Is it safe to empty both tmp folders? There's a few hundred MB of files that I'd like to get rid of if possible. My hard drive is smaller than what most people have these days, so I like to do a little "house cleaning" now & then....
It usually is, at least if you reboot immediately afterwards. But typically you'll have a lot more than two tmp folders.
~/tmp, /root/tmp and /var/tmp may or may not be symlinks to /tmp, and if they are, they'd be emptied automatically when you empty /tmp. The same goes for temporary directories that are links to subdirectories under /tmp.
But some programs (e.g. e-mail clients) create tmp folders galore. Is it safe to empty them? The program that created them will usually empty them when they aren't needed anymore, so be careful.
If you have lots of RAM, consider moving /tmp to RAM, and it will be empty every time you reboot.