wprintf

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
       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 5.04 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)