LPIC-1 Shells, Scripting and Data Management Practice Question
A log file access.log contains multiple entries per IP address. An administrator wants to display a list of unique IP addresses sorted by frequency (most frequent first). Which command pipeline achieves this?
⚠ Common exam trap
The trap here is that candidates often forget uniq -c outputs the count in the first column, so they mistakenly use sort -k2 to sort by frequency, or they omit the initial sort before uniq, causing incorrect counts for non-consecutive duplicates.
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
✓
awk '{print $1}' access.log | sort | uniq -c | sort -rn
It extracts the first field (IP address) with awk, sorts them to group identical IPs, counts occurrences with uniq -c, and then sorts numerically in reverse order with sort -rn to display the most frequent IPs first. The -c flag prepends a count to each unique line, and sort -rn sorts by that count descending.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
awk '{print $1}' access.log | sort | uniq | sort -rn
Why it's wrong here
Shows unique IPs sorted in reverse numeric order of IP, not by frequency.
- ✓
awk '{print $1}' access.log | sort | uniq -c | sort -rn
Why this is correct
Correctly counts IP occurrences and sorts by frequency descending.
- ✗
awk '{print $1}' access.log | sort -rn | uniq -c
Why it's wrong here
Sorts IPs in reverse before counting, which breaks grouping; uniq requires adjacent duplicates.
- ✗
awk '{print $1}' access.log | sort | uniq -c | sort -k2
Why it's wrong here
Sorts by the second field (IP), not by frequency count.
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