By defult the applaction use the JSON file (config.json) if these arguments (-r -u -p) are not used, The file should be in the same direcotry with the application.
This method can only update a single domain.
./gddns -r example.com -u Username -p Password
or
#This method uses the config.json to update multiple domains.
./gddns
For other options see the help menu using -h or --help argument.
This is a the template of the JSON file.