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

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.

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 characters).

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 characters).

Matches a decimal integer.

• The format of the number is the same as expected by std::wcstol with the value 10 for the base argument.

Matches an unsigned binary integer.

• The format of the number is the same as expected by std::wcstoul with the value 2 for the base argument.

Matches an integer.

• The format of the number is the same as expected by std::wcstol with the value 0 for the base argument (base is determined by the first characters parsed).

Matches an unsigned decimal integer.

• The format of the number is the same as expected by std::wcstoul with the value 10 for the base argument.

Matches an unsigned octal integer.

• The format of the number is the same as expected by std::wcstoul with the value 8 for the base argument.

Matches an unsigned hexadecimal integer.

• The format of the number is the same as expected by std::wcstoul with the value 16 for the base argument.

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.

Matches a floating-point number.

• The format of the number is the same as expected by std::wcstof.

Matches implementation defined character sequence defining a pointer.

• printf family of functions should produce the same sequence using %p format specifier.

For every conversion specifier other than n, the longest sequence of input characters which does not exceed any specified field width and which either is exactly what the conversion specifier expects or is a prefix of a sequence it would expect, is what's consumed from the stream. The first character, if any, after this consumed sequence remains unread. If the consumed sequence has length zero or if the consumed sequence cannot be converted as specified above, the matching failure occurs unless end-of-file, an encoding error, or a read error prevented input from the stream, in which case it is an input failure.

Except for the % specifier, the input item (or, for %n, the count of input characters) is first converted to a type appropriate to the conversion specifier. Unless assignment was suppressed with *, the result of the conversion is written into the object pointed to by the next argument that wasn't yet written to. If this object does not have an appropriate type, or if the result of the conversion cannot be represented in the object, the behavior is undefined.

All conversion specifiers other than [, c, and n consume and discard all leading whitespace characters (determined as if by calling std::iswspace) before attempting to parse the input. These consumed characters do not count towards the specified maximum field width.

If the length specifier l is not used, the conversion specifiers c, s, and [ perform wide-to-multibyte character conversion as if by calling std::wcrtomb with an std::mbstate_t object initialized to zero before the first character is converted.

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 (std::int8_t, etc) are defined in the header <cinttypes> (although SCNdMAX, SCNuMAX, etc is synonymous with %jd, %ju, etc).

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.

If a conversion specification is invalid, the behavior is undefined.