curses bell and screen flash routines
flash routines are used to alert the terminal user. The routine
beep sounds an audible alarm on the terminal, if possible; otherwise it flashes the screen (visible bell). The routine
flash flashes the screen, and if that is not possible, sounds the alert. If neither alert is possible, nothing happens. Nearly all terminals have an audible alert (bell or beep), but only some can flash the screen.
RETURN VALUE These routines return
OK if they succeed in beeping or flashing,
EXTENSIONS SVr4's beep and flash routines always returned
OK, so it was not possible to tell when the beep or flash failed.
PORTABILITY These functions are described in the XSI Curses standard, Issue 4. Like SVr4, it specifies that they always return