Arguments

Returns

The value of a point in the DataHub instance. If the point is unavailable then nil is returned. For read_existing_point, if the point does not exist than nil is returned. For read_point, if the point does not exist then the point is created and a default value is returned.

Description

These functions makes a call to the DataHub instance to retrieve the point whose name is the same as the symbol. If the point does not exist in the DataHub instance, read_existing_point returns nil and does not create the point. read_point will create a point in the DataHub instance if necessary, whose value and confidence are both zero. If the point name is pre-qualified with a domain name and a colon (:), this function will search that domain's data rather than the DataHub instance for the default domain.

Example

This example uses data points entered in the write_point reference entry example.

Gamma> init_ipc("reader","rq");
t
Gamma> read_point(#my);
600
Gamma> read_point(#dog);
130
Gamma> read_point(#has);
140
Gamma> read_point(#fleas);
150
Gamma> read_existing_point(#cat);
nil
Gamma> read_point(#cat);
0
Gamma> 
		

See Also

register_point, write_point