_sprintf_p, _sprintf_p_l, _swprintf_p, _swprintf_p_l

Write formatted data to a string with the ability to specify the order that the parameters are used in the format string.


int _sprintf_p(
   char *buffer,
   size_t sizeOfBuffer,
   const char *format [,
int _sprintf_p_l(
   char *buffer,
   size_t sizeOfBuffer,
   const char *format,
   _locale_t locale [,
int _swprintf_p(
   wchar_t *buffer,
   size_t sizeOfBuffer,
   const wchar_t *format [,
int _swprintf_p_l(
   wchar_t *buffer,
   size_t sizeOfBuffer,
   const wchar_t *format,
   _locale_t locale [,


Storage location for output

Maximum number of characters to store.

Format-control string.

Optional arguments to the format string.

The locale to use.

For more information, see Format specification syntax.

Return value

The number of characters written, or -1 if an error occurred.


The _sprintf_p function formats and stores a series of characters and values in buffer. Each argument in the argument_list (if any) is converted and output according to the corresponding format specification in format. The format argument uses the format specification syntax for printf and wprintf functions. A null character is appended after the last character written. If copying occurs between strings that overlap, the behavior is undefined. The difference between _sprintf_p and sprintf_s is that _sprintf_p supports positional parameters, which allows specifying the order in which the arguments are used in the format string. For more information, see printf_p Positional Parameters.

_swprintf_p is a wide-character version of _sprintf_p; the pointer arguments to _swprintf_p are wide-character strings. Detection of encoding errors in _swprintf_p may differ from the detection in _sprintf_p. _swprintf_p and fwprintf_p behave identically except that _swprintf_p writes output to a string rather than to a destination of type FILE, and _swprintf_p requires the count parameter to specify the maximum number of characters to be written. The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current thread locale.

_sprintf_p returns the number of bytes stored in buffer, not counting the terminating null character. _swprintf_p returns the number of wide characters stored in buffer, not counting the terminating null wide character. If buffer or format is a null pointer, or if the format string contains invalid formatting characters, 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.


Starting in Windows 10 version 2004 (build 19041), the printf family of functions prints exactly representable floating point numbers according to the IEEE 754 rules for rounding. In previous versions of Windows, exactly representable floating point numbers ending in '5' would always round up. IEEE 754 states that they must round to the closest even digit (also known as "Banker's Rounding"). For example, both printf("%1.0f", 1.5) and printf("%1.0f", 2.5) should round to 2. Previously, 1.5 would round to 2 and 2.5 would round to 3. This change only affects exactly representable numbers. For example, 2.35 (which, when represented in memory, is closer to 2.35000000000000008) continues to round up to 2.4. Rounding done by these functions now also respects the floating point rounding mode set by fesetround. Previously, rounding always chose FE_TONEAREST behavior. This change only affects programs built using Visual Studio 2019 version 16.2 and later. To use the legacy floating point rounding behavior, link with 'legacy_stdio_float_rounding.obj`.

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_stprintf_p _sprintf_p _sprintf_p _swprintf_p
_stprintf_p_l _sprintf_p_l _sprintf_p_l _swprintf_p_l


Routine Required header
_sprintf_p, _sprintf_p_l <stdio.h>
_swprintf_p, _swprintf_p_l <stdio.h> or <wchar.h>

For more compatibility information, see Compatibility.

Example: Use _sprintf_p to format data

// crt_sprintf_p.c
// This program uses _sprintf_p to format various
// data and place them in the string named buffer.

#include <stdio.h>

int main( void )
    char     buffer[200],
            s[] = "computer", c = 'l';
    int      i = 35,
    float    fp = 1.7320534f;

    // Format and print various data:
    j  = _sprintf_p( buffer, 200,
                     "   String:    %s\n", s );
    j += _sprintf_p( buffer + j, 200 - j,
                     "   Character: %c\n", c );
    j += _sprintf_p( buffer + j, 200 - j,
                     "   Integer:   %d\n", i );
    j += _sprintf_p( buffer + j, 200 - j,
                     "   Real:      %f\n", fp );

    printf( "Output:\n%s\ncharacter count = %d\n",
            buffer, j );
   String:    computer
   Character: l
   Integer:   35
   Real:      1.732053

character count = 79

Example: Error code handling

// crt_swprintf_p.c
// This is the wide character example which
// also demonstrates _swprintf_p returning
// error code.
#include <stdio.h>

#define BUFFER_SIZE 100

int main( void )
    wchar_t buffer[BUFFER_SIZE];
    int     len;

    len = _swprintf_p(buffer, BUFFER_SIZE, L"%2$s %1$d",
                      0, L" marbles in your head.");
    _printf_p( "Wrote %d characters\n", len );

    // _swprintf_p fails because string contains WEOF (\xffff)
    len = _swprintf_p(buffer, BUFFER_SIZE, L"%s",
                      L"Hello\xffff world" );
    _printf_p( "Wrote %d characters\n", len );
Wrote 24 characters
Wrote -1 characters

See also

Stream I/O
_fprintf_p, _fprintf_p_l, _fwprintf_p, _fwprintf_p_l
fprintf, _fprintf_l, fwprintf, _fwprintf_l
_printf_p, _printf_p_l, _wprintf_p, _wprintf_p_l
printf, _printf_l, wprintf, _wprintf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
scanf, _scanf_l, wscanf, _wscanf_l
sscanf, _sscanf_l, swscanf, _swscanf_l
sscanf_s, _sscanf_s_l, swscanf_s, _swscanf_s_l
vprintf functions
printf_p Positional Parameters