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<H1 class="no-header">curs_scanw 3x 2025-07-05 ncurses 6.6 Library calls</H1>
<PRE>
<STRONG><A HREF="curs_scanw.3x.html">curs_scanw(3x)</A></STRONG> Library calls <STRONG><A HREF="curs_scanw.3x.html">curs_scanw(3x)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
<STRONG>scanw</STRONG>, <STRONG>wscanw</STRONG>, <STRONG>mvscanw</STRONG>, <STRONG>mvwscanw</STRONG>, <STRONG>vwscanw</STRONG>, <STRONG>vw_scanw</STRONG> - read formatted
input from a <EM>curses</EM> window
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
<STRONG>#include</STRONG> <STRONG><curses.h></STRONG>
<STRONG>int</STRONG> <STRONG>scanw(const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>fmt</EM><STRONG>,</STRONG> <STRONG>...);</STRONG>
<STRONG>int</STRONG> <STRONG>wscanw(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>fmt</EM><STRONG>,</STRONG> <STRONG>...);</STRONG>
<STRONG>int</STRONG> <STRONG>mvscanw(int</STRONG> <EM>y</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>x</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>fmt</EM><STRONG>,</STRONG> <STRONG>...);</STRONG>
<STRONG>int</STRONG> <STRONG>mvwscanw(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>y</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>x</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>fmt</EM><STRONG>,</STRONG> <STRONG>...);</STRONG>
<STRONG>int</STRONG> <STRONG>vw_scanw(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>fmt</EM><STRONG>,</STRONG> <STRONG>va_list</STRONG> <EM>varglist</EM><STRONG>);</STRONG>
<EM>/*</EM> <EM>obsolete</EM> <EM>*/</EM>
<STRONG>int</STRONG> <STRONG>vwscanw(WINDOW</STRONG> <STRONG>*</STRONG><EM>win</EM><STRONG>,</STRONG> <STRONG>const</STRONG> <STRONG>char</STRONG> <STRONG>*</STRONG><EM>fmt</EM><STRONG>,</STRONG> <STRONG>va_list</STRONG> <EM>varglist</EM><STRONG>);</STRONG>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
<STRONG>scanw</STRONG>, <STRONG>wscanw</STRONG>, <STRONG>mvscanw</STRONG>, and <STRONG>mvwscanw</STRONG> are analogous to <STRONG>scanf(3)</STRONG>. In
effect, they call <STRONG><A HREF="curs_getstr.3x.html">wgetstr(3x)</A></STRONG> with <EM>win</EM> (or <STRONG>stdscr</STRONG>) as its first
argument, then attempt conversion of the resulting string with
<STRONG>vsscanf(3)</STRONG>. Fields in the string that do not map to a variable in the
<EM>fmt</EM> parameter are discarded.
<STRONG>vwscanw</STRONG> and <STRONG>vw_scanw</STRONG> are analogous to <STRONG>vscanf(3)</STRONG>, and perform a <STRONG>wscanw</STRONG>
using a variable argument list. The third argument is a <EM>va</EM><STRONG>_</STRONG><EM>list</EM>, a
pointer to a list of arguments, as defined in <EM>stdarg.h</EM>.
</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
These functions return <STRONG>ERR</STRONG> upon failure and otherwise a count of
successful conversions; this quantity may be zero.
In <EM>ncurses</EM>, failure occurs if <STRONG>vsscanf(3)</STRONG> returns <STRONG>EOF</STRONG>, or if the window
pointer <EM>win</EM> is null.
Functions prefixed with "mv" first perform cursor movement and fail if
the position (<EM>y</EM>, <EM>x</EM>) is outside the window boundaries.
</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
No wide character counterpart functions are defined by the "wide"
<EM>ncurses</EM> configuration nor by any standard. They are unnecessary: to
retrieve and convert a wide-character string from a <EM>curses</EM> terminal
keyboard, use these functions with the <STRONG>scanf(3)</STRONG> conversions "%lc" and
"%ls" for wide characters and strings, respectively.
<EM>ncurses</EM> implements <STRONG>vsscanf(3)</STRONG> internally if it is unavailable when the
library is configured.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
X/Open Curses Issue 4 describes these functions. It specifies no error
conditions for them.
<EM>ncurses</EM> defines <STRONG>vw_scanw</STRONG> and <STRONG>vwscanw</STRONG> identically to support legacy
applications. However, the latter is obsolete.
