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<signal.h>(P)			    POSIX Programmer's Manual			    <signal.h>(P)

NAME
       signal.h - signals

SYNOPSIS
       #include <signal.h>

DESCRIPTION
       Some  of  the  functionality  described on this reference page extends the ISO C standard.
       Applications shall define the appropriate feature test macro (see  the  System  Interfaces
       volume  of  IEEE Std 1003.1-2001,  Section 2.2, The Compilation Environment) to enable the
       visibility of these symbols in this header.

       The <signal.h> header shall define the following symbolic constants, each of which expands
       to a distinct constant expression of the type:

	      void (*)(int)

       whose value matches no declarable function.

       SIG_DFL
	      Request for default signal handling.

       SIG_ERR
	      Return value from signal() in case of error.

       SIG_HOLD
	      Request that signal be held.

       SIG_IGN
	      Request that signal be ignored.

       The following data types shall be defined through typedef:

       sig_atomic_t
	      Possibly	volatile-qualified  integer  type of an object that can be accessed as an
	      atomic entity, even in the presence of asynchronous interrupts.

       sigset_t
	      Integer or structure type of an object used to represent sets of signals.

       pid_t  As described in <sys/types.h> .

       The <signal.h> header shall define the sigevent structure, which has at least the  follow-
       ing members:

	      int		     sigev_notify	     Notification type.
	      int		     sigev_signo	     Signal number.
	      union sigval	     sigev_value	     Signal value.
	      void(*)(union sigval)  sigev_notify_function   Notification function.
	      (pthread_attr_t *)     sigev_notify_attributes Notification attributes.

       The following values of sigev_notify shall be defined:

       SIGEV_NONE
	      No asynchronous notification is delivered when the event of interest occurs.

       SIGEV_SIGNAL
	      A  queued signal, with an application-defined value, is generated when the event of
	      interest occurs.

       SIGEV_THREAD
	      A notification function is called to perform notification.

       The sigval union shall be defined as:

	      int    sival_int	  Integer signal value.
	      void  *sival_ptr	  Pointer signal value.

       This header shall also declare the macros SIGRTMIN and SIGRTMAX, which evaluate to integer
       expressions,  and  specify a range of signal numbers that are reserved for application use
       and  for  which	 the   realtime   signal   behavior   specified   in   this   volume   of
       IEEE Std 1003.1-2001  is supported. The signal numbers in this range do not overlap any of
       the signals specified in the following table.

       The range SIGRTMIN through SIGRTMAX inclusive shall include at  least  {RTSIG_MAX}  signal
       numbers.

       It  is implementation-defined whether realtime signal behavior is supported for other sig-
       nals.

       This header also declares the constants that are used to refer to the signals  that  occur
       in  the	system. Signals defined here begin with the letters SIG. Each of the signals have
       distinct positive integer values. The value 0 is reserved for use as the null signal  (see
       kill()). Additional implementation-defined signals may occur in the system.

       The  ISO C  standard  only  requires  the  signal  names  SIGABRT, SIGFPE, SIGILL, SIGINT,
       SIGSEGV, and SIGTERM to be defined.

       The following signals shall be supported  on  all  implementations  (default  actions  are
       explained below the table):

		   Signal    Default Action Description
		   SIGABRT   A		    Process abort signal.
		   SIGALRM   T		    Alarm clock.
		   SIGBUS    A		    Access to an undefined portion of a mem-
					    ory object.
		   SIGCHLD   I		    Child process terminated, stopped,
					    or continued.
		   SIGCONT   C		    Continue executing, if stopped.
		   SIGFPE    A		    Erroneous arithmetic operation.
		   SIGHUP    T		    Hangup.
		   SIGILL    A		    Illegal instruction.
		   SIGINT    T		    Terminal interrupt signal.
		   SIGKILL   T		    Kill (cannot be caught or ignored).
		   SIGPIPE   T		    Write on a pipe with no one to read it.
		   SIGQUIT   A		    Terminal quit signal.
		   SIGSEGV   A		    Invalid memory reference.
		   SIGSTOP   S		    Stop executing (cannot be caught or
					    ignored).
		   SIGTERM   T		    Termination signal.
		   SIGTSTP   S		    Terminal stop signal.
		   SIGTTIN   S		    Background process attempting read.
		   SIGTTOU   S		    Background process attempting write.
		   SIGUSR1   T		    User-defined signal 1.
		   SIGUSR2   T		    User-defined signal 2.
		   SIGPOLL   T		    Pollable event.
		   SIGPROF   T		    Profiling timer expired.
		   SIGSYS    A		    Bad system call.
		   SIGTRAP   A		    Trace/breakpoint trap.
		   SIGURG    I		    High bandwidth data is available at a
					    socket.
		   SIGVTALRM T		    Virtual timer expired.
		   SIGXCPU   A		    CPU time limit exceeded.

