vscanf, vwscanf

Reads formatted data from the standard input stream. More secure versions of these functions are available; see vscanf_s, vwscanf_s.

Syntax

int vscanf(
   const char *format,
   va_list arglist
);
int vwscanf(
   const wchar_t *format,
   va_list arglist
);

Parameters

format
Format control string.

arglist
Variable argument list.

Return value

Returns the number of fields that are successfully converted and assigned; the return value doesn't include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned.

If format is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, these functions return EOF and set errno to EINVAL.

For information about these and other error codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.

Remarks

The vscanf function reads data from the standard input stream stdin and writes the data into the locations that are given by the arglist argument list. Each argument in the list must be a pointer to a variable of a type that corresponds to a type specifier in format. If copying occurs between strings that overlap, the behavior is undefined.

Important

When you use vscanf to read a string, always specify a width for the %s format (for example, "%32s" instead of "%s"); otherwise, incorrectly formatted input can cause a buffer overrun. As an alternative, you can use vscanf_s, vwscanf_s or fgets.

vwscanf is a wide-character version of vscanf; the format argument to vwscanf is a wide-character string. vwscanf and vscanf behave identically if the stream is opened in ANSI mode. vscanf doesn't support input from a UNICODE stream.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_vtscanf	vscanf	vscanf	vwscanf

For more information, see Format specification fields: scanf and wscanf functions.

Requirements

Routine	Required header
vscanf	<stdio.h>
vwscanf	<stdio.h> or <wchar.h>

The console isn't supported in Universal Windows Platform (UWP) apps. The standard stream handles that are associated with the console, stdin, stdout, and stderr, must be redirected before C run-time functions can use them in UWP apps. For more compatibility information, see Compatibility.

Example

// crt_vscanf.c
// compile with: /W3
// This program uses the vscanf and vwscanf functions
// to read formatted input.

#include <stdio.h>
#include <stdarg.h>

int call_vscanf(char *format, ...)
{
    int result;
    va_list arglist;
    va_start(arglist, format);
    result = vscanf(format, arglist);
    va_end(arglist);
    return result;
}

int call_vwscanf(wchar_t *format, ...)
{
    int result;
    va_list arglist;
    va_start(arglist, format);
    result = vwscanf(format, arglist);
    va_end(arglist);
    return result;
}

int main( void )
{
    int   i, result;
    float fp;
    char  c, s[81];
    wchar_t wc, ws[81];
    result = call_vscanf( "%d %f %c %C %80s %80S", &i, &fp, &c, &wc, s, ws );
    printf( "The number of fields input is %d\n", result );
    printf( "The contents are: %d %f %c %C %s %S\n", i, fp, c, wc, s, ws);
    result = call_vwscanf( L"%d %f %hc %lc %80S %80ls", &i, &fp, &c, &wc, s, ws );
    wprintf( L"The number of fields input is %d\n", result );
    wprintf( L"The contents are: %d %f %C %c %hs %s\n", i, fp, c, wc, s, ws);
}

      71 98.6 h z Byte characters
36 92.3 y n Wide charactersThe number of fields input is 6
The contents are: 71 98.599998 h z Byte characters
The number of fields input is 6
The contents are: 36 92.300003 y n Wide characters

See also

Math and floating-point support
Stream I/O
Locale
fscanf, _fscanf_l, fwscanf, _fwscanf_l
printf, _printf_l, wprintf, _wprintf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
sscanf, _sscanf_l, swscanf, _swscanf_l
vscanf_s, vwscanf_s