During simulation, while the background thread is running, or after it is finished, you may use the functions ngSpice_CurPlot (19.3.2.7), ngSpice_AllPlots (19.3.2.8), ngSpice_AllVecs (19.3.2.9) to retrieve information about vectors available, and function ngGet_Vec_Info (19.3.2.5) to obtain data from a vector and its corresponding scale vector. The timing of the caller and the simulation progress are independent from each other and not synchronized.

Again some code to demonstrate the callback function usage is referenced below (19.5).