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



NAME
       wprintf,  fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted wide-char-
       acter 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, ...);

       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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       All functions shown above: _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION
       The wprintf() family of functions is the wide-character equivalent of the printf(3)
       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 fwide(3) for more information.

       The fwprintf() and vfwprintf() functions perform wide-character output  to  stream.
       stream must not be byte oriented; see fwide(3) 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 characters at wcs.

       These  functions  are  like  the  printf(3),  vprintf(3),  fprintf(3), vfprintf(3),
       sprintf(3), vsprintf(3) functions except for the following differences:

       ?      The format string is a wide-character string.

       ?      The output consists of wide characters, not bytes.

       ?      swprintf()  and  vswprintf()  take  a  maxlen   argument,   sprintf(3)   and
              vsprintf(3)  do  not.  (snprintf(3) and vsnprintf(3) 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 charac-
              ter  by a call to the btowc(3) 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.  Charac-
              ters from the array are converted to wide characters (each by a call to  the
              mbrtowc(3)  function  with  a conversion state starting in the initial state
              before the first byte).  The resulting 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 characters written,
              not the number of bytes or screen positions.  The array must contain a  ter-
              minating  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 terminat-
       ing null wide character in case of the functions swprintf() and vswprintf().   They
       return -1 when an error occurs.

CONFORMING TO
       C99.

NOTES
       The  behavior  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
       correctly 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  representation  is  platform- and locale-dependent.  (The glibc represents
       wide characters using their Unicode (ISO-10646) code  point,  but  other  platforms
       don't  do  this.  Also, the use of 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(3) or iconv(3),  followed
       by mbstowcs(3)).

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

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



GNU                               2007-07-26                        WPRINTF(3)

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