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NAME    [Toc]    [Back]

     sigvec - software signal facilities

SYNOPSIS    [Toc]    [Back]

     #include <signal.h>

     struct sigvec {
             void     (*sv_handler)();
             int      sv_mask;
             int      sv_flags;

     sigvec(int sig, struct sigvec *vec, struct sigvec *ovec);

DESCRIPTION    [Toc]    [Back]

     This interface is made obsolete by sigaction(2).

     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
handler to which
     a signal is delivered, or specify that a  signal  is  to  be
blocked or
     ignored.   A  process may also specify that a default action
is to be taken
     by the system when a signal occurs.  A signal  may  also  be
blocked, in
     which  case its delivery is postponed until it is unblocked.
The action
     to be taken on delivery is determined at the time of  delivery.  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
     signal stack.

     All signals have the same priority.  Signal routines execute
with the
     signal that caused their invocation blocked, but other  signals may yet
     occur.  A global 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
     sigblock(3) or sigsetmask(3) call, or when a signal  is  delivered to the

     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
     blocked  by the process then it is delivered to the process.
When a
     caught 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.

     When a signal is delivered to a process a new signal mask is
     for  the duration of the process' signal handler (or until a
     or sigsetmask(3) call is made).  This mask is formed by taking the union
     of  the current signal mask, the signal to be delivered, and
the signal
     mask associated with the handler to be invoked.

     sigvec() assigns a handler for a specific signal.  If vec is
non-zero, it
     specifies an action (SIG_DFL, SIG_IGN, or a handler routine)
and mask to
     be used when delivering the specified signal.   If  ovec  is
non-zero, the
     previous  handling information for the signal is returned to
the user.

     Once a signal handler is installed, it remains installed until another
     sigvec() call is made, or an execve(2) is performed.  A signal-specific
     default  action  may  be  reset  by  setting  sv_handler  to
SIG_DFL.  The defaults
  are process termination, possibly with core dump; no
action; stopping
 the process; or continuing the process.  See the signal
list below
     for  each  signal's default action.  If sv_handler is set to
SIG_IGN, the
     default action for the signal is to discard the signal,  and
if a signal
     is pending, the pending signal is discarded even if the signal is masked.
     If sv_handler is set to SIG_IGN,  current  and  pending  instances of the
     signal are ignored and discarded.

     Options may be specified by setting sv_flags.  If the SV_ONSTACK bit is
     set in sv_flags, the system will deliver the signal  to  the
process on a
     signal stack, specified with sigstack(2).

     If  a signal is caught during the system calls listed below,
the call may
     be restarted, the call  may  return  with  a  data  transfer
shorter than requested,
 or the call may be forced to terminate with the error EINTR.
     Interrupting of pending calls is requested  by  setting  the
     bit in sv_flags.  The affected system calls include open(2),
     write(2), sendto(2), recvfrom(2), sendmsg(2) and  recvmsg(2)
on a communications
  channel  or  a slow device (such as a terminal, but
not a regular
     file) and during a wait(2) or ioctl(2).  However, calls that
have already
     committed  are  not  restarted, but instead return a partial
success (for
     example, a short read count).

     After a fork(2) or vfork(2) all signals,  the  signal  mask,
the signal
     stack,  and the interrupt/restart flags are inherited by the

     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
     pending system calls continue to do so.

     The  following is a list of all signals with names as in the
include file

     NAME            Default Action          Description
     SIGHUP          terminate process       terminal line hangup
     SIGINT          terminate process       interrupt program
     SIGQUIT         create core image       quit program
     SIGILL          create core image       illegal instruction
     SIGTRAP         create core image       trace trap
     SIGABRT          create core image       abort(3) call (formerly SIGIOT)
     SIGEMT          create core image       emulate  instruction
     SIGFPE           create  core image       floating-point exception
     SIGKILL         terminate process       kill program (cannot
be caught or
     SIGBUS          create core image       bus error
     SIGSEGV          create core image       segmentation violation
     SIGSYS          create core image        system  call  given
     SIGPIPE         terminate process       write on a pipe with
no reader
     SIGALRM         terminate process       real-time timer  expired
     SIGTERM         terminate process       software termination
     SIGURG           discard  signal           urgent  condition
present on
     SIGSTOP          stop  process             stop  (cannot  be
caught or
     SIGTSTP         stop process            stop signal generated from
     SIGCONT         discard signal          continue after stop
     SIGCHLD          discard  signal           child  status has
     SIGTTIN         stop process            background read  attempted from
                                             control terminal
     SIGTTOU         stop process            background write attempted to
                                             control terminal
     SIGIO           discard signal          I/O is possible on a
                                             (see fcntl(2))
     SIGXCPU          terminate  process       CPU time limit exceeded (see
     SIGXFSZ         terminate process       file size limit  exceeded (see
     SIGVTALRM        terminate  process       virtual time alarm
     SIGPROF          terminate  process        profiling   timer
alarm (see
     SIGWINCH        discard signal          window size change
     SIGINFO          discard signal          status request from
     SIGUSR1         terminate process       user-defined  signal
     SIGUSR2          terminate process       user-defined signal

NOTES    [Toc]    [Back]

     The mask specified in vec is not allowed to block SIGKILL or
     This is enforced silently by the system.

     The  SV_INTERRUPT  flag is not available in 4.2BSD, hence it
should not be
     used if backward compatibility is needed.

RETURN VALUES    [Toc]    [Back]

     A 0 value indicated that the call succeeded.   A  -1  return
value indicates
     an  error occurred and errno is set to indicated the reason.

EXAMPLES    [Toc]    [Back]

     For an example of signal handler  declarations,  see  sigaction(2).

ERRORS    [Toc]    [Back]

     sigvec()  will  fail  and  no new signal handler will be installed if one of
     the following occurs:

     [EFAULT]      Either vec or ovec points to  memory  that  is
not a valid
                   part of the process address space.

     [EINVAL]      sig is not a valid signal number.

     [EINVAL]       An attempt is made to ignore or supply a handler for
                   SIGKILL or SIGSTOP.

SEE ALSO    [Toc]    [Back]

     kill(1), kill(2), ptrace(2), sigaction(2), sigaltstack(2),
     sigprocmask(2), sigstack(2), sigsuspend(2), setjmp(3),  sigblock(3),
     siginterrupt(3),  sigpause(3),  sigsetmask(3), sigsetops(3),

OpenBSD     3.6                          April      29,      1991
[ Back ]
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