<STRONG>o</STRONG> X/Open Curses Issue 4 Version 2 (1996), marked <STRONG>vwscanw</STRONG> as requiring
<EM>varargs.h</EM> and "TO BE WITHDRAWN", and specified <STRONG>vw_scanw</STRONG> using the
<EM>stdarg.h</EM> interface.
<STRONG>o</STRONG> X/Open Curses Issue 5, Draft 2 (December 2007) marked <STRONG>vwscanw</STRONG>
(along with <STRONG>vwscanw</STRONG> and the <EM>termcap</EM> interface) as withdrawn. After
incorporating review comments, this became X/Open Curses Issue 7
(2009).
<STRONG>o</STRONG> <EM>ncurses</EM> provides <STRONG>vwscanw</STRONG>, but marks it as deprecated.
X/Open Curses Issues 4 and 7 both state that these functions return <STRONG>ERR</STRONG>
or <STRONG>OK</STRONG>. This is likely an erratum.
<STRONG>o</STRONG> Since the underlying <STRONG>scanf(3)</STRONG> returns the number of successful
conversions, and SVr4 <EM>curses</EM> was documented to use this feature,
this may have been an editorial solecism introduced by X/Open,
rather than an intentional change.
<STRONG>o</STRONG> This implementation retains compatibility with SVr4 <EM>curses</EM>. As of
2018, NetBSD <EM>curses</EM> also returns the number of successful
conversions. Both <EM>ncurses</EM> and NetBSD <EM>curses</EM> call <STRONG>vsscanf(3)</STRONG> to
scan the string, which returns <STRONG>EOF</STRONG> on error.
<STRONG>o</STRONG> Portable applications should test only if the return value is <STRONG>ERR</STRONG>,
and not compare it to <STRONG>OK</STRONG>, 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.
</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
4BSD (1980) introduced <EM>wscanw</EM> and its variants. It implemented all as
functions, not macros; this initial distribution of <EM>curses</EM> preceded the
ANSI C standard of 1989, prior to which a variadic macro facility was
not widely available. <EM>scanw</EM> went unused in Berkeley distributions
until 4.3BSD-Reno (1990), which employed it in a game. 4BSD's <EM>wscanw</EM>
did not use <EM>varargs.h</EM>, 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 <EM>stdarg.h</EM> internally in 4.4BSD <EM>curses</EM>. Even
with this improvement, BSD <EM>curses</EM> did not use function prototypes (nor
even declare functions) in <EM>curses.h</EM> until 1992.
4BSD documented <EM>scanw</EM> and <EM>wscanw</EM> tersely as "scanf through <EM>stdscr</EM>" and
"scanf through <EM>win</EM>", respectively. SVr3 (1987) stated
[t]hese routines correspond to <STRONG>scanf(3S)</STRONG>, as do their arguments
and return values. <EM>wgetstr</EM>() is called on the window, and the
resulting line is used as input for the scan.
SVr3 added <EM>vwscanw</EM>, describing its third parameter as a <EM>va</EM><STRONG>_</STRONG><EM>list</EM>,
defined in <EM>varargs.h</EM>, and referred the reader to the manual pages for
<EM>varargs</EM> and <EM>vprintf</EM> for detailed descriptions. (Because SVr3
documentation does not mention <EM>vscanf</EM>, the reference to <EM>vprintf</EM> might
not be an error).
SVr4 (1989) introduced no new variations of <EM>scanw</EM>, but provided for
using either <EM>varargs.h</EM> or <EM>stdarg.h</EM> to define the <EM>va</EM><STRONG>_</STRONG><EM>list</EM> type.
X/Open Curses Issue 4 (1995) defined <EM>vw</EM><STRONG>_</STRONG><EM>scanw</EM> to replace <EM>vwscanw</EM>,
stating that its <EM>va</EM><STRONG>_</STRONG><EM>list</EM> type is defined in <EM>stdarg.h</EM>.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
<STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="curs_getstr.3x.html">curs_getstr(3x)</A></STRONG>, <STRONG><A HREF="curs_printw.3x.html">curs_printw(3x)</A></STRONG>, <STRONG>scanf(3)</STRONG>, <STRONG>vscanf(3)</STRONG>
ncurses 6.6 2025-07-05 <STRONG><A HREF="curs_scanw.3x.html">curs_scanw(3x)</A></STRONG>
</PRE>
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<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
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