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Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" from: @(#)sigvec.2 6.7 (Berkeley) 4/29/91 .\" $Id: sigvec.3,v 1.4 1994/01/11 00:13:27 jtc Exp $ .\" .Dd April 29, 1991 .Dt SIGVEC 2 .Os BSD 4 .Sh NAME .Nm sigvec .Nd software signal facilities .Sh SYNOPSIS .Fd #include .Bd -literal struct sigvec { void (*sv_handler)(); sigset_t sv_mask; int sv_flags; }; .Ed .Fn sigvec "int sig" "struct sigvec *vec" "struct sigvec *ovec" .Sh DESCRIPTION .Bf -symbolic This interface is made obsolete by sigaction(2). .Ef .Pp The system defines a set of signals that may be delivered to a process. Signal delivery resembles the occurrence of a hardware interrupt: the signal is blocked from further occurrence, the current process context is saved, and a new one is built. A process may specify a .Em handler to which a signal is delivered, or specify that a signal is to be .Em blocked or .Em ignored . A process may also specify that a default action is to be taken by the system when a signal occurs. Normally, signal handlers execute on the current stack of the process. This may be changed, on a per-handler basis, so that signals are taken on a special .Em "signal stack" . .Pp All signals have the same .Em priority . Signal routines execute with the signal that caused their invocation .Em blocked , but other signals may yet occur. A global .Em "signal mask" defines the set of signals currently blocked from delivery to a process. The signal mask for a process is initialized from that of its parent (normally 0). It may be changed with a .Xr sigblock 2 or .Xr sigsetmask 2 call, or when a signal is delivered to the process. .Pp When a signal condition arises for a process, the signal is added to a set of signals pending for the process. If the signal is not currently .Em blocked by the process then it is delivered to the process. When a signal is delivered, the current state of the process is saved, a new signal mask is calculated (as described below), and the signal handler is invoked. The call to the handler is arranged so that if the signal handling routine returns normally the process will resume execution in the context from before the signal's delivery. If the process wishes to resume in a different context, then it must arrange to restore the previous context itself. .Pp When a signal is delivered to a process a new signal mask is installed for the duration of the process' signal handler (or until a .Xr sigblock or .Xr sigsetmask call is made). This mask is formed by taking the current signal mask, adding the signal to be delivered, and .Em or Ns 'ing in the signal mask associated with the handler to be invoked. .Pp .Fn Sigvec assigns a handler for a specific signal. If .Fa vec is non-zero, it specifies a handler routine and mask to be used when delivering the specified signal. Further, if the .Dv SV_ONSTACK bit is set in .Fa sv_flags , the system will deliver the signal to the process on a .Em "signal stack" , specified with .Xr sigstack 2 . If .Fa ovec is non-zero, the previous handling information for the signal is returned to the user. .Pp The following is a list of all signals with names as in the include file .Aq Pa signal.h : .Bl -column SIGVTALARMXX "create core imagexxx" .It Sy " NAME " " Default Action " " Description" .It Dv SIGHUP No " terminate process" " terminal line hangup" .It Dv SIGINT No " terminate process" " interrupt program" .It Dv SIGQUIT No " create core image" " quit program" .It Dv SIGILL No " create core image" " illegal instruction" .It Dv SIGTRAP No " create core image" " trace trap" .It Dv SIGABRT No " create core image" Xr abort 2 call (formerly .Dv SIGIOT ) .It Dv SIGEMT No " create core image" " emulate instruction executed" .It Dv SIGFPE No " create core image" " floating-point exception" .It Dv SIGKILL No " terminate process" " kill program" .It Dv SIGBUS No " create core image" " bus error" .It Dv SIGSEGV No " create core image" " segmentation violation" .It Dv SIGSYS No " create core image" " system call given invalid argument" .It Dv SIGPIPE No " terminate process" " write on a pipe with no reader" .It Dv SIGALRM No " terminate process" " real-time timer expired" .It Dv SIGTERM No " terminate process" " software termination signal" .It Dv SIGURG No " discard signal" " urgent condition present on socket" .It Dv SIGSTOP No " stop process" " stop (cannot