SIGNAL(II)                   8/5/73                    SIGNAL(II)


     signal - catch or ignore signals


     (signal = 48.)

     sys  signal; sig; value

     signal(sig, func)

     int (*func)();


     When the signal defined  by  sig  is  sent  to  the  current

     process,  it  is  to  be  treated  according  to value.  The

     following is the list of signals:

          1     hangup

          2     interrupt

          3*    quit

          4*    illegal instruction

          5*    trace trap

          6*    IOT instruction

          7*    EMT instruction

          8*    floating point exception

          9     kill (cannot be caught or ignored)

          10*   bus error

          11*   segmentation violation

          12*   bad argument to sys call

     If value is 0, the default  system  action  applies  to  the

     signal.   This  is  processes  termination with or without a

     core dump.  If value is odd, the  signal  is  ignored.   Any

     other  even  value specifies an address in the process where

     an interrupt is simulated.  An RTI instruction  will  return

     from  the  interrupt.  As a signal is caught, it is reset to

     0.  Thus if it is desired to catch every  such  signal,  the

     catching routine must issue another signal call.

     The starred signals in the list above cause core  images  if

     not  caught  and  not ignored.  In C, if func is 0 or 1, the

     action is as described  above.   If  func  is  even,  it  is

     assumed  to  be the address of a function entry point.  When

     the signal occurs, the function will be  called.   A  return

     from the function will simulate the RTI.

     After a fork, the child inherits all signals.  The exec call

     resets all caught signals to default action.


     kill (I, II)


     The error bit (c-bit) is set if the given signal is  out  of

     range.  In C, a -1 indicates an error; 0 indicates success.