Getting accurate "disk usage" info in OS X

Yesterday's MDJ notes that, to see the amount of free space on a disk, select Show Info for the volume icon as seen in a Finder window, not a similar volume icon on the desktop. The desktop icons are actually aliases. Aliases in OS X are known, in some cases (including this one), to have inaccurate information as compared to the original. You may also have to logout and log back in before even the correct Show Info window has accurate data (see this TIL article).

The article also states that using the Terminal <du> (disk usage) command is not a great alternative to Show Info: "First, 'du' only measures the disk usage of files to which you have access, so it gives a distorted picture unless you run it with root access. Second, it only measures the disk usage of the current directory..."

Update: Jonathan Bost suggests: "The best way to get info on disk usage is by the terminal command <df>. By default, this lists disk sizes and usage in 512K blocks, but if you have the newest version of df installed , <df -h> will put the output in kilobytes, MB, or GB for easy reading. (I seem to recall installing a package of Unix tools called Filetools that included the updated version of this utility.)"

Update: Rob Pattay notes that the Terminal command <df -k> shows disk usage in 1K blocks (not the 512K default for df itself). This works with no additional install needed.