group by 'last' value in bash

Question

I have a two-column file:

1,112
1,123
2,123
2,124
2,144
3,158
4,123
4,158
5,123

I need to know last column2 value for each column1:

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Answer 1

You can use awk delimit on , to store each $2 in an array using key as $1:

awk 'BEGIN{FS=OFS=","} {seen[$1]=$2} END{for (i in seen) print i, seen[i]}' file.csv

1,123
2,144
3,158
4,158
5,123