vsscanf, vswscanf

Reads formatted data from a string. More secure versions of these functions are available; see vsscanf_s, vswscanf_s.

Syntax

int vsscanf(
   const char *buffer,
   const char *format,
   va_list arglist
);
int vswscanf(
   const wchar_t *buffer,
   const wchar_t *format,
   va_list arglist
);

Parameters

buffer
Stored data

format
Format-control string. For more information, see Format specification fields: scanf and wscanf functions.

arglist
Variable argument list.

Return value

Each of these functions 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. The return value is EOF for an error or if the end of the string is reached before the first conversion.

If buffer or 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 -1 and set errno to EINVAL.

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

Remarks

The vsscanf function reads data from buffer into the locations that are given by each argument in the arglist argument list. Every argument in the list must be a pointer to a variable that has a type that corresponds to a type specifier in format. The format argument controls the interpretation of the input fields and has the same form and function as the format argument for the scanf function. If copying takes place between strings that overlap, the behavior is undefined.

Important

When you use vsscanf 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.

vswscanf is a wide-character version of vsscanf; the arguments to vswscanf are wide-character strings. vsscanf doesn't handle multibyte hexadecimal characters. vswscanf doesn't handle Unicode full-width hexadecimal or "compatibility zone" characters. Otherwise, vswscanf and vsscanf behave identically.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_vstscanf	vsscanf	vsscanf	vswscanf

Requirements

Routine	Required header
vsscanf	<stdio.h>
vswscanf	<stdio.h> or <wchar.h>

For more compatibility information, see Compatibility.

Example

// crt_vsscanf.c
// compile with: /W3
// This program uses vsscanf to read data items
// from a string named tokenstring, then displays them.

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

int call_vsscanf(char *tokenstring, char *format, ...)
{
    int result;
    va_list arglist;
    va_start(arglist, format);
    result = vsscanf(tokenstring, format, arglist);
    va_end(arglist);
    return result;
}

int main( void )
{
    char  tokenstring[] = "15 12 14...";
    char  s[81];
    char  c;
    int   i;
    float fp;

    // Input various data from tokenstring:
    // max 80 character string:
    call_vsscanf(tokenstring, "%80s", s);
    call_vsscanf(tokenstring, "%c", &c);
    call_vsscanf(tokenstring, "%d", &i);
    call_vsscanf(tokenstring, "%f", &fp);

    // Output the data read
    printf("String    = %s\n", s);
    printf("Character = %c\n", c);
    printf("Integer:  = %d\n", i);
    printf("Real:     = %f\n", fp);
}

String    = 15
Character = 1
Integer:  = 15
Real:     = 15.000000

See also

Stream I/O
scanf, _scanf_l, wscanf, _wscanf_l
sscanf, _sscanf_l, swscanf, _swscanf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
vsscanf_s, vswscanf_s