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.

HISTORY

       While scanw was implemented in 4BSD, none of the BSD releases used it until 4.4BSD  (in  a
       game).   That  early  version  of  curses  was before the ANSI C standard.  It did not use
       <varargs.h>, though that was available.  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  (or even declare functions) in the <curses.h>
       header until 1992.

       SVr2 documented scanw, wscanw tersely as “scanf through  stdscr”  and  tersely  as  “scanf
       through win”, respectively.

       SVr3  added  mvscanw,  and  mvwscanw,  with  a  three-line  summary  saying that they were
       analogous to scanf(3), explaining that the string which  would  be  output  from  scanf(3)
       would  instead  be  output  using  waddstr  on the given window.  SVr3 also added vwscanw,
       saying that the third parameter is a va_list, defined in <varargs.h>,  and  referring  the
       reader  to  the  manual pages for varargs and vprintf for detailed descriptions.  (Because
       the SVr3 documentation does not mention vscanf, that reference to vprintf may  not  be  an
       error).

       SVr4 added no new variations of scanw, but provided for using <varargs.h> or <stdarg.h> to
       define the va_list type.

       X/Open Curses added vw_scanw to replace  vwscanw,  stating  that  its  va_list  definition
       requires <stdarg.h>.

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

       ncurses(3NCURSES), getstr(3NCURSES), printw(3NCURSES), termcap(3NCURSES), scanf(3).

                                                                                  scanw(3NCURSES)