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I have file file.txt which look like this

a
b
b
c
c
c

I want to know the command to which get file.txt as input and produces the output

a 1
b 2
c 3
e271p314
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3 Answers3

4

I think uniq is the command you are looking for. The output of uniq -c is a little different from your format, but this can be fixed easily.

$ uniq -c file.txt
      1 a
      2 b
      3 c
kirelagin
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2

If you want to count the occurrences you can use uniq with -c.

If the file is not sorted you have to use sort first

$ sort file.txt | uniq -c
1 a
2 b
3 c

If you really need the line first followed by the count, swap the columns with awk

$ sort file.txt | uniq -c | awk '{ print $2 " " $1}'
a 1
b 2
c 3
Matteo
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0

You can use this awk:

awk '!seen[$0]++{ print $0, (++c) }' file
a 1
b 2
c 3

seen is an array that holds only uniq items by incrementing to 1 first time an index is populated. In the action we are printing the record and an incrementing counter.

Update: Based on comment below if intent is to get a repeat count in 2nd column then use this awk command:

awk 'seen[$0]++{} END{ for (i in seen) print i, seen[i] }' file
a 1
b 2
c 3
anubhava
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    This won't work, it only appears to work on OP's example because the letters increase by 1 each time, how could you possibly print the number of unique lines before getting to the end of the file ? – 123 Jul 02 '15 at 11:08
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    I may not have understood the question and it is not clear if 2nd column is incrementing counter (as I interpreted) or a repeat count – anubhava Jul 02 '15 at 11:09
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    We don't know what OP requires. Whether just indexing + uniq, or count – anishsane Jul 02 '15 at 11:10
  • @anubhava Pretty sure from context of the question that it is the number of unique occurences of each line, but I'll retract my downvote for now as i hadn't considered the other interpretation :) – 123 Jul 02 '15 at 11:11
  • Thanks, in any case I've added an addendum in my answer to take care of repeat counts (in case). – anubhava Jul 02 '15 at 11:15