Originální popis anglicky: 
vfwprintf, vswprintf, vwprintf - wide-character formatted output of a stdarg
  argument list
Návod, kniha: POSIX Programmer's Manual
#include <stdarg.h>
 
#include <stdio.h>
 
#include <wchar.h>
 
 
int vfwprintf(FILE *restrict 
 stream, const wchar_t
  *restrict  format,
 
       va_list 
  arg );
 
int vswprintf(wchar_t *restrict 
 ws, size_t
  n,
 
       const wchar_t *restrict 
   format, va_list
  arg);
 
int vwprintf(const wchar_t *restrict 
 format,
  va_list  arg);
 
The 
vfwprintf(), 
vswprintf(), and 
vwprintf() functions
  shall be equivalent to 
fwprintf(), 
swprintf(), and
  
wprintf() respectively, except that instead of being called with a
  variable number of arguments, they are called with an argument list as defined
  by 
<stdarg.h>.
These functions shall not invoke the 
va_end macro. However, as these
  functions do invoke the 
va_arg macro, the value of 
ap after the
  return is unspecified.
Refer to 
fwprintf() .
Refer to 
fwprintf() .
The following sections are informative.
None.
Applications using these functions should call 
va_end(
ap)
  afterwards to clean up.
None.
None.
fwprintf() , the Base Definitions volume of
  IEEE Std 1003.1-2001, 
<stdarg.h>,
  
<stdio.h>, 
<wchar.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
  Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
  Operating System Interface (POSIX), The Open Group Base Specifications Issue
  6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
  Engineers, Inc and The Open Group. In the event of any discrepancy between
  this version and the original IEEE and The Open Group Standard, the original
  IEEE and The Open Group Standard is the referee document. The original
  Standard can be obtained online at http://www.opengroup.org/unix/online.html
  .