fwprintf

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 in-
       formation.

       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),  vf-
       printf(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  buf-
              fer 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  re-
              sulting 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  ex-
              pected 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  at-
       tributes(7).

       +-------------------------+---------------+----------------+
       |Interface                | Attribute     | Value          |
       +-------------------------+---------------+----------------+
       |wprintf(), fwprintf(),   | Thread safety | MT-Safe locale |
       |swprintf(), vwprintf(),  |               |                |
       |vfwprintf(), vswprintf() |               |                |
       +-------------------------+---------------+----------------+

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  us-
       ing  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 5.05 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                               2019-03-06                        WPRINTF(3)