package main import ( "bytes" "fmt" "io/ioutil" "os" ) func main() { args := os.Args if len(args) != 4 { fmt.Println("gogoreplace wants three arguments") fmt.Println(" gogoreplace oldsubstring newsubstring filename") os.Exit(1) } data, err := ioutil.ReadFile(args[3]) if err != nil { panic(err) } data = bytes.Replace(data, []byte(args[1]), []byte(args[2]), -1) if err := ioutil.WriteFile(args[3], data, 0666); err != nil { panic(err) } }