The specification for "du" is as specified in the SUS but with the following differences as listed below.
use SIZE-byte blocks
print size in bytes
produce a grand total
dereference PATHs when symbolic link
print sizes in human readable (e.g., 1K 234M 2G)
equivalent to --block-size=1024
count sizes many times if hard linked
dereference all symbolic links
equivalent to --block-size=1048576
This option (as specified in the SUS) is not supported
do not include size of subdirectories
Exclude files that match any pattern in FILE
Exclude files that match PAT
print the total for a directory (or file, with --all) only if it is N or fewer levels below the command line argument; --max-depth=0 is the same as --summarize
output version information and exit