1curs_scanw(3X) curs_scanw(3X)
2
6 scanw, wscanw, mvscanw, mvwscanw, vwscanw, vw_scanw - convert formatted
7 input from a curses window
8
10 #include <curses.h>
11 int scanw(const char *fmt, ...);
13 int wscanw(WINDOW *win, const char *fmt, ...);
14 int mvscanw(int y, int x, const char *fmt, ...);
15 int mvwscanw(WINDOW *win, int y, int x, const char *fmt, ...);
16 int vw_scanw(WINDOW *win, const char *fmt, va_list varglist);
18 /* obsolete */
20 int vwscanw(WINDOW *win, const char *fmt, va_list varglist);
21
23 The scanw, wscanw and mvscanw routines are analogous to scanf [see
24 scanf(3)]. The effect of these routines is as though wgetstr were
25 called on the window, and the resulting line used as input for ss‐
26 canf(3). Fields which do not map to a variable in the fmt field are
27 lost.
28 The vwscanw and vw_scanw routines are analogous to vscanf(3). They
30 perform a wscanw using a variable argument list. The third argument is
31 a va_list, a pointer to a list of arguments, as defined in <stdarg.h>.
32
34 vwscanw returns ERR on failure and an integer equal to the number of
35 fields scanned on success.
36 Applications may use the return value from the scanw, wscanw, mvscanw
38 and mvwscanw routines to determine the number of fields which were
39 mapped in the call.
40 Functions with a “mv” prefix first perform a cursor movement using
42 wmove, and return an error if the position is outside the window, or if
43 the window pointer is null.
44
46 While scanw was implemented in 4BSD, none of the BSD releases used it
47 until 4.4BSD (in a game). That early version of curses was before the
48 ANSI C standard. It did not use <varargs.h>, though that was avail‐
49 able. In 1991 (a couple of years after SVr4 was generally available,
50 and after the C standard was published), other developers updated the
51 library, using <stdarg.h> internally in 4.4BSD curses. Even with this
52 improvement, BSD curses did not use function prototypes (or even de‐
53 clare functions) in the <curses.h> header until 1992.
54 SVr2 documented scanw, wscanw tersely as “scanf through stdscr” and
56 tersely as “scanf through win”, respectively.
57 SVr3 added mvscanw, and mvwscanw, with a three-line summary saying that
59 they were analogous to scanf(3), explaining that the string which would
60 be output from scanf(3) would instead be output using waddstr on the
61 given window. SVr3 also added vwscanw, saying that the third parameter
62 is a va_list, defined in <varargs.h>, and referring the reader to the
63 manual pages for varargs and vprintf for detailed descriptions. (Be‐
64 cause the SVr3 documentation does not mention vscanf, that reference to
65 vprintf may not be an error).
66 SVr4 added no new variations of scanw, but provided for using
68 <varargs.h> or <stdarg.h> to define the va_list type.
69 X/Open Curses added vw_scanw to replace vwscanw, stating that its
71 va_list definition requires <stdarg.h>.
72
74 In this implementation, vw_scanw and vwscanw are equivalent, to support
75 legacy applications. However, the latter (vwscanw) is obsolete:
76 • The XSI Curses standard, Issue 4 described these functions, noting
78 that the function vwscanw is marked TO BE WITHDRAWN, and is to be
79 replaced by a function vw_scanw using the <stdarg.h> interface.
80 • The Single Unix Specification, Version 2 states that vw_scanw is
82 preferred to vwscanw since the latter requires including
83 <varargs.h>, which cannot be used in the same file as <stdarg.h>.
84 This implementation uses <stdarg.h> for both, because that header
85 is included in <curses.h>.
86 • X/Open Curses, Issue 5 (December 2007) marked vwscanw (along with
88 vwprintw and the termcap interface) as withdrawn.
89 Both XSI and The Single Unix Specification, Version 2 state that these
91 functions return ERR or OK.
92 • Since the underlying scanf(3) can return the number of items
94 scanned, and the SVr4 code was documented to use this feature, this
95 is probably an editing error which was introduced in XSI, rather
96 than being done intentionally.
97 • This implementation returns the number of items scanned, for com‐
99 patibility with SVr4 curses. As of 2018, NetBSD curses also re‐
100 turns the number of items scanned. Both ncurses and NetBSD curses
101 call vsscanf to scan the string, which returns EOF on error.
102 • Portable applications should only test if the return value is ERR,
104 since the OK value (zero) is likely to be misleading.
105 One possible way to get useful results would be to use a "%n" con‐
107 version at the end of the format string to ensure that something
108 was processed.
109
111 curses(3X), curs_getstr(3X), curs_printw(3X), curs_termcap(3X),
112 scanf(3).
113 curs_scanw(3X)