问题
I have an application written in C which runs as a daemon and needs to send something through RS232 when system is in shutdown or reboot state, and it needs to distinguish between these two. So my idea is: In my application script /etc/init.d/my_app in "stop" case of my script, I will run /sbin/runlevel command to get current runlevel: 0 - shutdown state 6 - reboot state then I will execute some command to inform my daemon which state is it, daemon will perform communication through rs, and then will exit.
I think it should work, however it may not be the best solution, especially because my app is already running as a daemon, maybe I can receive some signal directly from system/kernel/library or through unix socket or something.
Best regards
Marek
回答1:
I am not sure which signal is send to an application on system shutdown. My best guess is SIGTERM and if the application does not shutdown SIGKILL. So did you try to catch SIGTERM and properly shut down your program? There are a lot of examples on the net how to do that.
For more sophisticated process handling you can send SIGUSR1, SIGUSR2 to your application.
来源：https://stackoverflow.com/questions/19269825/how-do-i-detect-shutdown-reboot-from-linux-app