SIGNAL(3F)                           BSD                            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 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
     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.