du - Summarize disk usage
du [ -a ] [ -s ] [ name… ]
Du gives the number of disk blocks contained in all files and (recursively) directories within each directory specified by the name arguments. If no names are given, the current directory is assumed.
The optional argument -s causes only the grand total (for each of the specified names) to be given. The optional argument -a causes an entry for each file. Absence of either causes an entry to be generated for each directory only.
Non-directories given as arguments are not allowed.
This utility reports sizes in 512-byte blocks.
Output redirection is supported only when the -a argument is not given.