About c : Daemon-clean-up-itself-when-get-killed

I’m try to create a daemon application by following the example :

Creating a daemon in Linux

In the example, there is no operations about the daemon stop.

Therefore, I’m curious about :

1. How to send stop signal to the daemon ? Or just kill PID directly ?
2. If the daemon only can stop on killed, should the daemon itself do the cleaning up operations on killed ? Just like close file descriptors, saving parameters, etc.

Thanks in advance.

should the daemon itself do the cleaning up operations on killed ? Just like close file descriptors, saving parameters, etc.

Closing file descriptors is pointless — they’ll be automatically closed by the kernel when the process exits.

For “saving parameters”, it depends on what you mean by “parameters”. If you mean the command-line arguments, then no: when the daemon is restarted, it will get a fresh copy of these.