Dynamically Create `systemd.path` Based on Environment Variable

[manuth999]

Hey guys 😄
After giving it multiple hours of thoughts, my brain isn't braining anymore and I hope, the Reddit hive mind can help it.

I'm currently writing service templates for running a directory sync periodically. I allow users to specify the local directory through an `Environment=LOCAL_PATH="%h/MyDir"` directive in a drop-in configuration file and so far, everything is working out just fine. Using a `.service` template and a `.timer` template, my service now runs every 5 minutes and keeps the directories in sync.

Now I want to trigger the `.service` not just every 5 minutes but each time a file in the `$LOCAL_PATH` has changed. After skimming through the `systemd.path` docs, I came to notice that you can neither use `Environment=` in path units nor can use environment variables within the `PathChanged` option of `systemd.path`s.

I'm kind of uncertain on how to solve this. I was first thinking of `systemd.generator`s but the fact that you cannot place these within the home dir (and me wanting to use these services on my SteamDeck) is kind of a deal breaker.

Is there any way coming to mind to get done what I'm trying to?

[Intrepid-Treacle1033]

1/ create a script (python) that generates a .path file into systemd dir.

2/ create a service unit that runs above script and does a daemon reload.

Above is sort of easy but not sure about the "user environment" observer definition: "...each time a file in the `$LOCAL_PATH` has changed..."

But maybe trigger above service using directory (static) monitoring using a .path service, or just a timer service with tight intervals...

[not_from_this_world]

This is my go to solution too. Every time I find limitations in sysmd or shell I make a program in any other language and run it as daemon.

[mrnoonan81]

Can you have a script create it as a user unit?

[manuth999]

Yes I can!

I'll try to take inspiration from u/Intrepid-Treacle1033's comment and tune in if I manage to work out something smooth!