vwscanw returns ERR on failure and an integer equal to the number of fields scanned on success.
Applications may use the return value from the scanw, wscanw, mvscanw and mvwscanw routines to determine the number of fields which were mapped in the call.
The XSI Curses standard, Issue 4 describes these functions. The function vwscanw is marked TO BE WITHDRAWN, and is to be replaced by a function vw_scanw using the <stdarg.h> interface.
curses(3), curs_getstr(3), curs_printw(3), scanf(3S)