diff for file comparison in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of diff command with two similar files

Given two files file1.txt and file2.txt with the following contents:

file1.txt:
apple
banana
cherry

file2.txt:
apple
banana
date

What is the output of the command diff file1.txt file2.txt?

A No output

B

2c2
< banana
---
> banana

C

3c3
< cherry
---
> date

D

1a2
> banana

💡 Hint

Look for the line number where the files differ and how diff shows changes.

The diff command shows that line 3 differs: 'cherry' in file1.txt is replaced by 'date' in file2.txt. The output format is 'c' followed by the differing lines.

💻 Command Output

intermediate

Using diff with -u option

What is the main difference in output when running diff -u file1.txt file2.txt compared to diff file1.txt file2.txt for two files with small differences?

A Only line numbers where files differ without content

B No output if files differ

C Output in reverse order of lines

D Unified diff format showing context lines with '+' and '-' prefixes

💡 Hint

The -u option is often used for patches and shows more context.

The -u option produces a unified diff format that shows lines before and after the change with '+' for additions and '-' for deletions, making it easier to understand changes.

💻 Command Output

advanced

Output of diff with binary files

What output does the command diff file1.bin file2.bin produce if both files are binary and differ?

A Line by line text differences

B Binary files file1.bin and file2.bin differ

C Syntax error

D No output

💡 Hint

diff handles binary files differently than text files.

When diff detects binary files that differ, it outputs a simple message stating the files differ without showing line differences.

🔧 Debug

advanced

Why does diff show no output for two different files?

You run diff fileA.txt fileB.txt but see no output, even though you know the files differ. Which of the following is the most likely reason?

A The files differ only in whitespace and diff is run with default options

B The files are identical

C The diff command is broken

D The files have different names

💡 Hint

No output from diff means the files are identical.

diff produces no output when the two files are identical. However, if the files differ only in whitespace and diff is run with default options, it may also produce no output.

🚀 Application

expert

Automate file difference report generation

You want to create a script that compares two directories dir1 and dir2 recursively and outputs a unified diff for each differing file into a single report file diff_report.txt. Which command pipeline best achieves this?

A diff -ur dir1 dir2 > diff_report.txt

B diff -r dir1 dir2 | tee diff_report.txt

C diff -u dir1 dir2 > diff_report.txt

D diff dir1 dir2 > diff_report.txt

💡 Hint

You need recursive comparison with unified diff format.

The -r option makes diff recursive, and -u produces unified diff format. Redirecting output to a file saves the report.