The strndup function duplicates a specific number of bytes from a
    string. The strndup function is equivalent to the strdup function,
    duplicating the provided string in a new block of memory allocated as
    if by using malloc, with the exception that strndup copies at most
    size plus one bytes into the newly allocated memory, terminating the
    new string with a NUL character.

    If the length of s is larger than size, only size bytes will be
    duplicated. If size is larger than the length of s, all bytes in s
    will be copied into the new memory buffer, including the terminating
    NUL character. The newly created string will always be properly
    terminated.