> For the complete documentation index, see [llms.txt](https://ryanyang.gitbook.io/the-way-to-go-zh-cn/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ryanyang.gitbook.io/the-way-to-go-zh-cn/di-san-bu-fen-go-gao-ji-bian-cheng/12.0/12.3.md).

# 文件拷贝

如何拷贝一个文件到另一个文件？最简单的方式就是使用 io 包：

示例 12.10 [filecopy.go](https://github.com/yangchuansheng/the-way-to-go_ZH_CN/tree/f30ab7d8c58f85840a0afb548024b93642b518d5/eBook/examples/chapter_12/filecopy.go)：

```go
// filecopy.go
package main

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

func main() {
    CopyFile("target.txt", "source.txt")
    fmt.Println("Copy done!")
}

func CopyFile(dstName, srcName string) (written int64, err error) {
    src, err := os.Open(srcName)
    if err != nil {
        return
    }
    defer src.Close()

    dst, err := os.Create(dstName)
    if err != nil {
        return
    }
    defer dst.Close()

    return io.Copy(dst, src)
}
```

注意 `defer` 的使用：当打开目标文件时发生了错误，那么 `defer` 仍然能够确保 `src.Close()` 执行。如果不这么做，文件会一直保持打开状态并占用资源。

## 链接

* [目录](https://github.com/yangchuansheng/the-way-to-go_ZH_CN/tree/f30ab7d8c58f85840a0afb548024b93642b518d5/eBook/directory.md)
* 上一节：[文件读写](/the-way-to-go-zh-cn/di-san-bu-fen-go-gao-ji-bian-cheng/12.0/12.2.md)
* 下一节：[从命令行读取参数](/the-way-to-go-zh-cn/di-san-bu-fen-go-gao-ji-bian-cheng/12.0/12.4.md)