package main import ( "fmt" "os" "io" "log" ) func main() { build_log, err := os.Open("build.log") defer build_log.Close() if err != nil { log.Fatal(err) } out_file, err := os.OpenFile("out.log", os.O_RDWR|os.O_CREATE, 0644) defer out_file.Close() if err != nil { log.Fatal(err) } n, err := io.Copy(out_file, build_log) if err != nil { log.Fatal(err) } fmt.Println("read n bytes", n) }