You don't need a script for such a simple thing. You can use awk:

awk '$2 ~ "^[0-9][0-9]*$" { print $2 }' file.txt | head -n -1 | awk '{print}' ORS=',' | sed 's/,$/

/'

Some explanations:

• awk '$2 ~ "^[0-9][0-9]*$" { print $2 }' file.txt - print from the file.txt only the fields which are numbers.


• head -n -1 - remove last line / last number.


• awk '{print}' ORS=',' - concatenate all lines in one single line, each number separated by ,.


• sed 's/,$/
/' - replace last , with a newline character.

Or, shorter:

awk '$2 ~ "^[0-9][0-9]*$" { print $2 }' ORS=',' file.txt | sed 's/,[0-9]*,$/

/'