head and tail in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to display the first 5 lines of a file named 'log.txt'.

Linux CLI

head -n [1] log.txt

Drag options to blanks, or click blank then click option'

A20

B10

C5

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using -n 10 shows 10 lines instead of 5.

Forgetting the -n option.

The head command with -n 5 shows the first 5 lines of the file.

2fill in blank

medium

Complete the command to display the last 3 lines of a file named 'data.csv'.

Linux CLI

tail -n [1] data.csv

Drag options to blanks, or click blank then click option'

A5

B3

C10

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using -n 5 shows 5 lines instead of 3.

Confusing head with tail.

The tail command with -n 3 shows the last 3 lines of the file.

3fill in blank

hard

Fix the error in the command to show the first 8 lines of 'report.txt'.

Linux CLI

head [1] 8 report.txt

Drag options to blanks, or click blank then click option'

A-n

B-c

C-l

D-f

Attempts:

3 left

💡 Hint

Common Mistakes

Using -c which shows bytes instead of lines.

Using -f which follows the file continuously.

The correct option to specify number of lines in head is -n. The option -c is for bytes, -f is for following the file.

4fill in blank

hard

Fill both blanks to create a command that shows lines 5 to 10 of 'file.txt' using head and tail.

Linux CLI

head -n [1] file.txt | tail -n [2]

Drag options to blanks, or click blank then click option'

A10

B5

C6

D15

Attempts:

3 left

💡 Hint

Common Mistakes

Using head -n 6 instead of 10.

Using tail -n 5 instead of 6.

First, head -n 10 gets the first 10 lines. Then, tail -n 6 gets the last 6 lines of those 10, which are lines 5 to 10.

5fill in blank

hard

Fill all three blanks to create a command that shows lines containing 'error' (case-insensitive) from the last 4 lines of the first 20 lines of 'access.log'.

Linux CLI

head -n [1] access.log | tail -n [2] | grep -i [3]

Drag options to blanks, or click blank then click option'

A20

B4

C"error"

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong numbers for head or tail options.

Forgetting quotes around the grep pattern.

This command first gets the first 20 lines with head -n 20, then the last 4 lines of those with tail -n 4, and finally filters lines containing 'error' (case-insensitive) with grep -i "error".

Practice

1. What does the head command do by default when run on a text file?

easy

A. Counts the number of lines in the file

B. Shows the last 10 lines of the file

C. Deletes the first 10 lines of the file

D. Shows the first 10 lines of the file

Solution

1. Step 1: Understand the default behavior of head

   The head command shows the start of a file, by default 10 lines.

2. Step 2: Compare with other options

   tail shows the end, but head shows the beginning lines.

3. Final Answer:

   Shows the first 10 lines of the file -> Option D

4. Quick Check:

   head = first 10 lines [OK]

Hint: Remember: head = start, tail = end of file [OK]

Common Mistakes:

• Confusing head with tail
• Thinking head deletes lines
• Assuming head counts lines

2. Which of the following is the correct syntax to display the last 5 lines of a file named log.txt?

easy

A. tail -n 5 log.txt

B. head -n 5 log.txt

C. tail 5 log.txt

D. head 5 log.txt

Solution

1. Step 1: Identify the command to show last lines

   tail shows the end of a file, so it is used to show last lines.

2. Step 2: Use correct syntax with -n option

   The option -n 5 specifies to show 5 lines. So tail -n 5 log.txt is correct.

3. Final Answer:

   tail -n 5 log.txt -> Option A

4. Quick Check:

   tail -n 5 shows last 5 lines [OK]

Hint: Use -n with tail to specify number of lines [OK]

Common Mistakes:

• Using head instead of tail
• Omitting -n option
• Using tail without -n for line count

3. Given a file data.txt with 20 lines, what will be the output of head -n 3 data.txt | tail -n 2?

medium

A. Lines 2 and 3 of data.txt

B. Lines 1 and 2 of data.txt

C. Lines 18 and 19 of data.txt

D. Lines 3 and 4 of data.txt

Solution

1. Step 1: Understand head -n 3 data.txt

   This command outputs the first 3 lines: lines 1, 2, and 3.

2. Step 2: Apply tail -n 2 on the output

   tail -n 2 takes the last 2 lines of the previous output, so lines 2 and 3.

3. Final Answer:

   Lines 2 and 3 of data.txt -> Option A

4. Quick Check:

   head 3 then tail 2 = lines 2 & 3 [OK]

Hint: Pipe head then tail to slice lines from start [OK]

Common Mistakes:

• Assuming tail works on whole file, not head output
• Confusing line numbers
• Thinking tail -n 2 shows first 2 lines

4. You run head -n 5 file.txt but get an error: head: invalid option -- 'n'. What is the likely cause?

medium

A. The file file.txt does not exist

B. The head command version does not support -n

C. You need to use --lines=5 instead of -n 5

D. You must run the command as root

Solution

1. Step 1: Analyze the error message

   The error says invalid option -- 'n', meaning -n is not recognized.

2. Step 2: Understand command version differences

   Some older or non-GNU versions of head do not support -n and require different syntax.

3. Final Answer:

   The head command version does not support -n -> Option B

4. Quick Check:

   Invalid option error means unsupported flag [OK]

Hint: Check command version if options cause errors [OK]

Common Mistakes:

• Assuming file missing causes option error
• Trying to run as root unnecessarily
• Using wrong syntax without checking version

5. You want to monitor the last 15 lines of a growing log file app.log in real-time but only want to see the newest lines as they appear. Which command combination is best?

hard

A. head -n 15 app.log

B. tail -n 15 app.log

C. tail -n 15 -f app.log

D. head -n 15 -f app.log

Solution

1. Step 1: Understand the need to see last lines and follow updates

   You want the last 15 lines and to watch new lines as they are added.

2. Step 2: Use tail with -n 15 and -f

   tail -n 15 -f app.log shows last 15 lines and follows file changes live.

3. Final Answer:

   tail -n 15 -f app.log -> Option C

4. Quick Check:

   tail -n 15 -f = last 15 lines + live updates [OK]

Hint: Use tail -f to follow file changes live [OK]

Common Mistakes:

• Using head which shows start, not end
• Omitting -f to follow updates
• Using head -f which is invalid