You can use it to log to a defined file in userspace. You don’t need to “reattach” to the process because all of the output goes through this util. Use signal handling to control the process.

No. https://www.man7.org/linux/man-pages/man1/logger.1.html

You’re right. A data ase would be absolutely stupid. Use a log shipping library instead.

Also, don’t A/B me.

But what’s in this file?

If you’re just shuffling data around, use a database.

This is a very confusing question. What is the concern about this file, and what do you mean about “reattach”? Is it a long running process? Why would locking thw file, or working in memory of tmp not work? Why is screen not an option?