-The exit code will be 0 if nothing has gone wrong. If a validation
-error occurs, the return value is incremented by 1. If a disallowed
-record type is encountered, the return value is incremented by 2.
+The exit code will be 0 if nothing has gone wrong. If any validation
+error occured, the return value is incremented by 1. If a disallowed
+record type was encountered, the return value is incremented by 2.
+If you forgot to pass the required filename arguments (either the
+tinydns-data files or the filter configuration files), then we exit
+immediately with code 4.