Is there a way to programmatically get the same information that diskutil info / | grep "Free Space" gives you? (For obvious reasons I'd rather have a better way to do this than just parsing the result of that command.)
Currently I'm using statfs; however, it was brought to my attention that the space this reports is not always accurate, because OS X also places temporary files such as Time Machine snapshots on the drive. These files automatically get deleted if space is running out, and the OS does not report the usage of these files. In other words, statfs often gives a lower number of free space than diskutil info or looking at the disk information in Finder.