MBLEN(3) Linux Programmer's Manual MBLEN(3)
mblen - determine number of bytes in next multibyte character
int mblen(const char *s, size_t n);
If s is not NULL, the mblen() function inspects at most n bytes of the
multibyte string starting at s and extracts the next complete 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 consumed 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 NULL, 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 state-
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.
For an explanation of the terms used in this section, see
|Interface | Attribute | Value |
|mblen() | Thread safety | MT-Unsafe race |
POSIX.1-2001, POSIX.1-2008, C99.
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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GNU 2015-08-08 MBLEN(3)