0                  Indicates an error. When the specified name
                       value:

                       o  Is invalid, errno is set to EINVAL.

                       o  Does not have a system-defined value, errno
                          is not set.

    n                  The size of the buffer needed to hold the
                       value.

                       o  When the value of the name argument is
                          system-defined, confstr returns the size of
                          the buffer needed to hold the entire value.
                          If this return value is greater than the
                          len value, the string returned as the buf
                          value is truncated.

                       o  When the value of the len argument is set
                          to 0 or the buf value is NULL, confstr
                          returns the size of the buffer needed to
                          hold the entire system-defined value. The
                          string value is not copied.