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.
Which THREE of the following commands can be used to search for a string in multiple files and display the matching lines?
find /path -name '*.txt' -type f
Why wrong: Finds files, not content.
ack 'pattern' /path
Similar to grep, recursive.
grep -r 'pattern' /path
Recursive search.
rg 'pattern' /path
ripgrep searches for patterns.
sort /path/file
Why wrong: Sorts lines, does not search.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ack 'pattern' /path
Option B is correct because `ack` is a Perl-based grep replacement that recursively searches for a pattern in files under a given path, displaying matching lines by default. It is designed for source code and text files, making it a valid tool for this task.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
find /path -name '*.txt' -type f
Why it's wrong here
Finds files, not content.
ack 'pattern' /path
Why this is correct
Similar to grep, recursive.
Related concept
Read the scenario before looking for a memorised answer.
grep -r 'pattern' /path
Why this is correct
Recursive search.
Related concept
Read the scenario before looking for a memorised answer.
rg 'pattern' /path
Why this is correct
ripgrep searches for patterns.
Related concept
Read the scenario before looking for a memorised answer.
sort /path/file
Why it's wrong here
Sorts lines, does not search.
Common exam traps
The trap here is that candidates may confuse file-location commands like `find` with content-search commands, or assume that `sort` can filter lines based on a pattern, when it only reorders lines.
Detailed technical explanation
Under the hood, `grep -r` uses the Boyer-Moore algorithm for fast pattern matching, while `rg` (ripgrep) leverages Rust's SIMD instructions and memory-mapped I/O for even faster searches, especially in large codebases. `ack` automatically skips version control directories like `.git` and ignores binary files by default, which can be a subtle advantage over `grep -r` in real-world projects.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
The correct answer is: ack 'pattern' /path — Option B is correct because `ack` is a Perl-based grep replacement that recursively searches for a pattern in files under a given path, displaying matching lines by default. It is designed for source code and text files, making it a valid tool for this task.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
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