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Showing content from https://en.cppreference.com/w/cpp/algorithm/../algorithm/../../cpp/../c/io/fwscanf.html below:

wscanf, fwscanf, swscanf, wscanf_s, fwscanf_s, swscanf_s

From cppreference.com

(1)

int wscanf( const wchar_t *format, ... );

(since C95)
(until C99)

int wscanf( const wchar_t *restrict format, ... );

(since C99) (2) int fwscanf( FILE *stream, const wchar_t *format, ... ); (since C95)
(until C99) int fwscanf( FILE *restrict stream,
             const wchar_t *restrict format, ... ); (since C99) (3)

int swscanf( const wchar_t *buffer, const wchar_t *format, ... );

(since C95)
(until C99)

int swscanf( const wchar_t *restrict buffer,
             const wchar_t *restrict format, ... );

(since C99)

int wscanf_s( const wchar_t *restrict format, ...);

(4) (since C11) int fwscanf_s( FILE *restrict stream,
               const wchar_t *restrict format, ...); (5) (since C11)

int swscanf_s( const wchar_t *restrict s,
               const wchar_t *restrict format, ...);

(6) (since C11)

Reads data from the a variety of sources, interprets it according to format and stores the results into given locations.

1)

Reads the data from

stdin

.

2) Reads the data from file stream stream.

3) Reads the data from null-terminated wide string buffer. Reaching the end of the string is equivalent to reaching the end-of-file condition for fwscanf

4-6)

Same as

(1-3)

, except that

%c

,

%s

, and

%[

conversion specifiers each expect two arguments (the usual pointer and a value of type

rsize_t

indicating the size of the receiving array, which may be

1

when reading with a

%lc

into a single wide character) and except that the following errors are detected at runtime and call the currently installed

constraint handler

function:

As all bounds-checked functions, wscanf_s, fwscanf_s, and swscanf_s are only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including <wchar.h>.
[edit] 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 ... - receiving arguments.


The format string consists of

The following format specifiers are available:

Conversion
specifier Explanation Expected
Argument type Length Modifier→ hh h none l ll j z t L Only available since C99→ Yes Yes Yes Yes Yes %

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.

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).

[set ]

Matches a non-empty sequence of character from set of characters.

d

Matches a decimal integer.

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.

u

Matches an unsigned decimal integer.

o

Matches an unsigned octal integer.

x
X

Matches an unsigned hexadecimal integer.

n

Returns the number of characters read so far.

a (C99)
A (C99)
e
E
f
F (C99)
g
G

Matches a floating-point number.

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.

N/A N/A

void**

N/A N/A N/A N/A N/A N/A Notes

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.

All conversion specifiers other than [, c, and n consume and discard all leading whitespace characters (determined as if by calling 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 wcrtomb with an 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 gets.

The correct conversion specifications for the fixed-width integer types (int8_t, etc) are defined in the header <inttypes.h> (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.

[edit] Return value 1-3)

Number of receiving arguments successfully assigned, or

EOF

if read failure occurs before the first receiving argument was assigned.

4-6)

Same as

(1-3)

, except that

EOF

is also returned if there is a runtime constraint violation.

[edit] Example 
#include <stdio.h>
#include <wchar.h>
#include <string.h>
 
#define NUM_VARS   3
#define ERR_READ   2
#define ERR_WRITE  3
 
int main(void) {
    wchar_t state[64];
    wchar_t capital[64];
    unsigned int population = 0;
    int elevation = 0;
    int age = 0;
    float pi = 0;
 
#if INTERACTIVE_MODE
    wprintf(L"Enter state, age, and pi value: ");
    if (wscanf(L"%ls%d%f", state, &age, &pi) != NUM_VARS) {
        fprintf(stderr, "Error reading input.\n");
        return ERR_READ;
    }
#else
    wchar_t* input = L"California 170 3.141592";
    if (swscanf(input, L"%ls%d%f", state, &age, &pi) != NUM_VARS) {
        fprintf(stderr, "Error reading input.\n");
        return ERR_READ;
    }
#endif
    wprintf(L"State: %ls\nAge  : %d years\nPi   : %.5f\n\n", state, age, pi);
 
    FILE* fp = tmpfile();
    if (fp) {
        // write some data to temp file
        if (!fwprintf(fp, L"Mississippi Jackson 420000 807")) {
            fprintf(stderr, "Error writing to file.\n");
            fclose(fp);
            return ERR_WRITE;
        }
        // rewind file pointer
        rewind(fp);
 
        // read data into variables
        fwscanf(fp, L"%ls%ls%u%d", state, capital, &population, &elevation);
        wprintf(L"State  : %ls\nCapital: %ls\nJackson population (in 2020): %u\n"
                L"Highest elevation: %dft\n",
                state, capital, population, elevation);
        fclose(fp);
    }
}

Possible output:

State: California
Age  : 170 years
Pi   : 3.14159
 
State  : Mississippi
Capital: Jackson
Jackson population (in 2020): 420000
Highest elevation: 807ft
[edit] References
[edit] See also

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