You can run `caffeinate` for a pre-determined amount of time to **prevent sleeping for a specified block of time**, say for 4 hours while you download something, and then run it in the background by adding & to it: ```bash caffeinate -t 14400 & ``` To stop, run ‘kill’ and the process id: ```bash kill 77181 // or whatever the ID is ``` You can also run: ```bash killall caffeinate ``` see: [Disable Sleep on a Mac from the Command Line with caffeinate](http://osxdaily.com/2012/08/03/disable-sleep-mac-caffeinate-command/)