reem000.sh

#!/bin/bash

function goCsv {
  local IFS=,
  while read row; do
    local output=
    columns=($row)
    for c in "${columns[@]}"; do
      if [ "${c}" == "" ]; then
        c="AAA"
      fi
      if [ "${output}" == "" ]; then
        output="${c}"
      else
        output="${output},${c}"
      fi
    done
    echo "${output}"
  done < data.csv
}

goCsv