Re: "Inject" code into IOC startup files?

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

Hi Eddy,

The epics-modules/std repository contains an iocsh command "doAfterIocInit".

https://github.com/epics-modules/std/blob/master/stdApp/src/delayCmd.cpp

We use this a lot when we have a single iocsh file where some commands need to be executed before iocInit, and some after iocInit.

For example this file:

https://github.com/CARS-UChicago/GSECARS-EPICS/blob/master/iocBoot/ioc13idc_linux/XPS.cmd

And this one:

https://github.com/CARS-UChicago/GSECARS-EPICS/blob/master/iocBoot/ioc13idd_linux/MeasComp.cmd

Mark

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From: Tech-talk on behalf of Blomley, Edmund (IBPT) via Tech-talk
Sent: Thursday, June 26, 2025 4:27 AM
To: EPICS Tech Talk
Subject: "Inject" code into IOC startup files?

Dear all,

Most of our IOCs use the (current?) "default" IOC structure created by the `makeBaseApp.pl` script. 

Now there are several scenarios where we currently add the same line of code or same „functionality" to each start up file "by convention“. (For new IOCs we have some scripts adjusting the results of `makeBaseApp.pl` from the beginning).

One example: we export the list of PVs after IOC init. Because we use a custom ENV variables set by our systemd script for each IOC, this line is 100% identical for each IOC and looks something like that:

cd ${TOP}/iocBoot/${IOC}
iocInit

# Write list of records.
dbl > "${EPICS_AUTOPVLIST_IOC_FILE}"

The second scenario is to do some things _before_ IOC init: For example load the iocStats records.

Adding these lines of code once is one thing… But for example, now I would like to add recCaster to each startup file… if that is done, we might also can get rid of the dbl export…

So the question: Is there a way to define some generic „hook-in“ behavior which allows to „add code“ _before_ AND _after_ IOC init, where the actual code is managed outside of the IOC structure and could be used across multiple IOCs? Also due to our orchestration and systemd files, we can do some „customization“ during IOC deployment if necessary.

Our current „brain-storming“ idea is maybe through a module, we could add an IOC shell function that allows registering files for later execution. But before we start working on that… other ideas? Is there already a built-in option? Have other labs already created some custom code to allow for something like that?

Cheers

Eddy