ncdu helps displaying disk usage in an easy way, to install:

brew install ncdu

To scan and browse the directory you're currently in, all you need is a simple:

ncdu

If you want to scan a full filesystem, your root filesystem, for example, then you'll want to use "-x":

ncdu -x /

All files read only and in local machine:

sudo ncdu -rx /

-r option is for read only mode, option -x is to stay in the same file system (do not traverse other filesystem mounts)