18.7 文件

（1）如何打开一个文件并读取：

  1. file, err := os.Open("input.dat")
  2.   if err != nil {
  3.     fmt.Printf("An error occurred on opening the inputfile\n" +
  4.       "Does the file exist?\n" +
  5.       "Have you got acces to it?\n")
  6.     return
  7.   }
  8.   defer file.Close()
  9.   iReader := bufio.NewReader(file)
  10.   for {
  11.     str, err := iReader.ReadString('\n')
  12.     if err != nil {
  13.       return // error or EOF
  14.     }
  15.     fmt.Printf("The input was: %s", str)
  16.   }

（2）如何通过切片读写文件：

  1. func cat(f *file.File) {
  2.   const NBUF = 512
  3.   var buf [NBUF]byte
  4.   for {
  5.     switch nr, er := f.Read(buf[:]); true {
  6.     case nr < 0:
  7.       fmt.Fprintf(os.Stderr, "cat: error reading from %s: %s\n",
  8.         f.String(), er.String())
  9.       os.Exit(1)
  10.     case nr == 0: // EOF
  11.       return
  12.     case nr > 0:
  13.       if nw, ew := file.Stdout.Write(buf[0:nr]); nw != nr {
  14.         fmt.Fprintf(os.Stderr, "cat: error writing from %s: %s\n",
  15.           f.String(), ew.String())
  16.       }
  17.     }
  18.   }
  19. }

链接