Thank you for your answer.
Using Read node and Write node was only a part. It just keeps not working, and It took me hours to figure it out.
There is a screenshot.
I need viewer2 to be connected to RunScript1 (arrow bottom left). Viewer2 also needs to be active viewer. And I need to click on one of RunScript1's file parameter recycle buttons to activate RunScript1 node (arrow up right). Without these steps, RunScript1 won't be triggerend.
Maybe I missed something. Do you know a more intuitive solution without active Viewer node attached directly to RunScript node, and without need to hit recycle button?