vprintf_s, _vprintf_s_l, vwprintf_s, _vwprintf_s_l

Writes formatted output by using a pointer to a list of arguments. These versions of vprintf, _vprintf_l, vwprintf, _vwprintf_l have security enhancements, as described in Security Features in the CRT.


int vprintf_s(
   const char *format,
   va_list argptr
int _vprintf_s_l(
   const char *format,
   locale_t locale,
   va_list argptr
int vwprintf_s(
   const wchar_t *format,
   va_list argptr
int _vwprintf_s_l(
   const wchar_t *format,
   locale_t locale,
   va_list argptr


Format specification.

Pointer to list of arguments.

The locale to use.

For more information, see Format Specifications.

Return Value

vprintf_s and vwprintf_s return the number of characters written, not including the terminating null character, or a negative value if an output error occurs. If 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, the functions return -1 and set errno to EINVAL.

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


Each of these functions takes a pointer to an argument list, then formats and writes the given data to stdout.

The secure versions of these functions differ from vprintf and vwprintf only in that the secure versions check that the format string contains valid formatting characters.

vwprintf_s is the wide-character version of vprintf_s; the two functions behave identically if the stream is opened in ANSI mode. vprintf_s doesn't currently support output into a UNICODE stream.

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.


Ensure that format is not a user-defined string. For more information, see Avoiding Buffer Overruns.

Generic-Text Routine Mappings

TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined
_vtprintf_s vprintf_s vprintf_s vwprintf_s
_vtprintf_s_l _vprintf_s_l _vprintf_s_l _vwprintf_s_l


Routine Required header Optional headers
vprintf_s, _vprintf_s_l <stdio.h> and <stdarg.h> <varargs.h>*
vwprintf_s, _vwprintf_s_l <stdio.h> or <wchar.h>, and <stdarg.h> <varargs.h>*

* Required for UNIX V compatibility.

The console is not 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 additional compatibility information, see Compatibility.

See also

Stream I/O
vprintf Functions
fprintf, _fprintf_l, fwprintf, _fwprintf_l
printf, _printf_l, wprintf, _wprintf_l
sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l
va_arg, va_copy, va_end, va_start