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uniq

Q: What does uniq do?

Filter or count adjacent duplicate lines in sorted input. uniq removes or counts duplicate lines, but only works on adjacent duplicates — always sort first. Combined with sort | uniq -c | sort -rn, it produces frequency counts of any text data.

Filter or count adjacent duplicate lines in sorted input.

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interactive breakdown — edit the command and press Explain

What it does

uniq removes or counts duplicate lines, but only works on adjacent duplicates — always sort first. Combined with sort | uniq -c | sort -rn, it produces frequency counts of any text data.

Common flags

Flag	Meaning
`-c` `--count`	Prefix lines with occurrence count
`-d` `--repeated`	Print only duplicate lines
`-u` `--unique`	Print only unique lines
`-i` `--ignore-case`	Ignore case when comparing

Examples

sort access.log | uniq -c | sort -rn | head -10Top 10 most frequent log lines · explain & risk-check →

sort ips.txt | uniq -dShow IPs that appear more than once · explain & risk-check →

sort errors.log | uniq -uShow lines that appear exactly once · explain & risk-check →

Pro tip

The pattern `sort | uniq -c | sort -rn` is one of the most powerful one-liners in DevOps — use it to analyze access logs, error frequencies, or any text data.

sort grep awk

Open the full explainer →More in Text Processing

Reference text is hand-written and may be incomplete — check man uniq for your version. Test destructive commands on a non-production system first.