问题
Is it possible using standard C++ in Linux to get informed when a specified date/time is reached by the system time (assuming my process is up of course)?
I could just set a timer to the time I need to wait, but what happens if the user changes the system time? Can I get informed by the system that the user changed the system time to reset my timers?
回答1:
The Linux kernel has such system calls, although, they are not integrated into the libc API. You can create a timer, get a file descriptor for it from the kernel, and do a select or epoll call on the descriptor to be notified when the timer fires.
The man page for it: http://www.kernel.org/doc/man-pages/online/pages/man2/timerfd_create.2.html
回答2:
Sure, just write code to do exactly what you want. For example: You could keep a list of all such timers, the date/time they're supposed to be fired, and what code should be executed when they occur. Then every so often you could check the time to see if it's past the time any of your timers should fire. If so, fire them, remove them from the list, and go on about your business.
回答3:
See the documentation for 'at' command (man at)
For example, at could send you an email at a given time, like 2:35 PM.
at 14:35
warning: commands will be executed using /bin/sh
at> mail -s "It is 2:35 PM" dbadmin < /dev/null
at><EOT> # After CTRL/D pressed.
job 9 at Tue May 8 14:35:00 2012
回答4:
You can calculate the time from program start to the event, and call
sleep (difftime-1);
Then you could control if the time was reset, but this way you would only be able to correct the time to the future - if the time was set back, you would have skipped the event.
来源：https://stackoverflow.com/questions/10496531/is-it-possible-in-c-c-in-linux-to-get-informed-when-a-specified-date-time-is-r