1WPRINTF(3)                 Linux Programmer's Manual                WPRINTF(3)
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3
4

NAME

6       wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted
7       wide-character output conversion
8

SYNOPSIS

10       #include <stdio.h>
11       #include <wchar.h>
12
13       int wprintf(const wchar_t *format, ...);
14       int fwprintf(FILE *stream, const wchar_t *format, ...);
15       int swprintf(wchar_t *wcs, size_t maxlen,
16                    const wchar_t *format, ...);
17
18       int vwprintf(const wchar_t *format, va_list args);
19       int vfwprintf(FILE *stream, const wchar_t *format, va_list args);
20       int vswprintf(wchar_t *wcs, size_t maxlen,
21                     const wchar_t *format, va_list args);
22
23   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
24
25       All functions shown above:
26           _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE ||
27           _POSIX_C_SOURCE >= 200112L
28

DESCRIPTION

30       The wprintf() family of functions is the wide-character  equivalent  of
31       the  printf(3)  family  of  functions.  It performs formatted output of
32       wide characters.
33
34       The wprintf() and vwprintf() functions perform wide-character output to
35       stdout.  stdout must not be byte oriented; see fwide(3) for more infor‐
36       mation.
37
38       The fwprintf() and vfwprintf() functions perform wide-character  output
39       to  stream.   stream  must  not be byte oriented; see fwide(3) for more
40       information.
41
42       The swprintf() and vswprintf() functions perform wide-character  output
43       to  an array of wide characters.  The programmer must ensure that there
44       is room for at least maxlen wide characters at wcs.
45
46       These  functions  are  like  the  printf(3),  vprintf(3),   fprintf(3),
47       vfprintf(3), sprintf(3), vsprintf(3) functions except for the following
48       differences:
49
50       ·      The format string is a wide-character string.
51
52       ·      The output consists of wide characters, not bytes.
53
54       ·      swprintf() and vswprintf() take a  maxlen  argument,  sprintf(3)
55              and  vsprintf(3)  do  not.  (snprintf(3) and vsnprintf(3) take a
56              maxlen argument, but these functions do not return -1 upon  buf‐
57              fer overflow on Linux.)
58
59       The treatment of the conversion characters c and s is different:
60
61       c      If  no l modifier is present, the int argument is converted to a
62              wide character by a call  to  the  btowc(3)  function,  and  the
63              resulting  wide  character  is  written.   If  an  l modifier is
64              present, the wint_t (wide character) argument is written.
65
66       s      If no l  modifier  is  present:  the  const char *  argument  is
67              expected  to be a pointer to an array of character type (pointer
68              to a string) containing a multibyte character sequence beginning
69              in  the initial shift state.  Characters from the array are con‐
70              verted to wide characters (each by  a  call  to  the  mbrtowc(3)
71              function  with  a conversion state starting in the initial state
72              before the first byte).  The resulting wide characters are writ‐
73              ten  up to (but not including) the terminating null wide charac‐
74              ter (L'\0').  If a precision is specified, no more wide  charac‐
75              ters  than the number specified are written.  Note that the pre‐
76              cision determines the number of wide characters written, not the
77              number  of  bytes or screen positions.  The array must contain a
78              terminating null byte ('\0'), unless a precision is given and it
79              is so small that the number of converted wide characters reaches
80              it before the end of the array is reached.  If an l modifier  is
81              present:  the  const wchar_t *  argument  is  expected  to  be a
82              pointer to an array of wide characters.   Wide  characters  from
83              the  array  are  written up to (but not including) a terminating
84              null wide character.  If a precision is specified, no more  than
85              the number specified are written.  The array must contain a ter‐
86              minating null wide character, unless a precision is given and it
87              is smaller than or equal to the number of wide characters in the
88              array.
89

RETURN VALUE

91       The functions return the number of wide characters  written,  excluding
92       the terminating null wide character in case of the functions swprintf()
93       and vswprintf().  They return -1 when an error occurs.
94

ATTRIBUTES

96       For  an  explanation  of  the  terms  used   in   this   section,   see
97       attributes(7).
98
99       ┌─────────────────────────┬───────────────┬────────────────┐
100Interface                Attribute     Value          
101       ├─────────────────────────┼───────────────┼────────────────┤
102wprintf(), fwprintf(),   │ Thread safety │ MT-Safe locale │
103swprintf(), vwprintf(),  │               │                │
104vfwprintf(), vswprintf() │               │                │
105       └─────────────────────────┴───────────────┴────────────────┘
106

CONFORMING TO

108       POSIX.1-2001, POSIX.1-2008, C99.
109

NOTES

111       The  behavior  of  wprintf() et al. depends on the LC_CTYPE category of
112       the current locale.
113
114       If the format string contains non-ASCII wide  characters,  the  program
115       will work correctly only if the LC_CTYPE category of the current locale
116       at run time is the same as the LC_CTYPE category of the current  locale
117       at  compile  time.  This is because the wchar_t representation is plat‐
118       form- and locale-dependent.   (The  glibc  represents  wide  characters
119       using  their  Unicode (ISO-10646) code point, but other platforms don't
120       do this.  Also, the use of C99 universal character names  of  the  form
121       \unnnn  does  not solve this problem.)  Therefore, in internationalized
122       programs, the format string should consist  of  ASCII  wide  characters
123       only,  or should be constructed at run time in an internationalized way
124       (e.g., using gettext(3) or iconv(3), followed by mbstowcs(3)).
125

SEE ALSO

127       fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3)
128

COLOPHON

130       This page is part of release 5.02 of the Linux  man-pages  project.   A
131       description  of  the project, information about reporting bugs, and the
132       latest    version    of    this    page,    can     be     found     at
133       https://www.kernel.org/doc/man-pages/.
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137GNU                               2019-03-06                        WPRINTF(3)
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