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RedHat 9 (Linux i386) - man page for vswprintf (redhat section 3)

WPRINTF(3)			    Linux Programmer's Manual			       WPRINTF(3)

NAME
       wprintf,  fwprintf,  swprintf,  vwprintf,  vfwprintf, vswprintf - formatted wide character
       output conversion

SYNOPSIS
       #include <stdio.h>
       #include <wchar.h>

       int wprintf(const wchar_t *format, ...);
       int fwprintf(FILE *stream, const wchar_t *format, ...);
       int swprintf(wchar_t *wcs, size_t maxlen,
		     const wchar_t *format, ...);

       #include <stdarg.h>

       int vwprintf(const wchar_t *format, va_list args);
       int vfwprintf(FILE *stream, const wchar_t *format, va_list args);
       int vswprintf(wchar_t *wcs, size_t maxlen,
		      const wchar_t *format, va_list args);

DESCRIPTION
       The wprintf family of functions is the wide-character equivalent of the printf  family  of
       functions. It performs formatted output of wide characters.

       The  wprintf  and  vwprintf functions perform wide character output to stdout. stdout must
       not be byte oriented; see function fwide for more information.

       The fwprintf and vfwprintf functions perform wide character output to stream. stream  must
       not be byte oriented; see function fwide for more information.

       The  swprintf  and  vswprintf  functions perform wide character output to an array of wide
       characters.  The programmer must ensure that there is room for at least maxlen wide  char-
       acters at wcs.

       These  functions  are like the printf, vprintf, fprintf, vfprintf, sprintf, vsprintf func-
       tions except for the following differences:

       o      The format string is a wide character string.

       o      The output consists of wide characters, not bytes.

       o      swprintf and vswprintf take  a  maxlen  argument,  sprintf  and  vsprintf  do  not.
	      (snprintf  and  vsnprintf take a maxlen argument, but these functions do not return
	      -1 upon buffer overflow on Linux.)

       The treatment of the conversion characters c and s is different:

       c      If no l modifier is present, the int argument is converted to a wide character by a
	      call  to	the btowc function, and the resulting wide character is written.  If an l
	      modifier is present, the wint_t (wide character) argument is written.

       s      If no l modifier is present: The ``const char *'' argument  is  expected	to  be	a
	      pointer  to an array of character type (pointer to a string) containing a multibyte
	      character sequence beginning in the initial shift state. Characters from the  array
	      are  converted  to  wide	characters (each by a call to the mbrtowc function with a
	      conversion state starting in the initial state before the first byte). The  result-
	      ing wide characters are written up to (but not including) the terminating null wide
	      character. If a precision is specified, no more wide  characters	than  the  number
	      specified are written.  Note that the precision determines the number of wide char-
	      acters written, not the number of bytes or screen positions.  The array  must  con-
	      tain  a  terminating null byte, unless a precision is given and it is so small that
	      the number of converted wide characters reaches it before the end of the	array  is
	      reached.	--  If	an  l  modifier  is  present: The ``const wchar_t *'' argument is
	      expected to be a pointer to an array of wide characters.	Wide characters from  the
	      array are written up to (but not including) a terminating null wide character. If a
	      precision is specified, no more than the number specified are  written.  The  array
	      must  contain a terminating null wide character, unless a precision is given and it
	      is smaller than or equal to the number of wide characters in the array.

RETURN VALUE
       The functions return the number of wide characters written, excluding the terminating null
       wide  character	in  case  of the functions swprintf and vswprintf. They return -1 when an
       error occurs.

CONFORMING TO
       ISO/ANSI C, UNIX98

SEE ALSO
       printf(3), fprintf(3), snprintf(3), fputwc(3), fwide(3), wscanf(3)

NOTES
       The behaviour of wprintf et al. depends on the LC_CTYPE category of the current locale.

       If the format string contains non-ASCII wide characters, the program will only  work  cor-
       rectly  if  the	LC_CTYPE  category  of	the current locale at run time is the same as the
       LC_CTYPE category of the current locale at compile time. This is because the wchar_t  rep-
       resentation  is	platform  and  locale dependent. (The GNU libc represents wide characters
       using their Unicode (ISO-10646) code point, but other platforms don't do this.  Also,  the
       use  of ISO C99 universal character names of the form \unnnn does not solve this problem.)
       Therefore, in internationalized programs, the format string should consist of  ASCII  wide
       characters  only,  or  should be constructed at run time in an internationalized way (e.g.
       using gettext or iconv, followed by mbstowcs).

GNU					    1999-11-20				       WPRINTF(3)


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