du \*- summarize disk usage
gives the number of blocks contained in all files
and (recursively) directories within each specified directory or
causes only the grand total to
causes an entry to be generated
Absence of either causes an entry to be generated for
A file which has two links to it is only counted once.
given as arguments (not under
file systems do not work correctly
since i-numbers may be repeated while the corresponding
should maintain an i-number list per root directory