mbtowc(3) Library Functions Manual mbtowc(3)
NAME
mbtowc - convert a multibyte sequence to a wide character
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <stdlib.h>
int mbtowc(wchar_t *restrict pwc, const char s[restrict .n], size_t n);
DESCRIPTION
The main case for this function is when s is not NULL and pwc is not
NULL. In this case, the mbtowc() function inspects at most n bytes of
the multibyte string starting at s, extracts the next complete multi-
byte character, converts it to a wide character and stores it at *pwc.
It updates an internal shift state known only to the mbtowc() function.
If s does not point to a null byte ('\0'), it returns the number of
bytes that were consumed from s, otherwise it returns 0.
If the n bytes starting at s do not contain a complete multibyte char-
acter, or if they contain an invalid multibyte sequence, mbtowc() re-
turns -1. This can happen even if n >= MB_CUR_MAX, if the multibyte
string contains redundant shift sequences.
A different case is when s is not NULL but pwc is NULL. In this case,
the mbtowc() function behaves as above, except that it does not store
the converted wide character in memory.
A third case is when s is NULL. In this case, pwc and n are ignored.
The mbtowc() function resets the shift state, only known to this func-
tion, to the initial state, and returns nonzero if the encoding has
nontrivial shift state, or zero if the encoding is stateless.
RETURN VALUE
If s is not NULL, the mbtowc() function returns the number of consumed
bytes starting at s, or 0 if s points to a null byte, or -1 upon fail-
ure.
If s is NULL, the mbtowc() function returns nonzero if the encoding has
nontrivial shift state, or zero if the encoding is stateless.
ATTRIBUTES
For an explanation of the terms used in this section, see attrib-
utes(7).
┌────────────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├────────────────────────────────────┼───────────────┼────────────────┤
│ mbtowc() │ Thread safety │ MT-Unsafe race │
└────────────────────────────────────┴───────────────┴────────────────┘
VERSIONS
This function is not multithread safe. The function mbrtowc(3) pro-
vides a better interface to the same functionality.
STANDARDS
C11, POSIX.1-2008.
HISTORY
POSIX.1-2001, C99.
NOTES
The behavior of mbtowc() depends on the LC_CTYPE category of the cur-
rent locale.
SEE ALSO
MB_CUR_MAX(3), mblen(3), mbrtowc(3), mbstowcs(3), wcstombs(3), wc-
tomb(3)
Linux man-pages 6.7 2023-10-31 mbtowc(3)
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