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MBTOWC(3) Linux Programmer's Manual MBTOWC(3)
NAME
mbtowc - convert a multibyte sequence to a wide character
SYNOPSIS
#include <stdlib.h>
int mbtowc(wchar_t *restrict pwc, const char *restrict s, 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 multibyte 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 character, or if they contain an invalid multibyte sequence, mbtowc() returns -1. This can hap‐
pen 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 function, 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 failure.
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 attributes(7).
┌───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼────────────────┤
│mbtowc() │ Thread safety │ MT-Unsafe race │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C99.
NOTES
The behavior of mbtowc() depends on the LC_CTYPE category of the current locale.
This function is not multithread safe. The function mbrtowc(3) provides a better interface to the same functionality.
SEE ALSO
MB_CUR_MAX(3), mblen(3), mbrtowc(3), mbstowcs(3), wcstombs(3), wctomb(3)
GNU 2021-03-22 MBTOWC(3)