		   SIGXFSZ   A		    File size limit exceeded.

       The default actions are as follows:

       T      Abnormal termination of the process. The process is terminated with all the  conse-
	      quences  of  _exit()  except that the status made available to wait() and waitpid()
	      indicates abnormal termination by the specified signal.

       A      Abnormal termination of the process.
	      Additionally, implementation-defined abnormal termination actions, such as creation
	      of a core file, may occur.

       I      Ignore the signal.

       S      Stop the process.

       C      Continue the process, if it is stopped; otherwise, ignore the signal.

       The header shall provide a declaration of struct sigaction, including at least the follow-
       ing members:

	      void (*sa_handler)(int)  Pointer to a signal-catching function or one of the macros
				       SIG_IGN or SIG_DFL.
	      sigset_t sa_mask	       Set of signals to be blocked during execution of the signal
				       handling function.
	      int      sa_flags        Special flags.
	      void (*sa_sigaction)(int, siginfo_t *, void *)
				       Pointer to a signal-catching function.

       The storage occupied by sa_handler and sa_sigaction may overlap, and a conforming applica-
       tion shall not use both simultaneously.

       The following shall be declared as constants:

       SA_NOCLDSTOP
	      Do not generate SIGCHLD when children stop
	      or stopped children continue.

       SIG_BLOCK
	      The  resulting set is the union of the current set and the signal set pointed to by
	      the argument set.

       SIG_UNBLOCK
	      The resulting set is the intersection of the current set and the complement of  the
	      signal set pointed to by the argument set.

       SIG_SETMASK
	      The resulting set is the signal set pointed to by the argument set.

       SA_ONSTACK
	      Causes signal delivery to occur on an alternate stack.

       SA_RESETHAND
	      Causes signal dispositions to be set to SIG_DFL on entry to signal handlers.

       SA_RESTART
	      Causes certain functions to become restartable.

       SA_SIGINFO
	      Causes  extra information to be passed to signal handlers at the time of receipt of
	      a signal.

       SA_NOCLDWAIT
	      Causes implementations not to create zombie processes on child death.

       SA_NODEFER
	      Causes signal not to be automatically blocked on entry to signal handler.

       SS_ONSTACK
	      Process is executing on an alternate signal stack.

       SS_DISABLE
	      Alternate signal stack is disabled.

       MINSIGSTKSZ
	      Minimum stack size for a signal handler.

       SIGSTKSZ
	      Default size in bytes for the alternate signal stack.

       The ucontext_t structure shall be defined through typedef as described in <ucontext.h>.

       The mcontext_t type shall be defined through typedef as described in <ucontext.h>.

       The <signal.h> header shall define the stack_t type as a structure that includes at  least
       the following members:

	      void     *ss_sp	    Stack base or pointer.
	      size_t	ss_size     Stack size.
	      int	ss_flags    Flags.

       The  <signal.h> header shall define the sigstack structure that includes at least the fol-
       lowing members:

	      int	ss_onstack  Non-zero when signal stack is in use.
	      void     *ss_sp	    Signal stack pointer.

       The <signal.h> header shall define the siginfo_t type as  a  structure  that  includes  at
       least the following members:

	      int	    si_signo  Signal number.

	      int	    si_errno  If non-zero, an errno value associated with
				      this signal, as defined in <errno.h>.

	      int	    si_code   Signal code.

	      pid_t	    si_pid    Sending process ID.
	      uid_t	    si_uid    Real user ID of sending process.
	      void	   *si_addr   Address of faulting instruction.
	      int	    si_status Exit value or signal.
	      long	    si_band   Band event for SIGPOLL.

	      union sigval  si_value  Signal value.

       The macros specified in the Code column of the following table are defined for use as val-
       ues of si_code that are	signal-specific or  non-signal-specific reasons  why  the  signal
       was generated.

		   Signal    Code	     Reason
		   SIGILL    ILL_ILLOPC      Illegal opcode.
			     ILL_ILLOPN      Illegal operand.
			     ILL_ILLADR      Illegal addressing mode.

