previous context itself. 102.Pp 103When a signal is delivered to a process a new signal mask is 104installed for the duration of the process' signal handler 105(or until a 106.Xr sigblock 2 107or 108.Xr sigsetmask 2 109call is made). 110This mask is formed by taking the current signal mask, 111adding the signal to be delivered, and 112.Em or Ns 'ing 113in the signal mask associated with the handler to be invoked. 114.Pp 115.Fn Sigvec 116assigns a handler for a specific signal. If 117.Fa vec 118is non-zero, it 119specifies a handler routine and mask 120to be used when delivering the specified signal. 121Further, if the 122.Dv SV_ONSTACK 123bit is set in 124.Fa sv_flags , 125the system will deliver the signal to the process on a 126.Em "signal stack" , 127specified with 128.Xr sigaltstack 2 . 129If 130.Fa ovec 131is non-zero, the previous handling information for the signal 132is returned to the user. 133.Pp 134The following is a list of all signals 135with names as in the include file 136.Aq Pa signal.h : 137.Bl -column SIGVTALARMXX "create core imagexxx" 138.It Sy " NAME " " Default Action " " Description" 139.It Dv SIGHUP No " terminate process" " terminal line hangup" 140.It Dv SIGINT No " terminate process" " interrupt program" 141.It Dv SIGQUIT No " create core image" " quit program" 142.It Dv SIGILL No " create core image" " illegal instruction" 143.It Dv SIGTRAP No " create core image" " trace trap" 144.It Dv SIGABRT No " create core image" Xr abort 3 145call (formerly 146.Dv SIGIOT ) 147.It Dv SIGEMT No " create core image" " emulate instruction executed" 148.It Dv SIGFPE No " create core image" " floating-point exception" 149.It Dv SIGKILL No " terminate process" " kill program" 150.It Dv SIGBUS No " create core image" " bus error" 151.It Dv SIGSEGV No " create core image" " segmentation violation" 152.It Dv SIGSYS No " create core image" " non-existent system call invoked" 153.It Dv SIGPIPE No " terminate process" " write on a pipe with no reader" 154.It Dv SIGALRM No " terminate process" " real-time timer expired" 155.It Dv SIGTERM No " terminate process" " software termination signal" 156.It Dv SIGURG No " discard signal" " urgent condition present on socket" 157.It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)" 158.It Dv SIGTSTP No " stop process" " stop signal generated from keyboard" 159.It Dv SIGCONT No " discard signal" " continue after stop" 160.It Dv SIGCHLD No " discard signal" " child status has changed" 161.It Dv SIGTTIN No " stop process" " background read attempted from control terminal" 162.It Dv SIGTTOU No " stop process" " background write attempted to control terminal" 163.It Dv SIGIO No " discard signal" Tn " I/O" 164is possible on a descriptor (see 165.Xr fcntl 2 ) 166.It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see" 167.Xr setrlimit 2 ) 168.It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see" 169.Xr setrlimit 2 ) 170.It Dv SIGVTALRM No " terminate process" " virtual time alarm (see" 171.Xr setitimer 2 ) 172.It Dv SIGPROF No " terminate process" " profiling timer alarm (see" 173.Xr setitimer 2 ) 174.It Dv SIGWINCH No " discard signal" " Window size change" 175.It Dv SIGINFO No " discard signal" " status request from keyboard" 176.It Dv SIGUSR1 No " terminate process" " User defined signal 1" 177.It Dv SIGUSR2 No " terminate process" " User defined signal 2" 178.El 179.Pp 180Once a signal handler is installed, it remains installed 181until another 182.Fn sigvec 183call is made, or an 184.Xr execve 2 185is performed. 186A signal-specific default action may be reset by 187setting 188.Fa sv_handler 189to 190.Dv SIG_DFL . 191The defaults are process termination, possibly with core dump; 192no action; stopping the process; or continuing the process. 193See the above signal list for each signal's default action. 194If 195.Fa sv_handler 196is 197.Dv SIG_IGN 198current and pending instances 199of the signal are ignored and discarded. 200.Pp 201If a signal is caught during the system calls listed below, 202the call is normally restarted. 203The call can be forced to terminate prematurely with an 204.Dv EINTR 205error return by setting the 206.Dv SV_INTERRUPT 207bit in 208.Fa sv_flags . 209The affected system calls include 210.Xr read 2 , 211.Xr write 2 , 212.Xr sendto 2 , 213.Xr recvfrom 2 , 214.Xr sendmsg 2 215and 216.Xr recvmsg 2 217on a communications channel or a slow device (such as a terminal, 218but not a regular file) 219and during a 220.Xr wait 2 221or 222.Xr ioctl 2 . 223However, calls that have already committed are not restarted, 224but instead return a partial success (for example, a short read count). 225.Pp 226After a 227.Xr fork 2 228or 229.Xr vfork 2 230all signals, the signal mask, the signal stack, 231and the restart/interrupt flags are inherited by the child. 232.Pp 233.Xr Execve 2 234reinstates the default 235action for all signals which were caught and 236resets all signals to be caught on the user stack. 237Ignored signals remain ignored; 238the signal mask remains the same; 239signals that interrupt system calls continue to do so. 240.Sh NOTES 241The mask specified in 242.Fa vec 243is not allowed to block 244.Dv SIGKILL 245or 246.Dv SIGSTOP . 247This is done silently by the system. 248.Pp 249The 250.Dv SV_INTERRUPT 251flag is not available in 252.Bx 4.2 , 253hence it should not be used if backward compatibility is needed. 254.Sh RETURN VALUES 255A 0 value indicated that the call succeeded. A \-1 return value 256indicates an error occurred and 257.Va errno 258is set to indicated the reason. 259.Sh ERRORS 260.Fn Sigvec 261will fail and no new signal handler will be installed if one 262of the following occurs: 263.Bl -tag -width [EINVAL] 264.It Bq Er EFAULT 265Either 266.Fa vec 267or 268.Fa ovec 269points to memory that is not a valid part of the process 270address space. 271.It Bq Er EINVAL 272.Fa Sig 273is not a valid signal number. 274.It Bq Er EINVAL 275An attempt is made to ignore or supply a handler for 276.Dv SIGKILL 277or 278.Dv SIGSTOP . 279.El 280.Sh SEE ALSO 281.Xr kill 1 , 282.Xr kill 2 , 283.Xr ptrace 2 , 284.Xr sigaction 2 , 285.Xr sigaltstack 2 , 286.Xr sigblock 2 , 287.Xr sigpause 2 , 288.Xr sigprocmask 2 , 289.Xr sigsetmask 2 , 290.Xr sigsuspend 2 , 291.Xr setjmp 3 , 292.Xr siginterrupt 3 , 293.Xr signal 3 , 294.Xr sigsetops 3 , 295.Xr tty 4 296.Sh EXAMPLE 297On the 298.Tn VAX\-11 299The handler routine can be declared: 300.Bd -literal -offset indent 301void handler(sig, code, scp) 302int sig, code; 303struct sigcontext *scp; 304.Ed 305.Pp 306Here 307.Fa sig 308is the signal number, into which the hardware faults and traps are 309mapped as defined below. 310.Fa Code 311is a parameter that is either a constant 312as given below or, for compatibility mode faults, the code provided by 313the hardware (Compatibility mode faults are distinguished from the 314other 315.Dv SIGILL 316traps by having 317.Dv PSL_CM 318set in the psl). 319.Fa Scp 320is a pointer to the 321.Fa sigcontext 322structure (defined in 323.Aq Pa signal.h ) , 324used to restore the context from before the signal. 325.Sh BUGS 326This manual page is still confusing. 327