This prepends a header file to each matching file, recursively on the file system.

license_header_prepender.sh

#!/bin/bash

DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

IFS=$'\n'
for f in $(find . -name '*.cs')
do
  if ! grep -q Copyright "$f"
  then
    cat "$DIR"/copyright_header.txt "$f" >"$f".new && mv "$f".new "$f"
  fi
  echo "$f"
done