			     ILL_ILLTRP      Illegal trap.
			     ILL_PRVOPC      Privileged opcode.
			     ILL_PRVREG      Privileged register.
			     ILL_COPROC      Coprocessor error.
			     ILL_BADSTK      Internal stack error.
		   SIGFPE    FPE_INTDIV      Integer divide by zero.
			     FPE_INTOVF      Integer overflow.
			     FPE_FLTDIV      Floating-point divide by zero.
			     FPE_FLTOVF      Floating-point overflow.
			     FPE_FLTUND      Floating-point underflow.
			     FPE_FLTRES      Floating-point inexact result.
			     FPE_FLTINV      Invalid floating-point operation.
			     FPE_FLTSUB      Subscript out of range.
		   SIGSEGV   SEGV_MAPERR     Address not mapped to object.
			     SEGV_ACCERR     Invalid permissions for mapped object.
		   SIGBUS    BUS_ADRALN      Invalid address alignment.
			     BUS_ADRERR      Nonexistent physical address.
			     BUS_OBJERR      Object-specific hardware error.
		   SIGTRAP   TRAP_BRKPT      Process breakpoint.
			     TRAP_TRACE      Process trace trap.
		   SIGCHLD   CLD_EXITED      Child has exited.
			     CLD_KILLED      Child has terminated abnormally and did
					     not create a core file.
			     CLD_DUMPED      Child has terminated abnormally and cre-
					     ated a core file.
			     CLD_TRAPPED     Traced child has trapped.
			     CLD_STOPPED     Child has stopped.
			     CLD_CONTINUED   Stopped child has continued.
		   SIGPOLL   POLL_IN	     Data input available.
			     POLL_OUT	     Output buffers available.
			     POLL_MSG	     Input message available.
			     POLL_ERR	     I/O error.
			     POLL_PRI	     High priority input available.
			     POLL_HUP	     Device disconnected.
		   Any	     SI_USER	     Signal sent by kill().
			     SI_QUEUE	     Signal sent by the sigqueue().
			     SI_TIMER	     Signal generated by expiration of a
					     timer set by timer_settime().
			     SI_ASYNCIO      Signal generated by completion of an
					     asynchronous I/O request.
			     SI_MESGQ	     Signal generated by arrival of a message
					     on an empty message queue.

       Implementations may support additional si_code values not included in this list, may  gen-
       erate  values included in this list under circumstances other than those described in this
       list, and may contain extensions or limitations that prevent some values from being gener-
       ated.  Implementations  do  not generate a different value from the ones described in this
       list for circumstances described in this list.

       In addition, the following signal-specific information shall be available:

		Signal	Member	       Value
		SIGILL	void * si_addr Address of faulting instruction.
		SIGFPE
		SIGSEGV void * si_addr Address of faulting memory reference.
		SIGBUS
		SIGCHLD pid_t si_pid   Child process ID.
			int si_status  Exit value or signal.
			uid_t si_uid   Real user ID of the process that sent the signal.
		SIGPOLL long si_band   Band event for POLL_IN, POLL_OUT, or POLL_MSG.

       For some implementations, the value of si_addr may be inaccurate.

       The following shall be declared as functions and may also be defined as macros:

	      void (*bsd_signal(int, void (*)(int)))(int);

	      int    kill(pid_t, int);

	      int    killpg(pid_t, int);

	      int    pthread_kill(pthread_t, int);
	      int    pthread_sigmask(int, const sigset_t *, sigset_t *);

	      int    raise(int);

	      int    sigaction(int, const struct sigaction *restrict,
			 struct sigaction *restrict);
	      int    sigaddset(sigset_t *, int);

	      int    sigaltstack(const stack_t *restrict, stack_t *restrict);

	      int    sigdelset(sigset_t *, int);
	      int    sigemptyset(sigset_t *);
	      int    sigfillset(sigset_t *);

	      int    sighold(int);
	      int    sigignore(int);
	      int    siginterrupt(int, int);

	      int    sigismember(const sigset_t *, int);

	      void (*signal(int, void (*)(int)))(int);

	      int    sigpause(int);

	      int    sigpending(sigset_t *);
	      int    sigprocmask(int, const sigset_t *restrict, sigset_t *restrict);

	      int    sigqueue(pid_t, int, const union sigval);

	      int    sigrelse(int);
	      void (*sigset(int, void (*)(int)))(int);

	      int    sigsuspend(const sigset_t *);

	      int    sigtimedwait(const sigset_t *restrict, siginfo_t *restrict,
			 const struct timespec *restrict);

	      int    sigwait(const sigset_t *restrict, int *restrict);

	      int    sigwaitinfo(const sigset_t *restrict, siginfo_t *restrict);

       Inclusion of the <signal.h> header may make visible all symbols from the <time.h> header.

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <errno.h> , <stropts.h> , <sys/types.h> , <time.h> , <ucontext.h> , the System  Interfaces
       volume of IEEE Std 1003.1-2001, alarm(), bsd_signal(), ioctl(), kill(), killpg(), raise(),
       sigaction(), sigaddset(), sigaltstack(), sigdelset(), sigemptyset(), sigfillset(),  sigin-
       terrupt(), sigismember(), signal(), sigpending(), sigprocmask(), sigqueue(), sigsuspend(),
       sigwaitinfo(), wait(), waitid()

COPYRIGHT
       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				    <signal.h>(P)
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