curs_scanw(3) curs_scanw(3)
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:
o 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.
o 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>.
o 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.
o 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.
o 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.
o 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(3)
ncurses 6.4 - Generated Tue Jan 3 13:17:46 CST 2023