_vcprintf_p, _vcprintf_p_l, _vcwprintf_p, _vcwprintf_p_l

Writes formatted output to the console by using a pointer to a list of arguments, and supports positional parameters in the format string.

Important

This API cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.

Syntax

int _vcprintf_p(
   const char* format,
   va_list argptr
);
int _vcprintf_p_l(
   const char* format,
   _locale_t locale,
   va_list argptr
);
int _vcwprintf_p(
   const wchar_t* format,
   va_list argptr
);
int _vcwprintf_p_l(
   const wchar_t* format,
   _locale_t locale,
   va_list argptr
);

Parameters

format
The format specification.

argptr
A pointer to a list of arguments.

locale
The locale to use.

For more information, see Format specification syntax: printf and wprintf functions.

Return value

The number of characters that are written, or a negative value if an output error occurs. If format is a null pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, errno is set to EINVAL, and -1 is returned.

Remarks

Each of these functions takes a pointer to an argument list, and then uses the _putch function to format and write the given data to the console. (_vcwprintf_p uses _putwch instead of _putch. _vcwprintf_p is the wide-character version of _vcprintf_p. It takes a wide-character string as an argument.)

The versions of these functions that have the _l suffix are identical except that they use the locale parameter that's passed in instead of the current locale.

Each argument (if any) is converted and is output according to the corresponding format specification in format. The format specification supports positional parameters so that you can specify the order in which the arguments are used in the format string. For more information, see printf_p Positional Parameters.

These functions don't translate line-feed characters on output into carriage return-line feed (CR-LF) combinations.

Important

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

These functions validate the input pointer and the format string. If format or argument is NULL, or if the format string contains invalid formatting characters, these functions invoke the invalid parameter handler, as described in Parameter validation. If execution is allowed to continue, these functions return -1 and set errno to EINVAL.

Generic-text routine mappings

Tchar.h routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_vtcprintf_p	_vcprintf_p	_vcprintf_p	_vcwprintf_p
_vtcprintf_p_l	_vcprintf_p_l	_vcprintf_p_l	_vcwprintf_p_l

Requirements

Routine	Required header
_vcprintf_p, _vcprintf_p_l	<conio.h> and <stdarg.h>
_vcwprintf_p, _vcwprintf_p_l	<conio.h> and <stdarg.h>

For more compatibility information, see Compatibility.

Important

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.

Example

// crt_vcprintf_p.c
// compile with: /c
#include <conio.h>
#include <stdarg.h>

// An error formatting function that's used to print to the console.
int eprintf(const char* format, ...)
{
   va_list args;
   va_start(args, format);
   int result = _vcprintf_p(format, args);
   va_end(args);
   return result;
}

int main()
{
   int n = eprintf("parameter 2 = %2$d; parameter 1 = %1$s\r\n",
      "one", 222);
   _cprintf_s("%d characters printed\r\n");
}

parameter 2 = 222; parameter 1 = one
38 characters printed

See also

Console and port I/O
_cprintf, _cprintf_l, _cwprintf, _cwprintf_l
va_arg, va_copy, va_end, va_start
printf_p Positional Parameters