Read write text file in shell

#!/bin/bash
contains() {
    string="$1"
    substring="$2"
    if test "${string#*$substring}" != "$string"
    then
        return 0    # $substring is in $string
    else
        return 1    # $substring is not in $string
    fi
}


file=$1
dest=$2
rm $dest
while IFS= read -r line
do
        # display $line or do somthing with $line
        echo "$line" >> "$dest"


        contains "$line" ",ABC," && echo $line | sed -e "s/,ABC,/,ZRM,/g" >> "$dest"
       
done <"$file"