Experimental Physics and
Industrial Control System

> On Apr 15, 2021, at 11:50 AM, Manoussakis, Adamandios via Tech-talk <tech-talk at aps.anl.gov> wrote:
> 
> I did have one more question with regards to the execute command in the action button.  That technically is just calling a cmd line argument that I place there correct ( python example.py )?   Is there any way to trigger this based off a rule or is it only running the execute command when the button is clicked ?  


Do you really need the script to run when someone clicks on a particular button on a particular screen, or do you need the script to run when a control system process variable changes value? 

If you tie this function to a GUI action button, what happens if there are multiple instances of the GUI open (or zero instances)? What if someone wants to write a shell script or a python script to change the PV value without using your GUI? What happens when some new technology comes out and you want to replace your GUI with something else?

It is generally advisable to restrict the GUI to just providing user interface functionality. Control system logic should be implemented in an IOC (or IOC equivalent like a CA or PVAccess server written in python, java or other language). Functionality like data archiving should be implemented in a dedicated data archiving service. 

If you try to build all of this functionality into the GUI, you will find it to be much more difficult to scale up from a demonstration to a stable production system, and generally difficult to maintain.

EPICS is intended to be a highly distributed system, with many clients interacting with many servers. EPICS provides many tools (IOCs, GUI clients, scripting language clients, archivers, alarm servers, trend tools, etc.). Use the best available tool in the EPICS toolkit to implement the functionality, rather than forcing it into the GUI.

-- 
Steven Hartman
hartmansm at ornl.gov

References:

Python Script call from Button press, module not found Manoussakis, Adamandios via Tech-talk

Re: Python Script call from Button press, module not found Kasemir, Kay via Tech-talk

RE: Python Script call from Button press, module not found Manoussakis, Adamandios via Tech-talk

Re: Python Script call from Button press, module not found Kasemir, Kay via Tech-talk

Re: Python Script call from Button press, module not found Manoussakis, Adamandios via Tech-talk

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