mbrtowc(3)

1mbrtowc(3)                 Library Functions Manual                 mbrtowc(3)
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NAME

6       mbrtowc - convert a multibyte sequence to a wide character
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <wchar.h>
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14       size_t mbrtowc(wchar_t *restrict pwc, const char s[restrict .n],
15                      size_t n, mbstate_t *restrict ps);
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DESCRIPTION

18       The  main  case  for this function is when s is not NULL and pwc is not
19       NULL.  In this case, the mbrtowc() function inspects at most n bytes of
20       the  multibyte  string starting at s, extracts the next complete multi‐
21       byte character, converts it to a wide character and stores it at  *pwc.
22       It updates the shift state *ps.  If the converted wide character is not
23       L'\0' (the null wide character), it returns the number  of  bytes  that
24       were consumed from s.  If the converted wide character is L'\0', it re‐
25       sets the shift state *ps to the initial state and returns 0.
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27       If the n bytes starting at s do not contain a complete multibyte  char‐
28       acter,  mbrtowc()  returns  (size_t) -2.   This can happen even if n >=
29       MB_CUR_MAX, if the multibyte string contains redundant shift sequences.
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31       If the multibyte string starting at s contains an invalid multibyte se‐
32       quence   before   the   next   complete  character,  mbrtowc()  returns
33       (size_t) -1 and sets errno to EILSEQ.  In this case, the effects on *ps
34       are undefined.
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36       A  different case is when s is not NULL but pwc is NULL.  In this case,
37       the mbrtowc() function behaves as above, except that it does not  store
38       the converted wide character in memory.
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40       A  third  case is when s is NULL.  In this case, pwc and n are ignored.
41       If the conversion state represented by *ps denotes an incomplete multi‐
42       byte  character conversion, the mbrtowc() function returns (size_t) -1,
43       sets errno to EILSEQ, and leaves *ps in an undefined state.  Otherwise,
44       the mbrtowc() function puts *ps in the initial state and returns 0.
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46       In  all  of  the  above  cases, if ps is NULL, a static anonymous state
47       known only to the mbrtowc() function is used instead.   Otherwise,  *ps
48       must  be  a  valid mbstate_t object.  An mbstate_t object a can be ini‐
49       tialized to the initial state by zeroing it, for example using
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51           memset(&a, 0, sizeof(a));
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RETURN VALUE

54       The mbrtowc() function returns the number  of  bytes  parsed  from  the
55       multibyte  sequence  starting  at  s, if a non-L'\0' wide character was
56       recognized.  It returns 0, if a L'\0' wide  character  was  recognized.
57       It  returns  (size_t) -1 and sets errno to EILSEQ, if an invalid multi‐
58       byte sequence was encountered.  It returns (size_t) -2 if  it  couldn't
59       parse  a  complete  multibyte  character,  meaning that n should be in‐
60       creased.
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ATTRIBUTES

63       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
64       tributes(7).
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66       ┌─────────────────────────┬───────────────┬────────────────────────────┐
67       │Interface                │ Attribute     │ Value                      │
68       ├─────────────────────────┼───────────────┼────────────────────────────┤
69       │mbrtowc()                │ Thread safety │ MT-Unsafe race:mbrtowc/!ps │
70       └─────────────────────────┴───────────────┴────────────────────────────┘
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STANDARDS

73       C11, POSIX.1-2008.
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HISTORY

76       POSIX.1-2001, C99.
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NOTES

79       The  behavior of mbrtowc() depends on the LC_CTYPE category of the cur‐
80       rent locale.
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