mblen - get number of bytes in a character
#include <stdlib.h> int mblen(const char *s, size_t n);
If s is not a null pointer, mblen() determines the number of bytes constituting the character pointed to by s. It is equivalent to:
mbtowc((wchar_t *)0,s, n);
A call with s as a null pointer causes this function to return 0. The behavior of this function is affected by the LC_CTYPE category of the current locale.
If s is a null pointer, mblen() returns 0. It s is not a null pointer, mblen() returns 0 (if s points to the null byte), the number of bytes that constitute the character (if the next n or fewer bytes form a valid character), or −1 (if they do not form a valid character) and may set errno to indicate the error. In no case will the value returned be greater than n or the value of the MB_CUR_MAX macro.
The mblen() function may fail if:
Invalid character sequence is detected.
See attributes(7) for descriptions of the following attributes: