golang读写文件之Scan和Fprintf

1. 标准输入输出

os提供了标准输入输出：

    Stdin  = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
    Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
    Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")

func NewFile(fd uintptr, name string) *File

2. Scan

从键盘和标准输入os.Stdin读取输入，最简单的方法是使用fmt包提供的Scan和Sscan开头的函数。

func Scan(a ...interface{}) (n int, err error)
func Scanf(format string, a ...interface{}) (n int, err error)
func Scanln(a ...interface{}) (n int, err error)
func Sscan(str string, a ...interface{}) (n int, err error)
func Sscanf(str string, format string, a ...interface{}) (n int, err error)
func Sscanln(str string, a ...interface{}) (n int, err error)
func Fscan(r io.Reader, a ...interface{}) (n int, err error)
func Fscanf(r io.Reader, format string, a ...interface{}) (n int, err error)
func Fscanln(r io.Reader, a ...interface{}) (n int, err error)

Scanln 扫描来自标准输入的文本，将空格分隔的值依次存放到后续的参数内，直到碰到换行。

Scanf的第一个参数是格式串，其他都相同。

Sscan及开头的函数输入变成了string，Fscan及开头的函数输入变成了io.Reader。

Scan, Fscan, Sscan treat newlines in the input as spaces.

Scanln, Fscanln and Sscanln stop scanning at a newline and require that the items be followed by a newline or EOF.

        fmt.Println("Please enter your full name: ")
        fmt.Scanln(&firstName, &lastName)
        fmt.Printf("Hi %s %s!\n", firstName, lastName)
        fmt.Sscanf("30.0 * 25 * hello", "%f * %d * %s", &f, &i, &s)
        fmt.Println("From the string we read: ", f, i, s)
        fmt.Println("Please enter string: ")
        fmt.Scan(&s)
        fmt.Println(s)

3. Fprintf

printf相关：

func Fprint(w io.Writer, a ...interface{}) (n int, err error)
func Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error)
func Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error)
func Fprintln(w io.Writer, a ...interface{}) (n int, err error)

通过Fprintln()写文件

    const name, age = "Kim",
    n, err := fmt.Fprintln(os.Stdout, name, "is", age, "years old.")

    // The n and err return values from Fprintln are
    // those returned by the underlying io.Writer.
    if err != nil {
        fmt.Fprintf(os.Stderr, "Fprintln: %v\n", err)
    }
或
    for _, v := range d {
        fmt.Fprintln(f, v)
        if err != nil {
            fmt.Println(err)
            return
        }
    }

参考：

1．   https://golang.google.cn/pkg/fmt/#Scanln

2．   https://www.kancloud.cn/kancloud/the-way-to-go/72678

3．   https://studygolang.com/subject/2