head and tail in Linux CLI - Step-by-Step Execution

Concept Flow - head and tail

Start

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Input File

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head: Read first N lines

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Output first N lines

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tail: Read last N lines

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Output last N lines

The commands read a file and output either the first or last N lines, showing the start or end of the file.

Execution Sample

Linux CLI

head -n 3 sample.txt

tail -n 2 sample.txt

Shows the first 3 lines and last 2 lines of the file 'sample.txt'.

Execution Table

Step	Command	Action	Output Lines	Output Content
1	head -n 3 sample.txt	Reads first 3 lines	3	Line1\nLine2\nLine3
2	tail -n 2 sample.txt	Reads last 2 lines	2	Line4\nLine5
3	head -n 3 sample.txt	If file has fewer than 3 lines, outputs all lines	2	Line1\nLine2
4	tail -n 2 sample.txt	If file has fewer than 2 lines, outputs all lines	1	Line1
5	head -n 0 sample.txt	Reads zero lines, outputs nothing	0
6	tail -n 0 sample.txt	Reads zero lines, outputs nothing	0

💡 Commands stop after reading requested number of lines or entire file if fewer lines exist.

Variable Tracker

Variable	Start	After head -n 3	After tail -n 2	After head -n 0	After tail -n 0
Output Lines	N/A	3 lines	2 lines	0 lines	0 lines
Output Content	N/A	Line1\nLine2\nLine3	Line4\nLine5

Key Moments - 3 Insights

Why does head output fewer lines if the file has less than N lines?

Because head reads up to N lines but stops if the file ends earlier, as shown in execution_table row 3.

What happens if you ask tail or head to output zero lines?

They output nothing, no lines are printed, as shown in execution_table rows 5 and 6.

Does tail read the whole file to get the last lines?

Yes, tail reads from the end to output the last N lines, as shown in execution_table row 2.

Visual Quiz - 3 Questions

Look at the execution_table, how many lines does 'head -n 3 sample.txt' output at step 1?

A 2 lines

B 3 lines

C 5 lines

D 0 lines

💡 Hint

Check the 'Output Lines' column in execution_table row 1.

At which step does the command output zero lines?

A Step 5

B Step 2

C Step 1

D Step 3

💡 Hint

Look for '0' in the 'Output Lines' column in execution_table.

If the file has only 2 lines, what will 'head -n 3' output according to the table?

A 0 lines

B 3 lines

C 2 lines

D No output

💡 Hint

See execution_table row 3 about fewer lines than requested.

Concept Snapshot

head and tail commands:
head -n N filename: outputs first N lines
tail -n N filename: outputs last N lines
If file has fewer lines, outputs all lines
-n 0 outputs nothing
Useful to preview start or end of files

Full Transcript

The head and tail commands in Linux let you see the start or end of a file. Head reads the first N lines, tail reads the last N lines. If the file has fewer lines than requested, they output all lines. Asking for zero lines outputs nothing. This helps quickly check file contents without opening the whole file.