std::vwscanf, std::vfwscanf, std::

Defined in header <cwchar>
int vwscanf( const wchar_t * format, std:: va_list vlist ) ;	(1)	(since C++11)
int vfwscanf( std::FILE * stream, const wchar_t * format, std:: va_list vlist ) ;	(2)	(since C++11)
int vswscanf( const wchar_t * buffer, const wchar_t * format, std:: va_list vlist ) ;	(3)	(since C++11)

Reads data from the a variety of sources, interprets it according to format and stores the results into locations defined by vlist

Parameters

stream	-	input file stream to read from
buffer	-	pointer to a null-terminated wide string to read from
format	-	pointer to a null-terminated wide string specifying how to read the input
vlist	-	variable argument list containing the receiving arguments.

The format string consists of

• non-whitespace wide characters except %
• whitespace characters: any single whitespace character in the format string consumes all available consecutive whitespace characters from the input (determined as if by calling iswspace in a loop). Note that there is no difference between "\n", " ", "\t\t"
• conversion specifications. Each conversion specification has the following format:

• introductory % character.

• (optional) assignment-suppressing character *

• (optional) integer number (greater than zero) that specifies maximum field width, that is, the maximum number of characters that the function is allowed to consume when doing the conversion specified by the current conversion specification. Note that %s and %[

• (optional) length modifier

• conversion format specifier.

The following format specifiers are available:

Conversion specifier	Explanation	Argument type
Length modifier →		hh (C++11)	h	(none)	l	ll (C++11)	j (C++11)	z (C++11)	t (C++11)	L
%	Matches literal %.	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
c	Matches a character or a sequence of characters. If a width specifier is used, matches exactly width wide characters (the argument must be a pointer to an array with sufficient room). Unlike %s and %[, does not append the null character to the array.	N/A	N/A	char*	wchar_t*	N/A	N/A	N/A	N/A	N/A
s	Matches a sequence of non-whitespace characters (a string). If width specifier is used, matches up to width or until the first whitespace character, whichever appears first. Always stores a null character in addition to the characters matched (so the argument array must have room for at least width+1
[set]	Matches a non-empty sequence of character from set of characters. If the first character of the set is ^, then all characters not in the set are matched. If the set begins with ] or ^] then the ] character is also included into the set. It is implementation-defined whether the character - in the non-initial position in the scanset may be indicating a range, as in [0-9]. If width specifier is used, matches only up to width. Always stores a null character in addition to the characters matched (so the argument array must have room for at least width+1
d	Matches a decimal integer. The format of the number is the same as expected by wcstol with the value 10 for the base	signed char* or unsigned char*	signed short* or unsigned short*	signed int* or unsigned int*	signed long* or unsigned long*	signed long long* or unsigned long long*	intmax_t* or uintmax_t*	size_t*	ptrdiff_t*	N/A
i	Matches an integer. The format of the number is the same as expected by wcstol with the value ​0​ for the base
u	Matches an unsigned decimal integer. The format of the number is the same as expected by wcstoul with the value 10 for the base
o	Matches an unsigned octal integer. The format of the number is the same as expected by wcstoul with the value 8 for the base
x, X	Matches an unsigned hexadecimal integer. The format of the number is the same as expected by wcstoul with the value 16 for the base
n	Returns the number of characters read so far. No input is consumed. Does not increment the assignment count. If the specifier has assignment-suppressing operator defined, the behavior is undefined
a, A(C++11) e, E f, F g, G	Matches a floating-point number. The format of the number is the same as expected by wcstof	N/A	N/A	float*	double*	N/A	N/A	N/A	N/A	long double*
p	Matches implementation defined character sequence defining a pointer. printf family of functions should produce the same sequence using %p format specifier	N/A	N/A	void**	N/A	N/A	N/A	N/A	N/A	N/A

For every conversion specifier other than n

All conversion specifiers other than [, c, and n consume and discard all leading whitespace characters (determined as if by calling iswspace

If the length specifier l is not used, the conversion specifiers c, s, and [ perform wide-to-multibyte character conversion as if by calling wcrtomb with an mbstate_t

The conversion specifiers s and [ always store the null terminator in addition to the matched characters. The size of the destination array must be at least one greater than the specified field width. The use of %s or %[, without specifying the destination array size, is as unsafe as std::gets

The correct conversion specifications for the fixed-width integer types (int8_t, etc) are defined in the header <cinttypes> (although SCNdMAX, SCNuMAX, etc is synonymous with %jd, %ju

There is a sequence point after the action of each conversion specifier; this permits storing multiple fields in the same "sink" variable.

When parsing an incomplete floating-point value that ends in the exponent with no digits, such as parsing "100er" with the conversion specifier %f, the sequence "100e" (the longest prefix of a possibly valid floating-point number) is consumed, resulting in a matching error (the consumed sequence cannot be converted to a floating-point number), with "r" remaining. Some existing implementations do not follow this rule and roll back to consume only "100", leaving "er", e.g. glibc bug 1765

A conversion specification must be valid. Otherwise, the behavior is undefined.

Return value

Number of arguments successfully read, or EOF if failure occurs.

Example

This section is incomplete Reason: no example

See also

wscanffwscanfswscanf	reads formatted wide character input from stdin, a file stream or a buffer (function)
C documentation for vwscanf, vfwscanf, vswscanf