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 find the process ID of the cron daemon. Which combination of commands is most effective?
top -p $(pgrep cron)
Why wrong: Interactive; not just retrieving the PID.
pgrep cron
Why wrong: Also returns PIDs but can match similar names; not as precise as pidof.
pidof cron
Returns the exact PID of the cron daemon.
ps -C cron -o pid=
Why wrong: Returns the PID, but requires parsing; pidof is simpler.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
pidof cron
Option C is correct because `pidof cron` directly returns the numeric process ID(s) of the cron daemon by searching the process name in the `/proc` filesystem. It is the most straightforward command for this specific task, as it outputs only the PID without additional formatting or filtering.
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.
top -p $(pgrep cron)
Why it's wrong here
Interactive; not just retrieving the PID.
pgrep cron
Why it's wrong here
Also returns PIDs but can match similar names; not as precise as pidof.
pidof cron
Why this is correct
Returns the exact PID of the cron daemon.
Related concept
Read the scenario before looking for a memorised answer.
ps -C cron -o pid=
Why it's wrong here
Returns the PID, but requires parsing; pidof is simpler.
Common exam traps
The trap here is that candidates often choose `pgrep cron` (option B) because it seems simple, but they overlook that `pgrep` uses regex matching by default and may return multiple or incorrect PIDs, whereas `pidof` is designed for exact binary name matching.
Trap categories for this question
Similar concept trap
Also returns PIDs but can match similar names; not as precise as pidof.
Detailed technical explanation
The `pidof` command reads `/proc` to find processes by exact executable name, making it reliable for daemons like cron that run with a fixed name. In contrast, `pgrep` uses pattern matching by default, which can match partial names (e.g., 'cron' could match 'anacron' if present). On systems with multiple cron implementations (e.g., cronie vs. vixie-cron), `pidof` returns the PID of the first matching process, which is typically the daemon.
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: pidof cron — Option C is correct because `pidof cron` directly returns the numeric process ID(s) of the cron daemon by searching the process name in the `/proc` filesystem. It is the most straightforward command for this specific task, as it outputs only the PID without additional formatting or filtering.
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
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