The correct answer identifies that sed -n '3,5p' file.txt prints lines 3 to 5, as the -n flag suppresses automatic output and the p command explicitly prints only the specified range. This is true because sed operates as a stream editor, processing text line by line, and the combination of -n with the address range and print command gives you precise control over which lines appear in the output. On the LPIC-1 exam, this tests your understanding of sed command options and usage, particularly how flags like -i for in-place editing and substitution syntax like 's/foo/bar/g' modify files directly rather than just displaying changes. A common trap is confusing -n with -i: remember that -n silences output, while -i writes changes back to the file. For memory, think "n for no print unless told, i for in-file edit."
LPIC-1 Shells, Scripting and Data Management Practice Question
This LPIC-1 practice question tests your understanding of shells, scripting and data management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which THREE statements are true about the sed command?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
sed -i 's/foo/bar/g' file.txt replaces all occurrences of foo with bar in the file.
Option B is correct because the `-i` flag in sed enables in-place editing, directly modifying the file rather than just outputting changes to stdout. The substitution command `'s/foo/bar/g'` replaces all occurrences of `foo` with `bar` globally on each line, and with `-i`, the changes are written back to the file.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
sed 's/old/new/g' file.txt permanently changes the file.
Why it's wrong here
Without -i, sed outputs to stdout, does not change the file.
✓
sed -i 's/foo/bar/g' file.txt replaces all occurrences of foo with bar in the file.
Why this is correct
-i makes in-place changes.
Related concept
Read the scenario before looking for a memorised answer.
✗
sed uses extended regular expressions by default.
Why it's wrong here
By default, sed uses basic regular expressions; -E enables extended.
✓
sed '/^#/d' file.txt deletes lines that start with #.
Why this is correct
The address /^#/ matches lines starting with #, d deletes them.
Related concept
Read the scenario before looking for a memorised answer.
✓
sed -n '3,5p' file.txt prints lines 3 to 5 of file.txt.
Why this is correct
-n suppresses output, p prints specified lines.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume sed always modifies files in place, forgetting that without `-i`, sed only outputs to stdout, and that sed defaults to basic regular expressions, not extended ones.
Trap categories for this question
Command / output trap
Without -i, sed outputs to stdout, does not change the file.
Detailed technical explanation
How to think about this question
Under the hood, sed operates as a stream editor, reading input line by line into a pattern space, applying commands, and then outputting the result. The `-i` option works by creating a temporary file, writing the modified output to it, and then renaming it over the original, which is why it can be risky if the command fails mid-process. In real-world scripting, always test without `-i` first, then add it once the pattern is verified, to avoid accidental data loss.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the LPIC-1 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Shells, Scripting and Data Management — This question tests Shells, Scripting and Data Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: sed -i 's/foo/bar/g' file.txt replaces all occurrences of foo with bar in the file. — Option B is correct because the `-i` flag in sed enables in-place editing, directly modifying the file rather than just outputting changes to stdout. The substitution command `'s/foo/bar/g'` replaces all occurrences of `foo` with `bar` globally on each line, and with `-i`, the changes are written back to the file.
What should I do if I get this LPIC-1 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO commands can be used to count the number of lines in a file named 'data.txt'?
hard
✓ A.wc -l data.txt
✓ B.awk 'END{print NR}' data.txt
C.cat data.txt | wc -c
D.grep -c '.*' data.txt
E.sed -n '$=' data.txt
Why A: Option A is correct because `wc -l` specifically counts the number of newline characters in the file, which corresponds to the number of lines. Option B is correct because `awk 'END{print NR}'` processes the file line by line, and the built-in variable `NR` holds the total number of records (lines) processed when the END block is executed, thus outputting the line count.
Last reviewed: Jun 11, 2026
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This LPIC-1 practice question is part of Courseiva's free LPI certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LPIC-1 exam.
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