du (disk usage by directory) in Linux CLI - Step-by-Step Execution

Concept Flow - du (disk usage by directory)

Start du command

↓

Read directory contents

↓

Calculate size of each file

↓

Sum sizes per directory

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Display sizes

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End

The du command reads directory contents, calculates file sizes, sums them per directory, and displays the disk usage.

Execution Sample

Linux CLI

du -sh /home/user/Documents

Shows the total disk usage of the Documents directory in a human-readable format.

Execution Table

Step	Action	Directory/File	Size Calculated	Output
1	Start du command	/home/user/Documents
2	Read directory contents	/home/user/Documents
3	Calculate size	/home/user/Documents/file1.txt	4K
4	Calculate size	/home/user/Documents/file2.pdf	12M
5	Read directory contents	/home/user/Documents/Subfolder
6	Calculate size	/home/user/Documents/Subfolder/file3.jpg	2M
7	Sum sizes	/home/user/Documents/Subfolder	2M
8	Sum sizes	/home/user/Documents	14M
9	Display total size	/home/user/Documents	14M	14M /home/user/Documents

💡 All files and subdirectories processed, total size displayed.

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 6	After Step 7	After Step 8	Final
Current File/Dir		/home/user/Documents/file1.txt	/home/user/Documents/file2.pdf	/home/user/Documents/Subfolder/file3.jpg	/home/user/Documents/Subfolder	/home/user/Documents
Size Calculated		4K	12M	2M	2M	14M	14M

Key Moments - 2 Insights

Why does du show sizes for subdirectories separately before summing?

du calculates sizes for each file and subdirectory first (see steps 3-6), then sums them up (steps 7-8) to show total usage.

What does the -h option do in du -sh?

The -h option makes sizes human-readable (like 4K, 12M) instead of bytes, making it easier to understand the output (step 9).

Visual Quiz - 3 Questions

Look at the execution table, what size is calculated for /home/user/Documents/file2.pdf at step 4?

A 12M

B 4K

C 2M

D 14M

💡 Hint

Check the 'Size Calculated' column at step 4 in the execution_table.

At which step does du sum the sizes of the Subfolder directory?

A Step 5

B Step 6

C Step 7

D Step 8

💡 Hint

Look for the 'Sum sizes' action related to Subfolder in the execution_table.

If the -h option was removed, how would the output at step 9 change?

A Sizes would be shown in megabytes only

B Sizes would be shown in bytes instead of human-readable units

C Output would include file names only

D Output would be sorted alphabetically

💡 Hint

The -h option controls human-readable size formatting as seen in the execution_sample description.

Concept Snapshot

du command shows disk usage of directories.
Syntax: du [options] [directory]
-h shows sizes in human-readable form.
-s shows total size only.
Reads files, sums sizes, displays result.

Full Transcript

The du command calculates disk usage by reading directory contents, measuring each file's size, summing sizes for subdirectories, and then displaying the total size. Using options like -h makes the output easier to read by showing sizes in KB, MB, etc. The process starts by reading files, calculating sizes step-by-step, summing them, and finally printing the total usage. This helps users understand how much space a directory and its contents occupy on disk.