find_replace_in_files.sh

#!/usr/bin/env bash

find_files() {
    ag "$1" | cut -d: -f1 | sort | uniq
}

do_replace() {
    echo "Finding files matching orignial string $1"
    for f in $(find_files "$1"); do
        echo "  -> Replacing string in file $f"
        sed -i "s/$1/$2/g" "$f"
    done
}

do_replace OLD_0 NEW_0
do_replace OLD_1 NEW_1
# etc...