Storing Persistent Data

Your module must use the read_config_store_data() and read_config_store() functions together with callback functions to store data.

Your module must first register a callback with the snmp_register_callback() function so that data is written to the configuration file when the agent shuts down.

The snmp_register_callback() function is as follows:

int snmp_register_callback(int major, 
                           int minor, 
                           SNMPCallback *new_callback, 
                           void *arg);

You must set major to SNMP_CALLBACK_LIBRARY, set minor to SNMP_CALLBACK_STORE_DATA. When arg is not set to NULL, arg is a void pointer used whenever the new_callback function is exercised.

The prototype to your callback function, the new_callback pointer, is as follows:

int (SNMPCallback) (int majorID, 
                    int minorID, 
                    void *serverarg, 
                    void *clientarg);

See the API documentation for more information about setting up callback registrations with the agent at /usr/sfw/doc/sma_snmp/html/group__callback.html.

The read_config_store_data() function should be used to create the token-value pair that is to be written into the module's configuration file. The read_config_store() function actually does the storing when the registered callbacks are exercised upon agent shutdown.

When your module stores persistent data, you might find that the configuration file is written to the /var/sma_snmp directory. Modified token-value pairs are appended to the file, rather than overwriting the previous token-value pairs in the file. The last values that were defined in the file are the values that are used.