How to correctly read the control port when Tor is started with `--ControlPort auto --ControlPortWriteToFile <TEMPORARY_PATH>`?

Summary

It is possible to start Tor with the following arguments (or parameters in Tor's config file):

--ControlPort auto --ControlPortWriteToFile <TEMPORARY_FILE_PATH>>

So Tor writes to <TEMPORARY_FILE_PATH> file the following:

PORT=127.0.0.1:58771

and you just read it in your program. This sounds obvious but if I'm not missing something it is not.

So I think the following steps are necessary to read the correct port number:

1. Make sure that <TEMPORARY_FILE_PATH> does not exist [to eliminate risk that you read some old value].
2. Start Tor process with the arguments
3. Wait until <TEMPORARY_FILE_PATH> file exists [the file may exist but its content may not be flushed just yet now]
4. Repeat
   • Open <TEMPORARY_FILE_PATH> file for reading and read a single line (ending with \n)
   • When the line starts with PORT=, you can parse the port -> success & break from loop.

I'm aware that you can start Tor and just wait few hunder milliseconds, read the file and you'll get most likely the correct port number. However, I want to read always the correct port number.

My question is: What is the recommended (and correct) procedure to read the control port number?