vfprintf, _vfprintf_l, vfwprintf, _vfwprintf_l
Write formatted output using a pointer to a list of arguments. More secure versions of these functions exist; see vfprintf_s, _vfprintf_s_l, vfwprintf_s, _vfwprintf_s_l.
int vfprintf( FILE *stream, const char *format, va_list argptr ); int _vfprintf_l( FILE *stream, const char *format, locale_t locale, va_list argptr ); int vfwprintf( FILE *stream, const wchar_t *format, va_list argptr ); int _vfwprintf_l( FILE *stream, const wchar_t *format, locale_t locale, va_list argptr );
Pointer to FILE structure.
Pointer to list of arguments.
The locale to use.
For more information, see Format Specifications.
vfprintf and vfwprintf return the number of characters written, not including the terminating null character, or a negative value if an output error occurs. If either stream or format is a null pointer, 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 stream.
vfwprintf is the wide-character version of vfprintf; the two functions behave identically if the stream is opened in ANSI mode. vfprintf 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.
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 & _MBCS not defined||_MBCS defined||_UNICODE defined|
|Routine||Required header||Optional headers|
|vfprintf, _vfprintf_l||<stdio.h> and <stdarg.h>||<varargs.h>*|
|vfwprintf, _vfwprintf_l||<stdio.h> or <wchar.h>, and <stdarg.h>||<varargs.h>*|
* Required for UNIX V compatibility.
For additional compatibility information, see Compatibility.
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