du [–a|–s[–krtx] [ pathname …]
du reports the amount of file space used by the files indicated by the given path name. If the path name is a directory, du reports the total amount of file space used by all files in that directory and in each subdirectory in its hierarchy. If you do not specify a path name, du assumes the current directory. Files with multiple links are only counted once. On systems supporting symbolic links, only the disk space used by the symbolic link is counted.
du measures file space in 512-byte units.
du computes file space in units of 512 bytes. The actual disk space used by files and directories may be more, since some systems allocate space in units of some multiple of a sector. On UNIX System V, it is usually two sectors; on UNIX Version 7, it is one sector.
The allocation unit is file system specific.
See Localization for more information.
POSIX.2 User Portability Extension, X/Open Portability Guide, UNIX systems.
The –t option is an extension to the POSIX standard.
df, find, ls