SilcUInt16
    silc_client_get_clients_whois(SilcClient client,
                                  SilcClientConnection conn,
                                  const char *nickname,
                                  const char *server,
                                  SilcBuffer attributes,
                                  SilcGetClientCallback completion,
                                  void *context);

    Finds client entry or entries by the `nickname' and `server'. The
    completion callback will be called when the client entries has been
    found.  After the server returns the client information it is cached
    and can be accesses locally at a later time.  The resolving is done
    with WHOIS command.  The `server' may be NULL.  The server
    associated with the nickname may be in the `nickname' (nick@server).
    The `nickname' may also be a formatted nickname in which case the
    formatting is ignored and the base nickname is used.  If the nickname
    is formatted it must be formatted as defined in SilcClientParams.
    Returns 0 on error and the command identifier used with the command
    otherwise.

    If the `attributes' is non-NULL then the buffer includes Requested
    Attributes which can be used to fetch very detailed information
    about the user. If it is NULL then only normal WHOIS query is
    made (for more information about attributes see SilcAttribute).
    Caller may create the `attributes' with silc_client_attributes_request
    function.

    The resolving is done with WHOIS command.  For this reason this
    command may take a long time because it resolves detailed user
    information.