go语言学习笔记----模拟实现文件拷贝函数

原作者: [db:作者] 来自: [db:来源] 收藏邀请

实例1

//main
package main

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

func fileExists(filename string) bool {
	_, err := os.Stat(filename)
	return err == nil || os.IsExist(err)
}

func copyFile(src, dst string) (w int64, err error) {
	srcFile, err := os.Open(src)
	if err != nil {
		fmt.Println(err.Error())
		return
	}

	defer srcFile.Close()
	dstFile, err := os.Create(dst)

	if err != nil {
		fmt.Println(err.Error())
		return
	}

	defer dstFile.Close()

	return io.Copy(dstFile, srcFile)

}
func copyFileAction(src, dst string, showProgress, force bool) {
	if !force {
		if fileExists(dst) {
			fmt.Printf("%s exists override? y/n\n", dst)
			reader := bufio.NewReader(os.Stdin)
			data, _, _ := reader.ReadLine()

			if strings.TrimSpace(string(data)) != "y" {
				return
			}

		}

	}
	copyFile(src, dst)
	if showProgress {
		fmt.Printf("'%s'->'%s'\n", src, dst)
	}
}

func main() {
	var showProgress, force bool
　　　　//定义命令行参数
	flag.BoolVar(&force, "f", false, "force copy when existing")
	flag.BoolVar(&showProgress, "v", false, "explain what is being done")

	flag.Parse()
　　　　//非法命令行数量检测
	if flag.NArg() < 2 {
		flag.Usage()
		return
	}
       //取第0个参数与第一个参数作为源文件名跟目标文件名
	copyFileAction(flag.Arg(0), flag.Arg(1), showProgress, force)
}

示例2：Golang实现文件拷贝功能

package main

import (
    "bufio"
    "fmt"
    "io"
    "os"
)

// 编写一个函数，接收两个文件路径:
func copyFile(dstFileName string, srcFileName string) (written int64, err error) {
    srcFile, err := os.Open(srcFileName)
    if err != nil {
        fmt.Printf("open file error = %v\n", err)
    }
    defer srcFile.Close()

    //通过srcFile，获取到READER
    reader := bufio.NewReader(srcFile)

    //打开dstFileName
    dstFile, err := os.OpenFile(dstFileName, os.O_WRONLY|os.O_CREATE, 0666)
    if err != nil {
        fmt.Printf("open file error = %v\n", err)
        return
    }

    //通过dstFile，获取到WRITER
    writer := bufio.NewWriter(dstFile)
    //writer.Flush()

    defer dstFile.Close()

    return io.Copy(writer, reader)
}


func main() {
    //调用copyFile完成文件拷贝
    srcFile := "e:/copyFileTest02.pdf"
    dstFile := "e:/Go/tools/copyFileTest02.pdf"

    _, err := copyFile(dstFile, srcFile)
    if err == nil {
        fmt.Println("拷贝文件正常...")
    } else {
        fmt.Printf("拷贝文件出错了... err =%v\n", err)
    }
}