x                  The number of bytes written to the string
                       pointed to by s, not including the null-
                       terminating character.
    -1                 Indicates an error. The function sets errno to
                       one of the following values:

                       o  EINVAL - A conversion specification is
                          syntactically incorrect.

                       o  E2BIG - Processing the complete format
                          string would produce more than maxsize
                          bytes.