diff for file comparison in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to compare two files named file1.txt and file2.txt using the diff command.

Linux CLI

diff [1] file2.txt

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

Afile1.txt

B-u

C-r

D--help

Attempts:

3 left

💡 Hint

Common Mistakes

Using an option like -u instead of the file name.

Forgetting to specify the first file.

The diff command compares two files. The first argument should be the first file name, here 'file1.txt'.

2fill in blank

medium

Complete the code to show unified diff output between file1.txt and file2.txt.

Linux CLI

diff [1] file1.txt file2.txt

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

A--brief

B-c

C-r

D-u

Attempts:

3 left

💡 Hint

Common Mistakes

Using -r which is for recursive directory comparison.

Using --brief which only shows if files differ, not the details.

The -u option shows unified diff format, which is easier to read.

3fill in blank

hard

Fix the error in the command to compare directories dir1 and dir2 recursively.

Linux CLI

diff [1] dir1 dir2

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

A-r

B-u

C-c

D-q

Attempts:

3 left

💡 Hint

Common Mistakes

Using -u or -c which are for file diffs, not recursive directory comparison.

Using -q which only reports if files differ, no details.

The -r option tells diff to compare directories recursively.

4fill in blank

hard

Fill both blanks to create a command that shows only if files differ between dirA and dirB recursively.

Linux CLI

diff [1] [2] dirA dirB

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

A-r

B-q

C-u

D-c

Attempts:

3 left

💡 Hint

Common Mistakes

Using -u or -c which show detailed diffs, not just if files differ.

Omitting -r when comparing directories.

The -r option compares directories recursively, and -q shows only if files differ without details.

5fill in blank

hard

Fill all three blanks to create a command that ignores case differences and shows unified diff between fileA.txt and fileB.txt.

Linux CLI

diff [1] [2] [3] fileA.txt fileB.txt

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

A-i

B-u

C-w

D-r

Attempts:

3 left

💡 Hint

Common Mistakes

Using -r which is for directories, not files.

Omitting -i when ignoring case is needed.

The -i option ignores case differences, -u shows unified diff, and -w ignores all whitespace differences.

Practice

1. What does the diff command do in Linux?

easy

A. It copies files from one directory to another.

B. It deletes duplicate files automatically.

C. It merges two files into one.

D. It compares two files line by line and shows differences.

Solution

1. Step 1: Understand the purpose of diff

   The diff command is used to compare files line by line.

2. Step 2: Identify what diff outputs

   It shows the differences between two files, not deleting, merging, or copying.

3. Final Answer:

   It compares two files line by line and shows differences. -> Option D

4. Quick Check:

   diff compares files [OK]

Hint: Remember: diff shows differences, it does not merge or delete [OK]

Common Mistakes:

• Thinking diff merges files
• Confusing diff with copy or delete commands
• Assuming diff modifies files

2. Which of the following is the correct **basic** syntax to compare two files file1.txt and file2.txt using diff?

easy

A. diff file1.txt file2.txt

B. diff -c file1.txt file2.txt

C. diff file1.txt > file2.txt

D. diff -r file1.txt file2.txt

Solution

1. Step 1: Identify basic diff syntax

   The basic syntax to compare two files is diff file1 file2.

2. Step 2: Understand options

   diff -c file1.txt file2.txt uses -c (context), which is valid but not basic syntax. diff file1.txt > file2.txt redirects output incorrectly. diff -r file1.txt file2.txt (-r) is for directories.

3. Final Answer:

   diff file1.txt file2.txt -> Option A

4. Quick Check:

   Basic diff syntax [OK]

Hint: Basic diff syntax: diff file1 file2 [OK]

Common Mistakes:

• Using redirection instead of arguments
• Confusing directory options with file comparison
• Adding unnecessary flags for simple comparison

3. Given two files with these contents:

file1.txt:
apple
banana
cherry

file2.txt:
apple
banana
date

What will be the output of diff file1.txt file2.txt?

medium

A. 2c2
< banana
---
> banana

B. No output (files are identical)

C. 3c3
< cherry
---
> date

D. Error: files not found

Solution

1. Step 1: Compare lines one by one

   Lines 1 and 2 are the same (apple, banana). Line 3 differs: 'cherry' vs 'date'.

2. Step 2: Understand diff output format

   diff shows line number and change type: '3c3' means line 3 changed. Then shows old line with '<' and new line with '>'.

3. Final Answer:

   3c3 < cherry --- > date -> Option C

4. Quick Check:

   Line 3 differs [OK]

Hint: Look for first differing line number in diff output [OK]

Common Mistakes:

• Assuming diff shows all lines
• Confusing line numbers in output
• Expecting no output for different files

4. You run diff file1.txt file2.txt but get the error: diff: file2.txt: No such file or directory. What is the most likely cause?

medium

A. file2.txt does not exist in the current directory.

B. You used wrong syntax for diff command.

C. file1.txt is empty.

D. You do not have permission to read file1.txt.

Solution

1. Step 1: Analyze the error message

   The error says file2.txt: No such file or directory, meaning file2.txt is missing or path is wrong.

2. Step 2: Check other options

   Wrong syntax would cause different errors. Empty file1.txt or permission issues on file1.txt won't cause missing file2.txt error.

3. Final Answer:

   file2.txt does not exist in the current directory. -> Option A

4. Quick Check:

   Missing file error [OK]

Hint: Check file existence if diff says 'No such file' [OK]

Common Mistakes:

• Assuming syntax error causes missing file message
• Ignoring file path or directory
• Confusing permission errors with missing files

5. You want to compare two directories dir1 and dir2 recursively to find all file differences. Which diff command should you use?

hard

A. diff -c dir1 dir2

B. diff -r dir1 dir2

C. diff dir1 dir2

D. diff -i dir1 dir2

Solution

1. Step 1: Understand recursive comparison

   The -r option tells diff to compare directories recursively.

2. Step 2: Check other options

   -c is context output, not recursive. No option means file comparison only. -i ignores case, not recursive.

3. Final Answer:

   diff -r dir1 dir2 -> Option B

4. Quick Check:

   Recursive directory diff [OK]

Hint: Use -r to compare directories recursively with diff [OK]

Common Mistakes:

• Using -c expecting recursion
• Omitting -r for directory comparison
• Confusing -i with recursive option