be caught or ignored)" .It Dv SIGTSTP No " stop process" " stop signal generated from keyboard" .It Dv SIGCONT No " discard signal" " continue after stop" .It Dv SIGCHLD No " discard signal" " child status has changed" .It Dv SIGTTIN No " stop process" " background read attempted from control terminal" .It Dv SIGTTOU No " stop process" " background write attempted to control terminal" .It Dv SIGIO No " discard signal" Tn " I/O" is possible on a descriptor (see .Xr fcntl 2 ) .It Dv SIGXCPU No " terminate process" " cpu time limit exceeded (see" .Xr setrlimit 2 ) .It Dv SIGXFSZ No " terminate process" " file size limit exceeded (see" .Xr setrlimit 2 ) .It Dv SIGVTALRM No " terminate process" " virtual time alarm (see" .Xr setitimer 2 ) .It Dv SIGPROF No " terminate process" " profiling timer alarm (see" .Xr setitimer 2 ) .It Dv SIGWINCH No " discard signal" " Window size change" .It Dv SIGINFO No " discard signal" " status request from keyboard" .It Dv SIGUSR1 No " terminate process" " User defined signal 1" .It Dv SIGUSR2 No " terminate process" " User defined signal 2" .El .Pp Once a signal handler is installed, it remains installed until another .Fn sigvec call is made, or an .Xr execve 2 is performed. A signal-specific default action may be reset by setting .Fa sv_handler to .Dv SIG_DFL . The defaults are process termination, possibly with core dump; no action; stopping the process; or continuing the process. See the above signal list for each signal's default action. If .Fa sv_handler is .Dv SIG_IGN current and pending instances of the signal are ignored and discarded. .Pp If a signal is caught during the system calls listed below, the call is normally restarted. The call can be forced to terminate prematurely with an .Dv EINTR error return by setting the .Dv SV_INTERRUPT bit in .Fa sv_flags . The affected system calls include .Xr read 2 , .Xr write 2 , .Xr sendto 2 , .Xr recvfrom 2 , .Xr sendmsg 2 and .Xr recvmsg 2 on a communications channel or a slow device (such as a terminal, but not a regular file) and during a .Xr wait 2 or .Xr ioctl 2 . However, calls that have already committed are not restarted, but instead return a partial success (for example, a short read count). .Pp After a .Xr fork 2 or .Xr vfork 2 all signals, the signal mask, the signal stack, and the restart/interrupt flags are inherited by the child. .Pp .Xr Execve 2 reinstates the default action for all signals which were caught and resets all signals to be caught on the user stack. Ignored signals remain ignored; the signal mask remains the same; signals that interrupt system calls continue to do so. .Sh NOTES The mask specified in .Fa vec is not allowed to block .Dv SIGKILL or .Dv SIGSTOP . This is done silently by the system. .Pp The .Dv SV_INTERRUPT flag is not available in .Bx 4.2 , hence it should not be used if backward compatibility is needed. .Sh RETURN VALUES A 0 value indicated that the call succeeded. A \-1 return value indicates an error occurred and .Va errno is set to indicated the reason. .Sh ERRORS .Fn Sigvec will fail and no new signal handler will be installed if one of the following occurs: .Bl -tag -width Er .It Bq Er EFAULT Either .Fa vec or .Fa ovec points to memory that is not a valid part of the process address space. .It Bq Er EINVAL .Fa Sig is not a valid signal number. .It Bq Er EINVAL An attempt is made to ignore or supply a handler for .Dv SIGKILL or .Dv SIGSTOP . .El .Sh SEE ALSO .Xr sigaction 2 , .Xr kill 1 , .Xr ptrace 2 , .Xr kill 2 , .Xr sigprocmask 2 , .Xr sigsuspend 2 , .Xr sigblock 2 , .Xr sigsetmask 2 , .Xr sigpause 2 , .Xr sigstack 2 , .Xr sigvec 2 , .Xr sigsetops 3 , .Xr setjmp 3 , .Xr siginterrupt 3 , .Xr tty 4 .Sh EXAMPLE On the .Tn VAX\-11 The handler routine can be declared: .Bd -literal -offset indent void handler(sig, code, scp) int sig, code; struct sigcontext *scp; .Ed .Pp Here .Fa sig is the signal number, into which the hardware faults and traps are mapped as defined below. .Fa Code is a parameter that is either a constant as given below or, for compatibility mode faults, the code provided by the hardware (Compatibility mode faults are distinguished from the other .Dv SIGILL traps by having .Dv PSL_CM set in the psl). .Fa Scp is a pointer to the .Fa sigcontext structure (defined in .Aq Pa signal.h ) , used to restore the context from before the signal. .Sh BUGS This manual page is still confusing.