Combine multiple csv files with filenames in it as rows on mac terminal

Question

I have multiple csv files. I want to combine them in a single file and doing it like this on terminal;

"cat *.csv >combined.csv"

This works, but I need to add filenames to all of this csv files before merging in order to understand the source of data in the combined version. Now, I have this as combined;

a1, a2, a3, a4
b1, a2, a3, a4

I want to add filenames as rows to the beginning

file1, a1, a2, a3, a4
file2, b1, a2, a3, a4

Is there any way to do that on mac terminal?

Answer 1

You can create a shell script

#!/bin/sh

rm combined.csv
for f in *.csv
do
  sed -e "s/^/${f},/" $f >> combined.csv
done

It will produce the following in the combined.csv file:

file1.csv,a1, a2, a3, a4
file2.csv,b1, a2, a3, a4