swprintf(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
   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 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
          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 (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.

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(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
   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 4.09 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/.

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