Go- 文件读写 -2

package main
import (	"flag"	"fmt"	"os"	"strings")
func printDivider(str ...string) {	fmt.Println()	fmt.Println("-----------------------------------------------")	if len(str) > 0 {		fmt.Println(str)	}}
var NewLine = flag.Bool("n", false, "print newline") // 变量类型 *boolvar HasSpace = flag.Int("s", 1, "print space")       // 变量类型 *int
const (	Space   = " "	Newline = "\n")
func main() {	/*	   读取命令行参数	   命令行参数保存在切片：os.Args[]中，命令行参数按照空格进行分割，索引1开始是参数，索引0是程序名	*/	printDivider("读取命令行参数")	fmt.Printf("Program name: %s\n", os.Args[0])	fmt.Printf("Len of Args: %d\n", len(os.Args))	who := "Marry "	if len(os.Args) > 1 {		who += strings.Join(os.Args[1:], " ")	}	fmt.Println("Hello ", who)
	/*	   命令行解析	   以下代码可使用命令行：	   go run '.\039_Read&WriteFile-2.go' -s 1 Jack Bob	   go run '.\039_Read&WriteFile-2.go' -n Jack Bob	*/	printDivider("命令行解析")	flag.PrintDefaults()	fmt.Println("----------------------")	flag.Parse()
	for i := 0; i < flag.NArg(); i++ {		fmt.Println(flag.Arg(i))	}
	fmt.Printf("NewLine: %t\n", *NewLine)   // 输出：true 或 false	fmt.Printf("HasSpace: %d\n", *HasSpace) // 输出：1	var s string = ""	for i := 0; i < flag.NArg(); i++ {		if i > 0 {			if *NewLine {				s += Newline			} else if *HasSpace == 1 {				s += Space			}		}		s += flag.Arg(i)	}	fmt.Println(s)}

package main
import (	"flag"	"fmt"	"os")
func printDivider(str ...string) {	fmt.Println()	fmt.Println("-----------------------------------------------")	if len(str) > 0 {		fmt.Println(str)	}}
func main() {	/*	   利用切片读写文件	*/	printDivider("利用切片读写文件")	flag.Parse()	if flag.NArg() == 0 {		cat(os.Stdin)	}
	for i := 0; i < flag.NArg(); i++ {		f, err := os.Open(flag.Arg(i))		if f == nil {			fmt.Fprintf(os.Stderr, "cat: can not open file: %s, error: %s\n", flag.Arg(i), err)		}
		cat(f)		f.Close()	}}
func cat(f *os.File) {	const NBUF = 512	var buf [NBUF]byte
	for {		switch nr, err := f.Read(buf[:]); true {		case nr < 0:			fmt.Fprintf(os.Stderr, "cat: error reading: %s\n", err.Error())			os.Exit(1)		case nr == 0:			return		case nr > 0:			if nw, ew := os.Stdout.Write(buf[0:nr]); nw != nr {				fmt.Fprintf(os.Stderr, "cat: error write: %s\n", ew.Error())			}		}	}}