golang中的文件读写

忘是亡心i 2022-03-16 08:42 272阅读 0赞

### 读取文件全部内容 ###

package main
    
    import (
        "fmt"
        "os"
        "io/ioutil"
    )
    
    func main() {
        f, err := os.Open("input.txt")
        if err != nil {
            fmt.Println("os Open error: ", err)
            return
        }
        defer f.Close()
    
        //读取文件全部内容
        b, err := ioutil.ReadAll(f)
        if err != nil {
            fmt.Println("ioutil ReadAll error: ", err)
            return
        }
    
        fmt.Println("content: ", string(b))
    }

package main
    
    import (
        "fmt"
        "io/ioutil"
    )
    
    func main() {
        //读取文件全部内容
        b, err := ioutil.ReadFile("input.txt")
        if err != nil {
            fmt.Println("ioutil ReadFile error: ", err)
            return
        }
    
        fmt.Println("content: ", string(b))
    }

### 使用ioutil.WriteFile写入文件 ###

func WriteFile(filename string, data []byte, perm os.FileMode) error

WriteFile将data写入到filename指定的文件中。如果文件不存在，WriteFile将会创建该文件，且文件的权限是perm；如果文件存在，先清空文件内容再写入。

package main
    
    import (
        "io/ioutil"
        "fmt"
    )
    
    func main() {
        content := []byte("hello golang")
        //将指定内容写入到文件中
        err := ioutil.WriteFile("output.txt", content, 0666)
        if err != nil {
            fmt.Println("ioutil WriteFile error: ", err)
        }
    }

### 获取文件信息 ###

package main
    
    import (
        "fmt"
        "os"
    )
    
    func main() {
        f, err := os.Open("input.txt")
        if err != nil {
            fmt.Println("os Open error: ", err)
            return
        }
        defer f.Close()
    
        stat, err := f.Stat()
        if err != nil {
            fmt.Println("f Stat error: ", err)
        }
    
        fmt.Println("name: ", stat.Name())
        fmt.Println("size: ", stat.Size())
    }

运行结果

name: input.txt
    size: 18

### 按行读取文件 ###

package main
    
    import (
        "fmt"
        "os"
        "bufio"
        "io"
    )
    
    func main() {
        f, err := os.Open("input.txt")
        if err != nil {
            fmt.Println("os Open error: ", err)
            return
        }
        defer f.Close()
    
        br := bufio.NewReader(f)
        for {
            line, _, err := br.ReadLine()
            if err == io.EOF {
                break
            } else if err != nil {
                fmt.Println("br ReadLine error: ", err)
                return
            }
    
            fmt.Println("line: ", string(line))
        }
    }

### 按行写入文件 ###

`os.Open("filename")`，这个函数的原理其实是这样的`OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)`，O\_RDWR也就是说用读写的权限，O\_CREATE然后文件存在忽略，不存在创建它，O\_TRUNC文件存在截取长度为0

package main
    
    import (
        "fmt"
        "os"
        "bufio"
    )
    
    func main() {
        f, err := os.Create("output.txt")
        if err != nil {
            fmt.Println("os Create error: ", err)
            return
        }
        defer f.Close()
    
        content := map[string]string{
            "hello": "111",
            "world": "222",
        }
        bw := bufio.NewWriter(f)
        for k, v := range content {
            bw.WriteString(k + ":" + v + "\n")
        }
        bw.Flush()
    }

### 追加文件内容 ###

package main
    
    import (
        "fmt"
        "os"
    )
    
    func main() {
        f, err := os.OpenFile("output.txt", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0777)
        if err != nil {
            fmt.Println("os OpenFile error: ", err)
            return
        }
        defer f.Close()
    
        f.WriteString("another content")
    }

### 按字节读取文件内容 ###

package main
    
    import (
        "fmt"
        "os"
        "io"
    )
    
    func main() {
        f, err := os.Open("input.txt")
        if err != nil {
            fmt.Println("os Open error: ", err)
            return
        }
        defer f.Close()
    
        for {
            b := make([]byte, 4)
            n, err := f.Read(b)//读取至多4个字节的内容
            if err == io.EOF {
                break
            } else if err != nil {
                fmt.Println("f Read error: ", err)
                return
            }
            b = b[:n]
    
            fmt.Printf("read length=%d, content=%s\n", n, string(b))
        }
    }

运行结果

read length=4, content=1234
    read length=4, content=5678
    read length=2, content=90

## 参考 ##

*  [Go语言学习之ioutil包(The way to go)][Go_ioutil_The way to go]
 *  [Go实战–golang中读写文件的几种方式][Go_golang]
 *  [https://golang.org/pkg/io/ioutil/][https_golang.org_pkg_io_ioutil]
 *  [golang 逐行读取文件][golang]
 *  [golang按行写文件][golang 1]
 *  [golang标准库的分析os包（6）][golang_os_6]
 *  [Go by Example: Reading Files][Go by Example_ Reading Files]

[Go_ioutil_The way to go]: https://blog.csdn.net/wangshubo1989/article/details/69395568
[Go_golang]: https://blog.csdn.net/wangshubo1989/article/details/74777112
[https_golang.org_pkg_io_ioutil]: https://golang.org/pkg/io/ioutil/
[golang]: http://www.cnblogs.com/rojas/p/4395866.html
[golang 1]: https://blog.csdn.net/xielingyun/article/details/49992099
[golang_os_6]: https://segmentfault.com/a/1190000000376807
[Go by Example_ Reading Files]: https://gobyexample.com/reading-files