int mblen(const char *s, size_t n);
If s is not a NULL pointer, the mblen() function inspects at most n
bytes of the multibyte string starting at s and extracts the next com-
plete multibyte character. It uses a static anonymous shift state
known only to the mblen() function. If the multibyte character is not
the null wide character, it returns the number of bytes that were con-
sumed from s. If the multibyte character is the null wide character,
it returns 0.
If the n bytes starting at s do not contain a complete multibyte char-
acter, mblen() returns -1. This can happen even if n is greater than
or equal to MB_CUR_MAX, if the multibyte string contains redundant
If the multibyte string starting at s contains an invalid multibyte
sequence before the next complete character, mblen() also returns -1.
If s is a NULL pointer, the mblen() function resets the shift state,
known to only this function, to the initial state, and returns nonzero
if the encoding has nontrivial shift state, or zero if the encoding is
The mblen() function returns the number of bytes parsed from the multi-
byte sequence starting at s, if a non-null wide character was recog-
nized. It returns 0, if a null wide character was recognized. It
returns -1, if an invalid multibyte sequence was encountered or if it
couldn't parse a complete multibyte character.
Multithreading (see pthreads(7))
The mblen() function is not thread-safe.
The behavior of mblen() depends on the LC_CTYPE category of the current
The function mbrlen(3) provides a better interface to the same func-
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