If you want multiple columns you need to make the variable target_id and target_idx both arrays, no?

Then there is this:

Code:

  # then, iterate over lines
  while IFS=, read -r -a line; do
    a=echo-n ${line[$target_idx]}|md5sum # if my input in target is "id"
  done
} <testfile.txt

echo$line|"$a"

You iterate over the input lines, yes, but you produce output (the echo-line) only once: after you have read all the input. This must be wrong, no? Apart from the fact that after "echo" there needs to be a space (like after any command), but i suppose that was simply a typing error.

Also this line is not correct:

Code:

a=echo-n ${line[$target_idx]}|md5sum # if my input in target is "id"

It should perhaps read:

Code:

a=$(echo -n ${line[$target_idx]}|md5sum) # if my input in target is "id"

For parametrisation via the commandline i suggest to read the man page for getopts. I have just written an example in another thread you might want to use as a starting point.

I hope this helps.

bakunin