go 文件操作 复制和统计字符

复制文件

func CopyFile(dstFileName string,srcFileName string )(written int64,err error)  {
    srcFile,srcErr := os.Open(srcFileName)
    if srcErr != nil{
        fmt.Println("open src file",srcFileName," error :",srcErr)
        return -1,srcErr
    }
    defer srcFile.Close()
    reader := bufio.NewReader(srcFile)
    dstFile,dstErr := os.Open(srcFileName)
    if dstErr != nil{
        fmt.Printf("open dst file %s error,%v\n",dstFileName,err)
        return -1,dstErr
    }
    defer dstFile.Close()
    writer := bufio.NewWriter(dstFile)
    return io.Copy(writer,reader)
}

统计数字和字母的个数 ，主要用到  strs := []rune(str)

func statistics(fileName string)  {
    file,openErr := os.Open(fileName)
    if openErr != nil{
        fmt.Println(openErr)
        return
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    characters := 0
    nums := 0
    others := 0
    for{
        str,err := reader.ReadString('\n')
        if err == io.EOF{
            break
        }
        strs := []rune(str)
        for _,v := range strs{
            switch  {
            case v>='a'&&v<='z':
                fallthrough//穿透
            case v>='A'&&v<='Z':
                characters++
            case v>='0'&&v<='9':
                nums++
            default:
                others++

            }
        }
    }
}