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swprintf(3)

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:

       •      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  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 attrib‐
       utes(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 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 5.02 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)
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