Determines the number of bytes comprising a multibyte character.
    Format
      #include  <stdlib.h>
      int mblen  (const char *s, size_t n);
1 – Arguments
 s
    A pointer to the multibyte character.
 n
    The maximum number of bytes that comprise the multibyte
    character.
2 – Description
    If the character is n bytes or less, the mblen function returns
    the number of bytes comprising the multibyte character pointed
    to by s. If the character is greater than n bytes, the function
    returns -1 to indicate an error.
    This function is affected by the LC_CTYPE category of the
    program's current locale.
3 – Return Values
    x                  The number of bytes that comprise the
                       multibyte character, if the next n or fewer
                       bytes form a valid character.
    0                  If s is NULL or a pointer to the NULL
                       character.
    -1                 Indicates an error. The function sets errno to
                       EILSEQ - Invalid character detected.