I am writing a script to setup a csv file with data parsed from another .txt file. I have a few particular columns, and how this program flows, I am using these columns to grab data from the .txt. I am just unsure on how to proceed, since I want the next column to be tied to the current iteration of things Im looking at.

The general code I have is like this:

COLUMNS=(1 2 3) 

for column in "${COLUMNS[@]}"; do
   echo "${COLUMNS[@]}" > someCSVFile.csv
   parsedText = $(sed -n '/'$column-'/,/^${/^$/d; p}' someTextFile.txt)
   for line in "${parsedText[@]}"; do
      echo "${line}" >> someCSVFile.csv
   done
done 

When I parse the code, The text returns in a format like:

a
b
c

Which ideally, I should pass to the CSV in the second for loop which should be like:

1,2,3
a,a,a
b,b,b
c,c,c

But instead, the output will be:

1
a
b
c
2
a
b
c
3
a
b
c

Is there a way, based on iteration of the loop, that I can move to the next column of the csv?