go 基本IO接口

package main

import (
        "fmt"
        "io"
        "strings"
)

func ReadFrom(reader io.Reader, num int) ([]byte, error) {
        p := make([]byte, num)
        n, err := reader.Read(p)
        if n > 0 {
                return p[:n], nil
        }
        return p, err
}

func sampleReaderFromString() {
        data, _ := ReadFrom(strings.NewReader("from string"), 12)
        fmt.Println(data)
}

func main() {
        sampleReaderFromString()
}

　　输出：

[102 114 111 109 32 115 116 114 105 110 103]

package main

import (
        "fmt"
        "io"
        "os"
        "strings"
)

func sampleReadFile() {
        file, _ := os.Open("main.go")
        defer file.Close()

        data, _ := ReadFrom(file, 20)
        fmt.Println(string(data))
}
func ReadFrom(reader io.Reader, num int) ([]byte, error) {
        p := make([]byte, num)
        n, err := reader.Read(p)
        if n > 0 {
                return p[:n], nil
        }
        return p, err
}
func sampleReadStdin() {
        fmt.Println("please input from stdin:")
        data, _ := ReadFrom(os.Stdin, 11)
        fmt.Println(data)
}
func sampleReaderFromString() {
        data, _ := ReadFrom(strings.NewReader("from string"), 12)
        fmt.Println(data)
}

func main() {
        //sampleReaderFromString()
        //ampleReadStdin()
        sampleReadFile()
}

输出：

package main

import