uniq, comm Examples

uniq - report or omit repeated lines

uniq [OPTION]... [INPUT [OUTPUT]]

-c: prefix lines by the number of occurrences
-d: print duplicate lines, one for each group
-i: ignore differences in case when comparing
-f <num>: avoid comparing the first <num> fields
-s: avoid comparing the first N characters
-u: only print unique lines

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comm - compare two sorted files line by line

comm [OPTION]... FILE1 FILE2

When FILE1 or FILE2 (not both) is -, read standard input.

-1: suppress column 1 (lines unique to FILE1)
-2: suppress column 2 (lines unique to FILE2)
-3: suppress column 3 (lines that appear in both files)

• show all cities, only visited by me, by, you, and by both of us
  comm visited-by-me.txt visited-by-you.txt
  [Output]

• show all cities, only visited by you
  comm -1 -3 visited-by-me.txt visited-by-you.txt
  [Output]

• reports, how often the names in ../data/names.txt exists (prerequisite: name entries must be sorted)
  uniq -c ../data/names.txt
  [Output]

• reports, how often the names in ../data/names.txt exists (no prerequisite)
  sort ../data/names.txt | uniq -c
  [Output]