This LFCS practice question tests your understanding of essential commands. 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.
An administrator needs to replace all occurrences of the string 'foo' with 'bar' in all files under /etc/config, but only in files ending with .conf. The replacement must be done in-place, and backup copies should be created with a .bak extension. Which command accomplishes this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
find /etc/config -name '*.conf' -exec sed -i.bak 's/foo/bar/g' {} +
Option C is correct because it uses `sed -i.bak` which creates a backup file with the .bak extension before performing the in-place substitution, and the `find -exec ... +` variant efficiently processes multiple files at once. The `-i` option with an argument (no space) specifies the backup suffix directly, satisfying the requirement for backup copies.
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.
find /etc/config -name '*.conf' -exec sed 's/foo/bar/g' {} \;
Why it's wrong here
Prints to stdout, no in-place modification.
✓
find /etc/config -name '*.conf' -exec sed -i.bak 's/foo/bar/g' {} +
Why this is correct
-i.bak creates backup with .bak extension.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
find /etc/config -name '*.conf' -exec sed -i 's/foo/bar/g' {} +
Why it's wrong here
Does not create backup files.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the syntax `-i .bak` (with a space, which is incorrect) with `-i.bak` (no space, which is correct), or they forget that `-i` without a suffix does not create backups, leading them to choose options that either fail or omit the required backup step.
Detailed technical explanation
How to think about this question
The `-i` option in sed (stream editor) modifies files in-place by writing to a temporary file and then renaming it; when a suffix is provided (e.g., `-i.bak`), the original file is first copied to that backup name. The `find -exec ... +` variant collects as many file paths as possible into a single command invocation, reducing process spawns and improving performance over `\;` which runs a separate sed process per file. This is especially important when dealing with large numbers of .conf files under /etc/config.
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 LFCS 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.
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: find /etc/config -name '*.conf' -exec sed -i.bak 's/foo/bar/g' {} + — Option C is correct because it uses `sed -i.bak` which creates a backup file with the .bak extension before performing the in-place substitution, and the `find -exec ... +` variant efficiently processes multiple files at once. The `-i` option with an argument (no space) specifies the backup suffix directly, satisfying the requirement for backup copies.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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