Go Course : Exercise 17

modify_filecontents.go

/*
Manipulate a text file.Search for 'word' in this text file and replace it with 'inserted word'. Write the contents
back into the original file
*/
package main

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"log"
	"os"
)

func check(e error) {
	if e != nil {
		log.Fatal(e)
	}
}

func main() {
	//Check for program arguments
	args := os.Args
	numArgs := len(args)
	if numArgs != 2 {
		log.Fatal("You must provide the text file name")
	}

	filename := args[1]

	file, err := ioutil.ReadFile(filename)
	check(err)

	output := bytes.Replace(file, []byte("word"), []byte("inserted word"), -1)

	err = ioutil.WriteFile(filename, output, 0666)
	check(err)
	fmt.Println("File has been modified successfully.")
}