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 ||
           _POSIX_C_SOURCE >= 200112L;
           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  char‐
       acters 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 character type (pointer to a string) containing a multibyte charac‐
              ter sequence beginning in the initial shift state.  Characters from the  array  are
              converted to wide characters (each by a call to the mbrtowc(3) function with a con‐
              version 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 (L'\0').  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 ('\0'), 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
       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  work  correctly
       only  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 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 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.



GNU                                         2014-03-19                                 WPRINTF(3)