mbtowc(3)

1mbtowc(3)                  Library Functions Manual                  mbtowc(3)
2
3
4

NAME

6       mbtowc - convert a multibyte sequence to a wide character
7

LIBRARY

9       Standard C library (libc, -lc)
10

SYNOPSIS

12       #include <stdlib.h>
13
14       int mbtowc(wchar_t *restrict pwc, const char s[restrict .n], size_t n);
15

DESCRIPTION

17       The  main  case  for this function is when s is not NULL and pwc is not
18       NULL.  In this case, the mbtowc() function inspects at most n bytes  of
19       the  multibyte  string starting at s, extracts the next complete multi‐
20       byte character, converts it to a wide character and stores it at  *pwc.
21       It updates an internal shift state known only to the mbtowc() function.
22       If s does not point to a null byte ('\0'), it  returns  the  number  of
23       bytes that were consumed from s, otherwise it returns 0.
24
25       If  the n bytes starting at s do not contain a complete multibyte char‐
26       acter, or if they contain an invalid multibyte sequence,  mbtowc()  re‐
27       turns  -1.   This  can happen even if n >= MB_CUR_MAX, if the multibyte
28       string contains redundant shift sequences.
29
30       A different case is when s is not NULL but pwc is NULL.  In this  case,
31       the  mbtowc()  function behaves as above, except that it does not store
32       the converted wide character in memory.
33
34       A third case is when s is NULL.  In this case, pwc and n  are  ignored.
35       The  mbtowc() function resets the shift state, only known to this func‐
36       tion, to the initial state, and returns nonzero  if  the  encoding  has
37       nontrivial shift state, or zero if the encoding is stateless.
38

RETURN VALUE

40       If  s is not NULL, the mbtowc() function returns the number of consumed
41       bytes starting at s, or 0 if s points to a null byte, or -1 upon  fail‐
42       ure.
43
44       If s is NULL, the mbtowc() function returns nonzero if the encoding has
45       nontrivial shift state, or zero if the encoding is stateless.
46

ATTRIBUTES

48       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
49       tributes(7).
50
51       ┌─────────────────────────────────────┬───────────────┬────────────────┐
52       │Interface                            │ Attribute     │ Value          │
53       ├─────────────────────────────────────┼───────────────┼────────────────┤
54       │mbtowc()                             │ Thread safety │ MT-Unsafe race │
55       └─────────────────────────────────────┴───────────────┴────────────────┘
56

VERSIONS

58       This  function  is  not  multithread  safe.   The  function  mbrtowc(3)
59       provides a better interface to the same functionality.
60

STANDARDS

62       C11, POSIX.1-2008.
63

HISTORY

65       POSIX.1-2001, C99.
66

NOTES

68       The behavior of mbtowc()  depends  on  the  LC_CTYPE  category  of  the
69       current locale.
70