wprintf(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

WPRINTF(3)              Linux Programmer's Manual             WPRINTF(3)

NAME         top

       wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf -
       formatted wide-character output conversion

SYNOPSIS         top

       #include <stdio.h>
       #include <wchar.h>

       int wprintf(const wchar_t *restrict format, ...);
       int fwprintf(FILE *restrict stream,
                    const wchar_t *restrict format, ...);
       int swprintf(wchar_t *restrict wcs, size_t maxlen,
                    const wchar_t *restrict format, ...);

       int vwprintf(const wchar_t *restrict format, va_list args);
       int vfwprintf(FILE *restrict stream,
                    const wchar_t *restrict format, va_list args);
       int vswprintf(wchar_t *restrict wcs, size_t maxlen,
                    const wchar_t *restrict 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         top

       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         top

       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         top

       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         top

       POSIX.1-2001, POSIX.1-2008, C99.

NOTES         top

       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         top

       fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3)

COLOPHON         top

       This page is part of release 5.12 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                            2021-03-22                     WPRINTF(3)

Pages that refer to this page: fwide(3)printf(3)