package main

import (
	"os"
	"bufio"
)

const SEP = '\n'

func lineChangeFunction(line string) string {
	return line
}

func changeFile(inputFilename string, outputFilename string, lineChangeFunction func(string) string) bool {
	inputFile, err := os.Open(inputFilename, os.O_RDONLY, 0)
	if err != nil {
		return false
	}
	defer inputFile.Close()
	outputFile, err := os.Open(outputFilename, os.O_WRONLY|os.O_CREAT|os.O_TRUNC, 0666)
	if err != nil {
		return false
	}
	defer outputFile.Close()
	in := bufio.NewReader(inputFile)
	for {
		line, err := in.ReadSlice(SEP);
		if err != nil {
			break
		};
		outputFile.WriteString(lineChangeFunction(string(line)))
	}
	return true
}

func main() {
	changeFile("input.txt", "output.txt", lineChangeFunction)
}