curs_scanw(3X)                                                  curs_scanw(3X)

NAME
       scanw, wscanw, mvscanw, mvwscanw, vwscanw, vw_scanw - convert formatted
       input from a curses window

SYNOPSIS
       #include <curses.h>

       int scanw(const char *fmt, ...);
       int wscanw(WINDOW *win, const char *fmt, ...);
       int mvscanw(int y, int x, const char *fmt, ...);
       int mvwscanw(WINDOW *win, int y, int x, const char *fmt, ...);
       int vw_scanw(WINDOW *win, const char *fmt, va_list varglist);

       /* obsolete */
       int vwscanw(WINDOW *win, const char *fmt, va_list varglist);

DESCRIPTION
       The scanw, wscanw and mvscanw routines are analogous to scanf [see
       scanf(3)].  The effect of these routines is as though wgetstr were
       called on the window, and the resulting line used as input for
       sscanf(3).  Fields which do not map to a variable in the fmt field are
       lost.

       The vwscanw and vw_scanw routines are analogous to vscanf(3).  They
       perform a wscanw using a variable argument list.  The third argument is
       a va_list, a pointer to a list of arguments, as defined in <stdarg.h>.

RETURN VALUE
       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.

       Functions with a "mv" prefix first perform a cursor movement using
       wmove, and return an error if the position is outside the window, or if
       the window pointer is null.

PORTABILITY
       In this implementation, vw_scanw and vwscanw are equivalent, to support
       legacy applications.  However, the latter (vwscanw) is obsolete:

       • The XSI Curses standard, Issue 4 described these functions, noting
           that the function vwscanw is marked TO BE WITHDRAWN, and is to be
           replaced by a function vw_scanw using the <stdarg.h> interface.

       • The Single Unix Specification, Version 2 states that vw_scanw  is
           preferred to vwscanw since the latter requires including
           <varargs.h>, which cannot be used in the same file as <stdarg.h>.
           This implementation uses <stdarg.h> for both, because that header
           is included in <curses.h>.

       • X/Open Curses, Issue 5 (December 2007) marked vwscanw (along with
           vwprintw and the termcap interface) as withdrawn.

       Both XSI and The Single Unix Specification, Version 2 state that these
       functions return ERR or OK.

       • Since the underlying scanf(3) can return the number of items
           scanned, and the SVr4 code was documented to use this feature, this
           is probably an editing error which was introduced in XSI, rather
           than being done intentionally.

       • This implementation returns the number of items scanned, for
           compatibility with SVr4 curses.  As of 2018, NetBSD curses also
           returns the number of items scanned.  Both ncurses and NetBSD
           curses call vsscanf to scan the string, which returns EOF on error.

       • Portable applications should only test if the return value is ERR,
           since the OK value (zero) is likely to be misleading.

           One possible way to get useful results would be to use a "%n"
           conversion at the end of the format string to ensure that something
           was processed.

SEE ALSO
       curses(3X), curs_getstr(3X), curs_printw(3X), curs_termcap(3X),
       scanf(3).

                                                                curs_scanw(3X)