signal(3f) [bsd man page]

SIGNAL(3F)																SIGNAL(3F)

NAME

       signal - change the action for a signal

SYNOPSIS

       integer function signal(signum, proc, flag)
       integer signum, flag
       external proc

DESCRIPTION

       When  a	process  incurs  a  signal  (see signal(3C)) the default action is usually to clean up and abort.  The user may choose to write an
       alternative signal handling routine.  A call to signal is the way this alternate action is specified to the system.

       Signum is the signal number (see signal(3C)).  If flag is negative, then proc must be the name of the user  signal  handling  routine.	If
       flag  is zero or positive, then proc is ignored and the value of flag is passed to the system as the signal action definition.  In particu-
       lar, this is how previously saved signal actions can be restored.  Two possible values for flag have specific meanings: 0  means  "use  the
       default action" (See NOTES below), 1 means "ignore this signal".

       A  positive  returned  value  is  the previous action definition.  A value greater than 1 is the address of a routine that was to have been
       called on occurrence of the given signal.  The returned value can be used in subsequent calls to signal in  order  to  restore  a  previous
       action definition.  A negative returned value is the negation of a system error code.  (See perror(3F))

FILES

       /usr/lib/libU77.a

SEE ALSO

       signal(3C), kill(3F), kill(1)

NOTES

       f77  arranges  to  trap	certain signals when a process is started.  The only way to restore the default f77 action is to save the returned
       value from the first call to signal.

       If the user signal handler is called, it will be passed the signal number as an integer argument.

4.2 Berkeley Distribution					   May 15, 1985 							SIGNAL(3F)

sigset(3C)																sigset(3C)

NAME

       sigset(), sighold(), sigrelse(), sigignore() - signal management

SYNOPSIS

DESCRIPTION

       The system defines a set of signals that can be delivered to a process.	The set of signals is defined in signal(5), along with the meaning
       and side effects of each signal.  An alternate mechanism for handling these signals is defined here.  The facilities described here  should
       not be used in conjunction with the other facilities described under signal(2) and sigspace(2).

       allows the calling process to choose one of four ways to handle the receipt of a specific signal.  sig specifies the signal and func speci-
       fies the action handler.

       sig can be any one of the signals described under signal(5) except or

       func is assigned one of four values: or a function address.  The actions prescribed by and are described under signal(5).  The action  pre-
       scribed by and function address are described below:

       Hold signal.

			 The  signal sig is held upon receipt.	Any pending signal of this signal type remains held.  Only one signal of each type
			 is held.

			 Note: the signals and cannot be held.

       function address  Catch signal.

			 func must be a pointer to a function, the signal-catching handler, that is called when signal sig occurs.  specifies that
			 the  process  calls this function upon receipt of signal sig.	Any pending signal of this type is released.  This handler
			 address is retained across calls to the other signal management functions listed here.  Upon receipt of signal  sig,  the
			 receiving  process executes the signal-catching function pointed to by func as described under signal(5) with the follow-
			 ing differences:

			 Before calling the signal-catching handler, the defined action of sig is set to During a normal return from  the  signal-
			 catching  handler,  the  defined action is restored to func and any held signal of this type is released.  If a non-local
			 goto (longjmp(3C)) is taken, must be called to restore the defined action to func and release any  held  signal  of  this
			 type.

       holds  the  signal  sig.   restores the defined action of sig to that specified previously by and are used to establish critical regions of
       code.  is analogous to raising the priority level and deferring or holding a signal until the priority is lowered by

       sets the action for signal sig to (see signal(5)).

RETURN VALUE

       Upon successful completion, returns the previous value of the defined action for the specified  signal  sig.   Otherwise,  a  value  of	is
       returned and is set to indicate the error.  is defined in

       For the other functions, a 0 value indicates that the call succeeded.  A -1 return value indicates an error occurred and is set to indicate
       the reason.

ERRORS

       fails and the defined action for sig is not changed if any of the following occur:

	      The	     func argument points to memory that is not a valid part of the process address space.   Reliable  detection  of  this
			     error is implementation dependent.

       and and fail and the defined action for sig is not changed if any of the following occur:

	      sig	     is not a valid signal number.

	      An attempt is made to ignore, hold, or supply a handler
			     for a signal that cannot be ignored, held, or caught; see signal(5).

WARNINGS

       These signal facilities should not be used in conjunction with signal(2) and sigspace(2).

SEE ALSO

       kill(1), kill(2), pause(2), signal(2), sigspace(2), wait(2), abort(3C), setjmp(3C), sigpause(3C), signal(5).

STANDARDS CONFORMANCE

																	sigset(3C)