Re: EPICS app, Db Makefile, rule for python-generated Db file

["Wells, Alex \(DLSLtd,RAL,LSCI\) via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Andrea,

The Makefile modifications are reasonably straightforward. The way I normally do this is as follows:

• Have the Database specified in the "DB" macro; i.e. "DB += myDb.db" (this probably already exists in your IOC's Db/Makefile file)
• Have a file named "myDb.py". This is your epicsdbbuilder script.
• Ensure this file outputs its results to "sys.argv[1]", for reasons explained below
• Add this rule to the Makefile, below that line. Note the "python" line should be indented with a tab:
  %.db: ../%.py
      python $< $@

After this, running "make" should work as expected and you should see "myDb.db" appear in the built top level "db" folder.

To explain the Makefile magic:

• %.db expands to the name of the database file the EPICS build system is currently trying to build
• ../%.py will cause EPICS to target the Python file of the same name as the database file
• python $< $@ will execute "python", passing "$<" (the file path to the Python script) and "$@", the full file path to the database being created. This is why you need to output the database contents to "sys.argv[1]".

Hope that helps!

Alex Wells

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Andrea Celentano via Tech-talk <tech-talk at aps.anl.gov>
Sent: Friday, May 2, 2025 10:54 AM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: EPICS app, Db Makefile, rule for python-generated Db file

 

Dear colleagues,

when developing the EPICS apps that I need, typically I use python scripts to generate Db files, using “epicsdbbuilder” tool (https://github.com/DiamondLightSource/epicsdbbuilder).

At this moment, my development flow is as follows. I create the python file to build the database file inside the “Db” folder, then I manually execute it, and then I run make.

Indeed, in the default Makefile obtained from “makeBaseApp.pl -t ioc”, I see that the last lines read:

#----------------------------------------

#  ADD RULES AFTER THIS LINE

This means that I can, in principle, add a rule so that the python script is executed automatically. However, I am not familiar enough with EPICS compilation system (and in general with Makefile) to write this rule. May I ask you for suggestions?

Thanks,

Bests,

Andrea Celentano

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