This LFCS practice question tests your understanding of operation of running systems. 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 engineer wants to list all processes currently running under user 'appuser'. Which command is appropriate?
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.
pgrep -u appuser
Why wrong: Lists only PIDs, not full process info.
ps -u appuser
Lists all processes for appuser.
top -u appuser
Why wrong: Interactive, not a one-shot listing.
ps aux | grep appuser
Why wrong: Works but less efficient and may match unwanted lines.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ps -u appuser
Option B is correct because the `ps -u appuser` command lists all processes owned by the user 'appuser' by filtering the process table based on the user's UID. The `-u` option selects processes whose effective user ID or name matches the given argument, making it the most straightforward and standard way to display processes for a specific user.
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.
pgrep -u appuser
Why it's wrong here
Lists only PIDs, not full process info.
ps -u appuser
Why this is correct
Lists all processes for appuser.
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.
top -u appuser
Why it's wrong here
Interactive, not a one-shot listing.
ps aux | grep appuser
Why it's wrong here
Works but less efficient and may match unwanted lines.
Common exam traps
The trap here is that candidates often choose `ps aux | grep appuser` because it seems intuitive, but they overlook that `grep` matches any field, not just the user column, and can produce misleading results or miss processes if the username is part of a command string.
Detailed technical explanation
The `ps` command reads process information from the `/proc` filesystem on Linux, where each running process has a directory named by its PID containing metadata like `/proc/[pid]/status` (which includes the UID). The `-u` option internally matches against the real user ID (RUID) or effective user ID (EUID) depending on the `ps` variant, but in standard Linux `ps` from procps-ng, it filters by the effective user ID. In real-world scenarios, using `ps -u appuser` is preferred over `pgrep` when you need full process details for debugging or auditing, while `pgrep` is better for scripting where only PIDs are needed.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Operation of Running Systems — This question tests Operation of Running Systems — Read the scenario before looking for a memorised answer..
The correct answer is: ps -u appuser — Option B is correct because the `ps -u appuser` command lists all processes owned by the user 'appuser' by filtering the process table based on the user's UID. The `-u` option selects processes whose effective user ID or name matches the given argument, making it the most straightforward and standard way to display processes for a specific user.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
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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