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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, ...);

       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  ori-
       ented; see fwide(3) for more information.

       The fwprintf() and vfwprintf() functions perform wide-character output to stream.  stream must not be byte ori-
       ented; 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 character 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  char-
              acter  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  mbr-
              towc(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 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 num-
              ber 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
       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 com-
       pile time.  This is because the wchar_t representation is platform- and locale-dependent.   (The  glibc  repre-
       sents 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  interna-
       tionalized  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  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2007-07-26                        WPRINTF(3)