


      SIGNAL(3F)                  (bsd 4.2)                  SIGNAL(3F)



      NAME
           signal - change the action for a signal

      SYNTAX
           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 particular, 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
           ssignal(3C), kill(3F), kill(1)

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













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