BTW, you can monitor file deletion using the inotify syscall. You can register the inotify fd into your epoll and wait for EPOLLIN.
Several months ago, Ahmad Ghani and I used inotify to monitor changes on a credential file in the gwproxy project.
Check this out:
https://github.com/GNUWeeb/gwproxy/blob/60c6c822cf8ab14d80800776435417238ea371b0/src/gwproxy/gwproxy.c#L640-L641
But in this case, I think you should use IN_DELETE_SELF instead of IN_DELETE.
See: man 7 inotify
https://man7.org/linux/man-pages/man7/inotify.7.html