jefferickson / cn

A CLI tool to extract a column from a CSV

DEPRECATION NOTICE

I recently discovered the tool Miller (https://github.com/johnkerl/miller) and believe it to be a better tool for this job. It does what cn set out to accomplish and so much more. Therefore I am archiving this project and removing the Homebrew tap.

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cn

Usage: cn [-d] [-h HEADERFILE] LABEL FILE

A handy little utility to give you the index (1-based) of a label/column name in a header of a CSV. Using the -d flag, only the data under the label/column name is returned.

For example:

$ cat data.csv
a,b,c
1,0,0
0,1,0
0,0,1

$ cn b data.csv
2

$ cn -d b data.csv
0
1
0

You can also use stdin:

$ cat data.csv | cn b -
2

$ cat data.csv | cn -d b -
0
1
0

This works well with other tools, e.g.:

$ cat data2.csv
a,b,c
1,2,3
4,5,6
7,8,9

$ cat data2.csv | cn -d b - | awk -F, '{s+=$1}END{print s}'
15

You can even provide the headers from another file, which works well when you are filtering data (coming in from grep via stdin, for example) and still want to select a column. For example, let's say you have the following data. You want to sum the metric_2 column for all rows with type == 'a':

$ cat data3.csv
type,metric_1,metric_2,metric_3
a,1,2,3
b,4,5,6
a,7,8,9

$ cat data3.csv | grep a | cn -h data3.csv -d metric_2 - | awk -F, '{s+=$1}END{print s}'
10

Installation

You can install easily with homebrew:

brew tap jefferickson/cn
brew install cn

Or from source:

go get github.com/jefferickson/cn
go install github.com/jefferickson/cn