mblen - get number of bytes consisting a multibyte character
Standard C Library (libc, -lc)
mblen(const char *s, size_t n);
The mblen() function usually determines the number of bytes consisting in
a multibyte character pointed by s and return it. This function shall
only examine max n bytes of the array beginning from s.
In state-dependent encodings, s may point the special sequence bytes to
change the shift-state. Although such sequence bytes corresponds to no
individual wide-character code, the mblen() changes the own state by them
and treats them as if they are a part of the subsequence multibyte character.
Unlike mbrlen(3), the first n bytes pointed by s need to form an entire
multibyte character. Otherwise, this function causes an error.
mblen() is equivalent to the following call, except the internal state of
the mbtowc(3) function is not affected:
mbtowc(NULL, s, n);
Calling any other functions in the Standard C Library (libc, -lc) never
change the internal state of the mblen(), except for calling setlocale(3)
with changing LC_CTYPE category of the current locale. Such setlocale(3)
call causes the internal state of this function to be indeterminate.
The behaviour of the mblen() is affected by LC_CTYPE category of the current
There are special cases:
s == NULL The mblen() initializes its own internal state to an initial
state, and determines whether the current encoding is statedependent.
This function returns 0 if the encoding is stateindependent,
n == 0 In this case, the first n bytes of the array pointed by s
never form a complete character. Thus, the mblen() always
In the usual cases, the mblen() returns:
0 s points a null byte ('\0').
positive The value returned is a number of bytes for the valid multibyte
character pointed by s. There is no cases that this
value is greater than n or the value of MB_CUR_MAX macro.
-1 s points an invalid or incomplete multibyte character. The
mblen() also sets errno to indicate the error.
In the case that s is equal to NULL, the mblen() returns:
0 The current encoding is state-independent.
non-zero The current encoding is state-dependent.
The mblen() may causes an error in the following case:
[EILSEQ] s points an invalid or incomplete multibyte character.
mbrlen(3), mbtowc(3), setlocale(3)
The mblen() function conforms to ANSI X3.159-1989 (``ANSI C'').
BSD February 3, 2002 BSD
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