LPIC-1 Shells, Scripting and Data Management Practice Question
Which TWO commands can be used to sort the output of ps -ef by the resident set size (RSS) in descending order?
⚠ Common exam trap
Candidates often confuse the field number for RSS in `ps -ef` output (it is the 5th field, not the 3rd) and may overlook that `--sort=rss` defaults to ascending order, requiring a minus sign for descending.
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
✓
ps --sort=-rss
Only option B is correct. `ps --sort=-rss` uses the native sorting feature of `ps`, which directly sorts by RSS in descending order (using the minus sign prefix for reverse). Options A and E are incorrect because `ps -ef` does not output RSS; its fields are UID, PID, PPID, C, STIME, TTY, TIME, CMD, so sorting by the 5th field (STIME) does not sort by RSS. Option C sorts by the 3rd field (PPID), not RSS. Option D sorts by RSS but in ascending order.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ps -ef | sort -k5,5 -rn
Why it's wrong here
Incorrect. `ps -ef` does not show RSS; the 5th field is STIME, not RSS.
- ✓
ps --sort=-rss
Why this is correct
Correct. `--sort=-rss` sorts by RSS in descending order natively.
- ✗
ps -ef | sort -k3 -rn
Why it's wrong here
Incorrect. The 3rd field in `ps -ef` is PPID, not RSS.
- ✗
ps --sort=rss
Why it's wrong here
Incorrect. `--sort=rss` sorts by RSS in ascending order, not descending.
- ✗
ps -ef | sort -k5 -rn
Why it's wrong here
Incorrect. `ps -ef` does not include RSS; the 5th field is STIME.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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