Estimate disk space usage (POSIX)
du [-a|-s] [-kpqx] [file...]
The du utility prints the amount of file space allocated to the specified files. If you name a directory, all files in that directory are reported; subdirectories are traversed recursively. If a file has multiple links, the space allocated to that file is counted only once.
The space figures are displayed in 512-byte blocks by default. If you want du to print the size in bytes, specify the -p option. The sizes output by du when you specify the -p option are accurate with one exception: the numbers may be slightly higher than expected because they include extent blocks that are part of filesystem overhead associated with the file, but don't contain actual data.
If you specify nondirectories, they aren't listed unless you specify the -a option.
All results are written to the standard output. Errors may result in diagnostic messages to the standard error. Standard input isn't used.
Estimate disk space consumed by the contents of /tmp, in kbytes:
du -k /tmp
Estimate the total space occupied by the contents of the current directory: