Rediger

Del via

_vprintf_p, _vprintf_p_l, _vwprintf_p, _vwprintf_p_l

  • Artikkel

Writes formatted output by using a pointer to a list of arguments, and enables specification of the order in which the arguments are used.

Syntax

int _vprintf_p(
   const char *format,
   va_list argptr
);
int _vprintf_p_l(
   const char *format,
   _locale_t locale,
   va_list argptr
);
int _vwprintf_p(
   const wchar_t *format,
   va_list argptr
);
int _vwprintf_p_l(
   const wchar_t *format,
   _locale_t locale,
   va_list argptr
);

Parameters

format
Format specification.

argptr
Pointer to list of arguments.

locale
The locale to use.

For more information, see Format specification syntax.

Return value

_vprintf_p and _vwprintf_p return the number of characters written, not including the terminating null character, or a negative value if an output error occurs.

Remarks

Each of these functions takes a pointer to an argument list, then formats and writes the given data to stdout. These functions differ from vprintf_s and vwprintf_s only in that they support the ability to specify the order in which the arguments are used. For more information, see printf_p Positional Parameters.

_vwprintf_p is the wide-character version of _vprintf_p; the two functions behave identically if the stream is opened in ANSI mode. _vprintf_p 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.

Important

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`.

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.

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_vtprintf_p _vprintf_p _vprintf_p _vwprintf_p
_vtprintf_p_l _vprintf_p_l _vprintf_p_l _vwprintf_p_l

Requirements

Routine Required header Optional headers
_vprintf_p, _vprintf_p_l <stdio.h> and <stdarg.h> <varargs.h>*
_vwprintf_p, _vwprintf_p_l <stdio.h> or <wchar.h>, and <stdarg.h> <varargs.h>*

* Required for UNIX V compatibility.

The console isn't 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 more compatibility information, see Compatibility.

See also

Stream I/O
vprintf functions
_fprintf_p, _fprintf_p_l, _fwprintf_p, _fwprintf_p_l
_printf_p, _printf_p_l, _wprintf_p, _wprintf_p_l
_sprintf_p, _sprintf_p_l, _swprintf_p, _swprintf_p_l
vsprintf_s, _vsprintf_s_l, vswprintf_s, _vswprintf_s_l
va_arg, va_copy, va_end, va_start
_vfprintf_p, _vfprintf_p_l, _vfwprintf_p, _vfwprintf_p_l
_printf_p, _printf_p_l, _wprintf_p, _wprintf_p_l
printf_p Positional Parameters