This LFCS practice question tests your understanding of essential commands. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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.
A system administrator wants to display a list of all currently running processes with their parent process IDs. Which command is most 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.
pstree
Why wrong: Shows process tree but not a simple list with PPIDs.
jobs
Why wrong: Displays shell jobs, not all processes.
top
Why wrong: Interactive process viewer; does not show PPID by default.
ps -ef
Shows all processes with parent PID in the PPID column.
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 -ef
Option D (ps -ef) is correct because the 'ps' command with the '-e' flag displays all processes, and the '-f' flag provides a full-format listing that includes the PPID (parent process ID) in the output. This directly meets the requirement to list all currently running processes with their parent process IDs.
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.
pstree
Why it's wrong here
Shows process tree but not a simple list with PPIDs.
jobs
Why it's wrong here
Displays shell jobs, not all processes.
top
Why it's wrong here
Interactive process viewer; does not show PPID by default.
ps -ef
Why this is correct
Shows all processes with parent PID in the PPID column.
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.
Common exam traps
The trap here is that candidates may confuse 'pstree' (which shows parent-child relationships visually) with 'ps -ef' (which lists numeric PPIDs), or assume 'top' is suitable for a static list, when the question specifically asks for a list with parent process IDs, not a tree or dynamic view.
Trap categories for this question
Command / output trap
Shows process tree but not a simple list with PPIDs.
Detailed technical explanation
The 'ps -ef' command reads process information from the /proc filesystem, which contains directories for each process ID (PID) with files like 'status' and 'stat' that include the PPID. The '-f' flag triggers a full-format output that includes columns for UID, PID, PPID, C (CPU utilization), STIME (start time), TTY, TIME, and CMD. In real-world scenarios, administrators often use 'ps -ef' to trace process ancestry or identify orphan processes, where the PPID becomes 1 (init) if the parent has terminated.
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
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
The correct answer is: ps -ef — Option D (ps -ef) is correct because the 'ps' command with the '-e' flag displays all processes, and the '-f' flag provides a full-format listing that includes the PPID (parent process ID) in the output. This directly meets the requirement to list all currently running processes with their parent process IDs.
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
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