golang 读取实时追加文件内容

``` package main import ( "flag" "fmt" "io" "os" "runtime" ) import ( "github.com/axgle/mahonia" ) type ReadFile struct { file *os.File gbkFile *mahonia.Reader } func (f *ReadFile) gbkDecode() { decoder := mahonia.NewDecoder("gbk") f.gbkFile = decoder.NewReader(f.file) } func (f *ReadFile) ReadPrint() { var n int var err error data := make([]byte, 1<<16) if runtime.GOOS == "windows" { f.gbkDecode() n, err = f.gbkFile.Read(data) } else { n, err = f.file.Read(data) } switch err { case nil: var lines int out := data indexs := make(map[int]int) for i, d := range out { if d == '\n' { lines++ indexs[lines] = i } } lines += 1 if lines <= line || line <= 0 { fmt.Print(string(data[:n])) } else { index := indexs[lines-line] fmt.Print(string(data[index+1 : n])) } case io.EOF: default: fmt.Println(err) return } } var ( follow bool line int ) func init() { flag.BoolVar(&follow, "f", false, "即时输出文件变化后追加的数据。") flag.IntVar(&line, "n", 10, "output the last K lines, instead of the last 10") } func main() { flag.Parse() var err error var readFile ReadFile if len(os.Args) < 2 { flag.Usage() return } readFile.file, err = os.Open(os.Args[len(os.Args)-1]) if err != nil { fmt.Println(err) return } defer readFile.file.Close() for { readFile.ReadPrint() if !follow { break } } } ```