https://invisible-island.net/ncurses/man/
curs_scanw(3x) Library calls curs_scanw(3x)
scanw, wscanw, mvscanw, mvwscanw, vwscanw, vw_scanw - read formatted
input from a curses window
#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);
scanw, wscanw, mvscanw, and mvwscanw are analogous to scanf(3). In
effect, they call wgetstr(3x) with win (or stdscr) as its first
argument, then attempt conversion of the resulting string with
vsscanf(3). Fields in the string that do not map to a variable in the
fmt parameter are discarded.
vwscanw and vw_scanw are analogous to vscanf(3), and 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.
These functions return ERR upon failure and otherwise a count of
successful conversions; this quantity may be zero.
In ncurses, failure occurs if vsscanf(3) returns EOF, or if the window
pointer win is null.
Functions prefixed with "mv" first perform cursor movement and fail if
the position (y, x) is outside the window boundaries.
No wide character counterpart functions are defined by the "wide"
ncurses configuration nor by any standard. They are unnecessary: to
retrieve and convert a wide-character string from a curses terminal
keyboard, use these functions with the scanf(3) conversions "%lc" and
"%ls" for wide characters and strings, respectively.
ncurses implements vsscanf(3) internally if it is unavailable when the
library is configured.
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
ncurses defines vw_scanw and vwscanw identically to support legacy
applications. However, the latter is obsolete.
o X/Open Curses Issue 4 Version 2 (1996), marked vwscanw as requiring
varargs.h and "TO BE WITHDRAWN", and specified vw_scanw using the
stdarg.h interface.
o X/Open Curses Issue 5, Draft 2 (December 2007) marked vwscanw
(along with vwscanw and the termcap interface) as withdrawn. After
incorporating review comments, this became X/Open Curses Issue 7
(2009).
o ncurses provides vwscanw, but marks it as deprecated.
X/Open Curses Issues 4 and 7 both state that these functions return ERR
or OK. This is likely an erratum.
o Since the underlying scanf(3) returns the number of successful
conversions, and SVr4 curses was documented to use this feature,
this may have been an editorial solecism introduced by X/Open,
rather than an intentional change.
o This implementation retains compatibility with SVr4 curses. As of
2018, NetBSD curses also returns the number of successful
conversions. Both ncurses and NetBSD curses call vsscanf(3) to
scan the string, which returns EOF on error.
o Portable applications should test only if the return value is ERR,
and not compare it to OK, since that value (zero) might be
misleading.
One portable way to get useful results would be to use a "%n"
conversion at the end of the format string, and check the value of
the corresponding variable to determine how many conversions
succeeded.
4BSD (1980) introduced wscanw and its variants. It implemented all as
functions, not macros; this initial distribution of curses preceded the
ANSI C standard of 1989, prior to which a variadic macro facility was
not widely available. scanw went unused in Berkeley distributions
until 4.3BSD-Reno (1990), which employed it in a game. 4BSD's wscanw
did not use varargs.h, which had been available since Seventh Edition
Unix (1979). In 1991 (a couple of years after SVr4 was generally
available, and after the C standard was published), other developers
updated the library, using stdarg.h internally in 4.4BSD curses. Even
with this improvement, BSD curses did not use function prototypes (nor
even declare functions) in curses.h until 1992.
4BSD documented scanw and wscanw tersely as "scanf through stdscr" and
"scanf through win", respectively. SVr3 (1987) stated
[t]hese routines correspond to scanf(3S), as do their arguments
and return values. wgetstr() is called on the window, and the
resulting line is used as input for the scan.
SVr3 added vwscanw, describing its third parameter as a va_list,
defined in varargs.h, and referred the reader to the manual pages for
varargs and vprintf for detailed descriptions. (Because SVr3
documentation does not mention vscanf, the reference to vprintf might
not be an error).
SVr4 (1989) introduced no new variations of scanw, but provided for
using either varargs.h or stdarg.h to define the va_list type.
X/Open Curses Issue 4 (1995), defined vw_scanw to replace vwscanw,
stating that its va_list type is defined in stdarg.h.
curses(3x), curs_getstr(3x), curs_printw(3x), scanf(3), vscanf(3)
ncurses 6.5 2025-04-05 curs_scanw(3x)