Shell command for replacing all texts in all files under specified paths

sed-inplace.sh

sed-inplace () {
    if (( $# < 2 )); then
        echo "sed-inplace FROM TO [PATH ...]"
        return 1
    fi
    from="$1"
    to="$2"
    shift 2
    ag -l "$from" "$@" | while read file; do
      if [ "`uname`" = "Darwin" ]; then # please, please give me portable sed...
        sed -i '' -e "s/$from/$to/g" "$file"
      else
        sed -i'' -e "s/$from/$to/g" "$file"
      fi
    done
}