1WPRINTF(3) Linux Programmer's Manual WPRINTF(3)
2
6 wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - formatted
7 wide character output conversion
8
10 #include <stdio.h>
11 #include <wchar.h>
12 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 #include <stdarg.h>
19 int vwprintf(const wchar_t *format, va_list args);
21 int vfwprintf(FILE *stream, const wchar_t *format, va_list args);
22 int vswprintf(wchar_t *wcs, size_t maxlen,
23 const wchar_t *format, va_list args);
24
26 The wprintf() family of functions is the wide-character equivalent of
27 the printf() family of functions. It performs formatted output of wide
28 characters.
29 The wprintf() and vwprintf() functions perform wide character output to
31 stdout. stdout must not be byte oriented; see function fwide() for
32 more information.
33 The fwprintf() and vfwprintf() functions perform wide character output
35 to stream. stream must not be byte oriented; see function fwide() for
36 more information.
37 The swprintf() and vswprintf() functions perform wide character output
39 to an array of wide characters. The programmer must ensure that there
40 is room for at least maxlen wide characters at wcs.
41 These functions are like the printf(), vprintf(), fprintf(),
43 vfprintf(), sprintf(), vsprintf() functions except for the following
44 differences:
45 · The format string is a wide character string.
47 · The output consists of wide characters, not bytes.
49 · swprintf() and vswprintf() take a maxlen argument, sprintf() and
51 vsprintf() do not. (snprintf() and vsnprintf() take a maxlen
52 argument, but these functions do not return -1 upon buffer over‐
53 flow on Linux.)
54 The treatment of the conversion characters c and s is different:
56 c If no l modifier is present, the int argument is converted to a
58 wide character by a call to the btowc() function, and the
59 resulting wide character is written. If an l modifier is
60 present, the wint_t (wide character) argument is written.
61 s If no l modifier is present: The ``const char *'' argument is
63 expected to be a pointer to an array of character type (pointer
64 to a string) containing a multibyte character sequence beginning
65 in the initial shift state. Characters from the array are con‐
66 verted to wide characters (each by a call to the mbrtowc() func‐
67 tion with a conversion state starting in the initial state
68 before the first byte). The resulting wide characters are writ‐
69 ten up to (but not including) the terminating null wide charac‐
70 ter. If a precision is specified, no more wide characters than
71 the number specified are written. Note that the precision
72 determines the number of wide characters written, not the number
73 of bytes or screen positions. The array must contain a termi‐
74 nating null byte, unless a precision is given and it is so small
75 that the number of converted wide characters reaches it before
76 the end of the array is reached. If an l modifier is present:
77 The ``const wchar_t *'' argument is expected to be a pointer to
78 an array of wide characters. Wide characters from the array are
79 written up to (but not including) a terminating null wide char‐
80 acter. If a precision is specified, no more than the number
81 specified are written. The array must contain a terminating null
82 wide character, unless a precision is given and it is smaller
83 than or equal to the number of wide characters in the array.
84
86 The functions return the number of wide characters written, excluding
87 the terminating null wide character in case of the functions swprintf()
88 and vswprintf(). They return -1 when an error occurs.
89
91 C99.
92
94 fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3), wscanf(3)
95
97 The behaviour of wprintf() et al. depends on the LC_CTYPE category of
98 the current locale.
99 If the format string contains non-ASCII wide characters, the program
101 will only work correctly if the LC_CTYPE category of the current locale
102 at run time is the same as the LC_CTYPE category of the current locale
103 at compile time. This is because the wchar_t representation is platform
104 and locale dependent. (The GNU libc represents wide characters using
105 their Unicode (ISO-10646) code point, but other platforms don't do
106 this. Also, the use of C99 universal character names of the form
107 \unnnn does not solve this problem.) Therefore, in internationalized
108 programs, the format string should consist of ASCII wide characters
109 only, or should be constructed at run time in an internationalized way
110 (e.g. using gettext() or iconv(), followed by mbstowcs()).
111GNU 1999-11-20 WPRINTF(3)