import (  // "bufio"  "flag"  "fmt"  "io"  "os" ) import "strconv" var infile *string = flag.String("f", "Null", "please input a file name or dir.") var size *string = flag.String("s", "0", "please input a dst file size.") //func dataCopy(file *os.File, file *os.File) func SplitFile(file *os.File, size int) {  finfo, err := file.Stat()  if err != nil {   fmt.Println("get file info failed:", file, size)  }  fmt.Println(finfo, size)  //每次最多拷贝1m  bufsize := 1024 * 1024  if size < bufsize {   bufsize = size  }  buf := make([]byte, bufsize)  num := (int(finfo.Size()) + size - 1) / size  fmt.Println(num, len(buf))  for i := 0; i < num; i++ {   copylen := 0   newfilename := finfo.Name() + strconv.Itoa(i)   newfile, err1 := os.Create(newfilename)   if err1 != nil {    fmt.Println("failed to create file", newfilename)   } else {    fmt.Println("create file:", newfilename)   }   for copylen < size {    n, err2 := file.Read(buf)    if err2 != nil && err2 != io.EOF {     fmt.Println(err2, "failed to read from:", file)     break    }    if n <= 0 {     break    }    //fmt.Println(n, len(buf))    //写文件    w_buf := buf[:n]    newfile.Write(w_buf)    copylen += n   }  }  return } func main() {  flag.Parse()  if *infile == "Null" {   fmt.Println("no file to input")   return  }  file, err := os.Open(*infile)  if err != nil {   fmt.Println("failed to open:", *infile)  }  defer file.Close()  size, _ := strconv.Atoi(*size)  SplitFile(file, size*1024) }