LFCS Essential Commands Practice Question
An administrator needs to find the process ID of the cron daemon. Which combination of commands is most effective?
⚠ Common exam trap
Watch out — 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.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
pidof cron
`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.
Answer analysis
Option-by-option breakdown
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.
- ✗
ps -C cron -o pid=
Why it's wrong here
The `ps -C cron -o pid=` command is incorrect because `ps -C` filters processes by their *command name*. The `cron` daemon's executable is typically named `crond` (or similar, like `systemd-cron`), not simply `cron`. Consequently, this command would likely fail to identify the daemon's PID. It is tempting as `cron` is the service name, and this syntax would be effective if the daemon's actual command name were precisely `cron`, or for finding processes matching an exact executable name.
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Written by Johnson Ajibi, MSc IT Security
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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.