1MBRTOWC(3)                 Linux Programmer's Manual                MBRTOWC(3)
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NAME

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

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

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

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

60       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
61       tributes(7).
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63       ┌─────────────────────────┬───────────────┬────────────────────────────┐
64Interface                Attribute     Value                      
65       ├─────────────────────────┼───────────────┼────────────────────────────┤
66mbrtowc()                │ Thread safety │ MT-Unsafe race:mbrtowc/!ps │
67       └─────────────────────────┴───────────────┴────────────────────────────┘
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CONFORMING TO

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

73       The  behavior of mbrtowc() depends on the LC_CTYPE category of the cur‐
74       rent locale.
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SEE ALSO

77       mbsinit(3), mbsrtowcs(3)
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COLOPHON

80       This page is part of release 5.12 of the Linux  man-pages  project.   A
81       description  of  the project, information about reporting bugs, and the
82       latest    version    of    this    page,    can     be     found     at
83       https://www.kernel.org/doc/man-pages/.
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87GNU                               2021-03-22                        MBRTOWC(3)
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