NEVER EVER used sudo rm -rf.
One slight typo will cause your hard drive be completely wiped clean.
One solitary typo.
If you are going to use sudo rm use the -i tag and not the -f tag.
sudo rm -ri followed by what you want to delete
Yes it takes more time, yes it means having to answer 'y' to each file you want to delete. But if your the "followed by what you want to delete" is a typo, you'll have a chance to correct yourself. Ctrl key + C key to cancel out of the deletion process if it starts asking you to delete files you don't want to delete.
If it tells you such and such is a directory, make note of the directory name and cd into it later on by typing
where name is the name of the directory, and then if you want to delete that directory's contents rm -ri again
But never ever use sudo rm -rf
It is dangerous as having a machine that renders everything invisible with a single shot.
If anyone tells you anything to the contrary, don't follow their advice regarding sudo rm.