du command, short for disk usage, is used to estimate file space usage.
The du command can be used to track the files and directories which are consuming excessive amount of space on hard disk drive.

Syntax :

du [OPTION]... [FILE]...
du [OPTION]... --files0-from=F

Examples :

du /home/mandeep/test

Output:

44    /home/mandeep/test/data
2012    /home/mandeep/test/system design
24    /home/mandeep/test/table/sample_table/tree
28    /home/mandeep/test/table/sample_table
32    /home/mandeep/test/table
100104    /home/mandeep/test

Options :

-0, –null : end each output line with NULL
-a, –all : write count of all files, not just directories
–apparent-size : print apparent sizes, rather than disk usage.
-B, –block-size=SIZE : scale sizes to SIZE before printing on console
-c, –total : produce grand total
-d, –max-depth=N : print total for directory only if it is N or fewer levels below command line argument
-h, –human-readable : print sizes in human readable format
-S, -separate-dirs : for directories, don’t include size of subdirectories
-s, –summarize : display only total for each directory
–time : show time of last modification of any file or directory.
–exclude=PATTERN : exclude files that match PATTERN

Command usage examples with options :

1. If we want to print sizes in human readable format(K, M, G), use -h option

   du -h /home/mandeep/test 
   
   Output:
   44K    /home/mandeep/test/data
   2.0M    /home/mandeep/test/system design
   24K    /home/mandeep/test/table/sample_table/tree
   28K    /home/mandeep/test/table/sample_table
   32K    /home/mandeep/test/table
   98M    /home/mandeep/test
   Use -a option for printing all files including directories.
   du -a -h /home/mandeep/test
   Output:
   This is partial output of above command.
   4.0K    /home/mandeep/test/blah1-new
   4.0K    /home/mandeep/test/fbtest.py
   8.0K    /home/mandeep/test/data/4.txt
   4.0K    /home/mandeep/test/data/7.txt
   4.0K    /home/mandeep/test/data/1.txt
   4.0K    /home/mandeep/test/data/3.txt
   4.0K    /home/mandeep/test/data/6.txt
   4.0K    /home/mandeep/test/data/2.txt
   4.0K    /home/mandeep/test/data/8.txt
   8.0K    /home/mandeep/test/data/5.txt
   44K    /home/mandeep/test/data
   4.0K    /home/mandeep/test/notifier.py
   Use -c option to print total size
   du -c -h /home/mandeep/test
   Output:
   44K    /home/mandeep/test/data
   2.0M    /home/mandeep/test/system design
   24K    /home/mandeep/test/table/sample_table/tree
   28K    /home/mandeep/test/table/sample_table
   32K    /home/mandeep/test/table
   98M    /home/mandeep/test
   98M    total
   To print sizes till particular level, use -d option with level no.
   du -d 1 /home/mandeep/test
   Output:
   44    /home/mandeep/test/data
   2012    /home/mandeep/test/system design
   32    /home/mandeep/test/table
   100104    /home/mandeep/test
   Now try with level 2, you will get some extra directories
   du -d 2 /home/mandeep/test
   Output:
   44    /home/mandeep/test/data
   2012    /home/mandeep/test/system design
   28    /home/mandeep/test/table/sample_table
   32    /home/mandeep/test/table
   100104    /home/mandeep/test
   Get summary of file system using -s option
   du -s /home/mandeep/test
   Output:
   100104    /home/mandeep/test
   Get the timestamp of last modified using --time option
   du --time -h /home/mandeep/test
   Output:
   44K    2018-01-14 22:22    /home/mandeep/test/data
   2.0M    2017-12-24 23:06    /home/mandeep/test/system design
   24K    2017-12-30 10:20    /home/mandeep/test/table/sample_table/tree
   28K    2017-12-30 10:20    /home/mandeep/test/table/sample_table
   32K    2017-12-30 10:20    /home/mandeep/test/table
   98M    2018-02-02 17:32    /home/mandeep/test
   

- Mandeep Singh

References :
1) du wikipedia
2) du man entry

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