Bash 5 reference · Text and System Tools

uniq (Linux command)

Remove or count adjacent duplicate lines; sort first, then use -c to count occurrences or -d to show only duplicates.

Bash 5

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Syntax

uniq [-c] [-d] [-u] [FILE]

Parameter	Description
`-c`	Prefix lines with counts.
`-d / -u`	Only duplicated / only unique lines.

Count occurrences

printf '/a\n/b\n/a\n/a\n' | sort | uniq -c | sort -rn

Output

      3 /a
      1 /b

Run this on your computer — see “Get Started” for setup.

Show duplicates

printf 'x\nx\ny\n' | uniq -d

Output

Run this on your computer — see “Get Started” for setup.

sort · Sort lines alphabetically, numerically, in reverse, by a key column, or with human-readable sizes; -u removes duplicates.
Bash sort, uniq, cut and tr · tutorial