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man:vfwprintf

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

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 infor-
     mation.
     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:
     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(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 character sequence beginning
            in  the initial shift state.  Characters from the array are con-
            verted 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 writ-
            ten  up to (but not including) the terminating null wide charac-
            ter (L'\0').  If a precision is specified, no more wide  charac-
            ters  than the number specified are written.  Note that the pre-
            cision 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 ter-
            minating 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.

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).
     allbox;  lbw24  lb  lb  l l l.  Interface Attribute Value T{ wprintf(),
     fwprintf(),
     swprintf(), vwprintf(),
     vfwprintf(), vswprintf() T}   Thread safety  MT-Safe locale

CONFORMING TO

     POSIX.1-2001, POSIX.1-2008, 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 representation  is  plat-
     form-  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 4.16 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
     https://www.kernel.org/doc/man-pages/.

GNU 2017-09-15 WPRINTF(3)

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