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vprintf_s, _vprintf_s_l, vwprintf_s, _vwprintf_s_l

Write formatted output using a pointer to a list of arguments. These are versions of vprintf, _vprintf_l, vwprintf, _vwprintf_l with 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.

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.

Security note Security Note

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










Required header

Optional headers

vprintf_s , _vprintf_s_l

<stdio.h> and <stdarg.h>


vwprintf_s , _vwprintf_s_l

<stdio.h> or <wchar.h>, and <stdarg.h>


* Required for UNIX V compatibility.

The console is not supported in Windows Store apps. The standard stream handles associated with the console, stdin, stdout, and stderr, must be redirected before C run-time functions can use them in Windows Store apps. For additional compatibility information, see Compatibility in the Introduction.

© 2015 Microsoft