I wrote a cron job to do backups over wifi to another computer. It works perfectly when I’m using the machine, but I prefer to schedule it at night when I’m not using it. The first step is to ping the backup server once and fail the whole script if that step fails.
It consistently fails. 
I’ve got Energy Saver set to never sleep (when plugged in).
Does OS X always put the wifi to sleep after a certain time or something? Does it not wake it up for cron jobs? Or maybe it does, but I just need to wait for it to connect?
Update: @bmike asked about my pmset -g log output. I use terminal-notifier to send a notification.
2015-05-13 16:05:23 -0700 Assertions PID 56(powerd) TimedOut InternalPreventDisplaySleep "com.apple.powermanagement.delayDisplayOff" 00:09:22 id:0x100000032b [System: DeclUser IntPrevDisp kDisp]
2015-05-14 00:00:01 -0700 Assertions PID 552(NotificationCen) Created DisplayWake "com.apple.notificationcenter.sleeping-note" 00:00:00 id:0xe00000bc1 [System: DeclUser DispWake kDisp]
2015-05-14 00:00:11 -0700 Assertions PID 552(NotificationCen) Released DisplayWake "com.apple.notificationcenter.sleeping-note" 00:00:10 id:0xe00000bc1 [System: DeclUser kDisp]
