I have always worked with memory outputs from several QGIS geoalgorithms within the Processing Toolbox. If it wasn't specified a location when saving the result, the output was stored as a temporary layer in a specified path, which was in general something like:
If the temporary layer wasn't saved before quitting QGIS, it was automatically deleted from the disk.
Using QGIS 2.18, I casually noted that I'm no longer able to find the temporary output layers in the
Temp folder: this behavior appears to only belong to the QGIS geoalgorithms (instead, the temporary outputs from SAGA or GRASS algorithms are still saved in the
Temp folder, as usual).
If I select one output from the QGIS geoalgorithms and go to
General, I see something like this in the
Layer source field:
As you can see, there isn't any reference to a path in my disk, so I can't find the physical position of the output.
System, I have this path for the temporary files:
In the Processing options, instead, I have:
There is something that I don't know on how the temporary output layers are managed since the current version of QGIS? I encountered this issue using QGIS 2.18, but I don't exclude that it could be started from previous versions of the software.