Functionality that run after load/reload of the Asterisk

Colleagues, please tell me the answer to my question.

Is it possible, after loading or rebooting Asterisk, to launch some functionality first of all?

Macro, subroutine, context?

Thanks in advance for your reply,
Ogogon.

Create a call file in the script that starts Asterisk.

An unexpected way! I didn’t even think about something like that! Thank you!
However, there are also weaknesses in this solution.
Call files are created by external functions. They don’t know anything about the timing of Asterisk reboots. It is also not always possible to delete these files - they have some kind of functional meaning.
It may turn out that my starting call file will not be the first, but the twentieth.

But really, during the entire existence of Asterisk, no one has done something like a rc-script?

Ensuring that nothing except things created by the script ran before it completed, might be a bit fiddly, internally.