Add license headers to source files. This example adds the Apache header to Golang files.

addlicense.sh

#!/bin/bash
set -eu -o pipefail

# This script ensures source code files
# have copyright license headers.
#
# It modifies all source files in place
# and avoids adding a license header
# to any file that already has one.

header=(
	'// Copyright 2024 Cock&Balls LLC'
	'//'
	'// Licensed under the Apache License, Version 2.0 (the "License");'
	'// you may not use this file except in compliance with the License.'
	'// You may obtain a copy of the License at'
	'//'
	'//     http://www.apache.org/licenses/LICENSE-2.0'
	'//'
	'// Unless required by applicable law or agreed to in writing, software'
	'// distributed under the License is distributed on an "AS IS" BASIS,'
	'// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.'
	'// See the License for the specific language governing permissions and'
	'// limitations under the License.'
)

realpath=$(realpath -- "$0")
cd "${realpath%/*}"

checked=0
updated=0

shopt -s globstar

for file in **/*.go; do

	checked=$((checked+1))

	# skip if the file contains the exact header
	changed=0
	for (( i=0; i < ${#header[@]}; i++ )); do
		IFS= read -r line
		[[ $line != "${header[$i]}" ]] && changed=1 && break
	done < "$file"
	[[ $changed == 0 ]] && continue

	# check whether the file starts with a copyright header
	in_header=0
	IFS= read -r line < "$file"
	[[ $line == '//'*'Copyright'* ]] && in_header=1

	# add the new copyright header, replacing the existing one, if any
	lines=()
	while IFS= read -r line; do
		if [[ $in_header == 1 ]] && [[ $line != '//'* ]]; then
			in_header=0
		fi
		if [[ $in_header == 0 ]]; then
			lines+=("$line")
		fi
	done < "$file"
	printf '%s\n' "${header[@]}" '' "${lines[@]}" | gofmt > "$file"

	echo "updated $file"
	updated=$((updated+1))
done

echo
echo "checked $checked files."
echo "updated $updated files."