DU(1) General Commands Manual DU(1)
du - summarize disk usage
du [ -s ] [ -a ] [ name ... ]
Du gives the number of blocks contained in all files and (recursively)
directories within each specified directory or file name. If name is
missing, `.' is used.
The optional argument -s causes only the grand total to be given. The
optional argument -a causes an entry to be generated for each file.
Absence of either causes an entry to be generated for each directory
A file which has two links to it is only counted once.
Non-directories given as arguments (not under -a option) are not
If there are too many distinct linked files, du counts the excess files