vprintf Functions

Article
04/28/2015

Each of the vprintf functions takes a pointer to an argument list, then formats and writes the given data to a particular destination. The functions differ in the parameter validation performed, whether the functions take wide or single-byte character strings, the output destination, and the support for specifying the order in which parameters are used in the format string.

_vcprintf, _vcwprintf	vfprintf, vfwprintf
_vfprintf_p, _vfprintf_p_l, _vfwprintf_p, _vfwprintf_p_l	vfprintf_s, _vfprintf_s_l, vfwprintf_s, _vfwprintf_s_l
vprintf, vwprintf	_vprintf_p, _vprintf_p_l, _vwprintf_p, _vwprintf_p_l
vprintf_s, _vprintf_s_l, vwprintf_s, _vwprintf_s_l	vsprintf, vswprintf
_vsprintf_p, _vsprintf_p_l, _vswprintf_p, _vswprintf_p_l	vsprintf_s, _vsprintf_s_l, vswprintf_s, _vswprintf_s_l
_vscprintf, _vscprintf_l, _vscwprintf, _vscwprintf_l	_vsnprintf, _vsnwprintf

Remarks

The vprintf functions are similar to their counterpart functions as listed in the following table. However, each vprintf function accepts a pointer to an argument list, whereas each of the counterpart functions accepts an argument list.

These functions format data for output to destinations as follows.

Function	Counterpart function	Output destination	Parameter Validation	Positional Parameter Support
_vcprintf	_cprintf	console	Check for null.	no
_vcwprintf	_cwprintf	console	Check for null.	no
vfprintf	fprintf	Stream	Check for null.	no
vfprintf_p	fprintf_p	Stream	Check for null and valid format.	yes
vfprintf_s	fprintf_s	Stream	Check for null and valid format.	no
vfwprintf	fwprintf	Stream	Check for null.	no
vfwprintf_p	fwprintf_p	Stream	Check for null and valid format.	yes
vfwprintf_s	fwprintf_s	Stream	Check for null and valid format.	no
vprintf	printf	Stdout	Check for null.	no
vprintf_p	printf_p	Stdout	Check for null and valid format.	yes
vprintf_s	printf_s	Stdout	Check for null and valid format.	no
vwprintf	wprintf	Stdout	Check for null.	no
vwprintf_p	wprintf_p	Stdout	Check for null and valid format.	yes
vwprintf_s	wprintf_s	Stdout	Check for null and valid format.	no
vsprintf	sprintf	memory pointed to by buffer	Check for null.	no
vsprintf_p	sprintf_p	memory pointed to by buffer	Check for null and valid format.	yes
vsprintf_s	sprintf_s	memory pointed to by buffer	Check for null and valid format.	no
vswprintf	swprintf	memory pointed to by buffer	Check for null.	no
vswprintf_p	swprintf_p	memory pointed to by buffer	Check for null and valid format.	yes
vswprintf_s	swprintf_s	memory pointed to by buffer	Check for null and valid format.	no
_vscprintf	_vscprintf	memory pointed to by buffer	Check for null.	no
_vscwprintf	_vscwprintf	memory pointed to by buffer	Check for null.	no
_vsnprintf	_snprintf	memory pointed to by buffer	Check for null.	no
_vsnwprintf	_snwprintf	memory pointed to by buffer	Check for null.	no

The argptr argument has type va_list, which is defined in VARARGS.H and STDARG.H. The argptr variable must be initialized by va_start, and may be reinitialized by subsequent va_arg calls; argptr then points to the beginning of a list of arguments that are converted and transmitted for output according to the corresponding specifications in the format argument. format has the same form and function as the format argument for printf. None of these functions invokes va_end. For a more complete description of each vprintf function, see the description of its counterpart function as listed in the preceding table.

_vsnprintf differs from vsprintf in that it writes no more than count bytes to buffer.

The versions of these functions with the w infix in the name are wide-character versions of the corresponding functions without the w infix; in each of these wide-character functions, buffer and format are wide-character strings. Otherwise, each wide-character function behaves identically to its SBCS counterpart function.

The versions of these functions with _s and _p suffixes are the more secure versions. These versions validate the format strings and will generate an exception if the format string is not well formed (for example, if invalid formatting characters are used).

The versions of these functions with the _p suffix provide the ability to specify the order in which the supplied arguments are substituted in the format string. For more information, see printf_p Positional Parameters.

For vsprintf, vswprintf, _vsnprintf and _vsnwprintf, if copying occurs between strings that overlap, the behavior is undefined.

Security Note
Ensure that format is not a user-defined string. For more information, see Avoiding Buffer Overruns. If using the secure versions of these functions (either the _s or _p suffixes), a user-supplied format string could trigger an invalid parameter exception if the user-supplied string contains invalid formatting characters.

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Remarks

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