SIGNAL(3F)          RISC/os Reference Manual           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 han-
     dling 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 particular, this is how previ-
     ously 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 sig-
     nal".

     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.









                        Printed 11/19/92                   Page 1