du Command

Purpose:

Summarizes disk usage.

Syntax:

du [ -a | -s ] [ -k ] [ -m ] [ -g ][ -l ] [ -r ] [ -x ] [ -H | -L ][ File ... ]

Description:

The du command displays the number of blocks used for files. If the File
parameter specified is actually a directory, all files within the directory are
reported on. If no File parameter is provided, the du command uses the files in
the current directory.

If the File parameter is a directory, then the number of blocks reported is the
sum of blocks allocated for the files in the directory and the blocks allocated
for the directory itself.

Specifying the -a flag reports the number of blocks in individual files.
Whether the -a flag is used or not, individual files specified by the File
parameter are always listed.

Specifying the -s flag reports the total blocks for all specified files or all
files in a directory.

The block count includes indirect blocks of each file. Block count is
calculated in 512-byte units independent of the cluster size used by the
system. Specifying the -k flag calculates the block count in 1024-byte units.
Notes:

1. Files with multiple links are counted and written for only one entry.
2. Block counts are based only on file size; therefore, unallocated blocks
are not accounted for in the reported block counts.
3. If du cannot obtain the file attributes or cannot read directories, it
reports an error and the exit status of the command is affected.

Flags:

-a Displays disk usage for each file specified, or displays the individual disk
usage for each file in a directory. Contrast this flag with the -s flag.

-g Calculates the block count in GB units rather than the default 512-byte
units. The output values for the disk usage would be in floating point numbers
as value of each unit in bytes is significantly high.

-H If a symbolic link is specified on the command line, the du command shall
count the size of the file or file hierarchy referenced by the link.

-k Calculates the block count in 1024-byte units rather than the default
512-byte units.

-l Allocates blocks evenly among the links for files with multiple links. By
default, a file with two or more links is counted only once.

-L If a symbolic link is specified on the command line or encountered during
the traversal of a file hierarchy, the du command shall count the size of the
file or file hierarchy referenced by the link.

-m Calculates the block count in MB units rather than the default 512-byte
units. The output values for the disk usage would be in floating point numbers
as value of each unit in bytes is significantly high.

-r Reports names of inaccessible files and directories. This is the default.

-s Displays the total disk usage for all specified files, or displays the total
disk usage for all files in a directory. Contrast this flag with the -a flag.

-x When evaluating file sizes, evaluates only those files that reside on the
same device as the file or directory specified by the File parameter. For
example, you may specify a directory that contains files on several devices. In
this case, the -x flag displays block sizes for all files that reside on the
same device as the directory.

If all or any two of the -k, -m and -g flags are specified, the last one
specified takes effect. The output of the disk usage with the flags -m and -g
would be rounded off to the nearest second decimal digit.

Exit Status

This command returns the following exit values:

0 Successful completion.

>0 An error occurred.

Examples:

1. To summarize the disk usage of a directory tree and each of its subtrees,
enter:

du /home/fran

This displays the number of disk blocks in the /home/fran directory and
each of its subdirectories.
2. To summarize the disk usage of a directory tree and each of its subtrees
in 1024-byte blocks, enter:
du -k /home/fran

This displays the number of 1024-byte disk blocks in the /home/fran
directory and each of its subdirectories.
3. To summarize the disk usage of a directory tree and each of its subtrees
in MB blocks, enter:
du -m /home/fran

This displays the number of MB disk blocks rounded off to nearest 2nd
decimal digit in the /home/fran directory and each of its subdirectories.
4. To summarize the disk usage of a directory tree and each of its subtrees
in GB blocks, enter:
du -g /home/fran

This displays the number of GB disk blocks rounded off to nearest 2nd
decimal digit in the /home/fran directory and each of its subdirectories.
5. To display the disk usage of each file, enter:
du -a /home/fran

This displays the number of disk blocks contained in each file and
subdirectory of the /home/fran directory. The number beside a directory is
the disk usage of that directory tree. The number beside a regular file is
the disk usage of that file alone.
6. To display only the total disk usage of a directory tree, enter:
du -s /home/fran

The -s flag instructs the du command to display only the sum total disk
usage of the /home/fran directory and the files it contains. By default,
the du command displays an error message if it cannot read a file or
directory.
7. To display the disk usage of the files and file hierarchies referenced by
all the symbolic links in addition to the normal files found during
traversal of a the /home/fran directory, type:
du -L /home/fran

8. To report the disk usage of the file or file hierarchy referenced by the
symbolic link mylink, type:
du -H mylink