How to count the number of consecutive identical lines

Joe Jobs

4/21/23, 9:03 PM

I have a file that looks like this:

I need a script to show me this:

2000 - 2
2001 - 4
2002 - 2

I prefer using sed or awk

0 + 0

sed

awk

text-processing

steeldriver

4/21/23, 9:07 PM

This sounds like exactly what `uniq -c` was invented for ...

Joe Jobs

4/21/23, 9:16 PM

Oh nice I did not know that. Thanks!

bac0n

4/22/23, 8:06 AM

`uniq -c file | sed -rn 's/ *([0-9]+) (.*)/\2 - \1/p'`

Score:1

Ubuntu

terdon

4/22/23, 8:59 AM

This is precisely what uniq -c does. From man uniq:

DESCRIPTION

Filter adjacent matching lines from INPUT (or standard input), writing to OUTPUT (or standard output).

[ . . . ]

-c, --count
prefix lines by the number of occurrences

So with your example, we get:

$ uniq -c file
      2 2000
      4 2001
      2 2002

You can also write a little script if you prefer for some reason. For instance, with awk:

$ awk '{ count[$0]++ } END{ for(line in count){ print line,count[line] }}' file 
2000 2
2001 4
2002 2

0 + 0

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: How to count the number of consecutive identical lines

TH: วิธีนับจำนวนบรรทัดที่เหมือนกันติดต่อกัน

RO: Cum se numără numărul de linii identice consecutive

RU: Как подсчитать количество последовательных одинаковых строк

VI: Cách đếm số dòng giống nhau liên tiếp

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