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# 08.13 文件权限

`Unix`系统编程中的一个热门话题是`Unix`文件权限。在本节中，假设你有足够的`Unix`权限，你将学习如何输出任意文件的权限！程序名为`permission.go`，分为三部分。

`permission.go`的第一部分代码如下：

```go
package main

import (
    "fmt"
    "os"
)
```

`permission.go`的第二部分代码如下：

```go
func main() {
    arguments := os.Args
    if len(arguments) == 1 {
        fmt.Printf("usage:permissions filename\n")
        return
    }
```

最后一部分代码如下：

```go
    filename := arguments[1]
    info, _ := os.Stat(filename)
    mode := info.Mode()
    fmt.Println(filename, "mode is", mode.String()[1:10])
}
```

`os.Stat(filename)`调用返回一个大结构体，其中包含了许多数据。因为我们只对文件的权限感兴趣，我们调用`Mode()`方式并打印输出。实际上，我们通过`mode.String()[1:10]`打印了输出的一部分，因为它即是我们感兴趣的那部分。

执行`permission.go`将产生如下输出：

```
$ go run permission.go /tmp/adobegc.log
/tmp/adobegc.log mode is rw-rw-rw-
$ go run permissions.go /dev/random
/dev/random mode is crw-rw-rw
```

`ls(1)`输出可以验证`permission.go`的正确性：

```
$ ls -l /dev/random /tmp/adobegc.log
crw-rw-rw- 1 root wheel 14,   0 Jan 8 20:24 /dev/random
-rw-rw-rw- 1 root wheel  583454 Jan 16 19:12 /tmp/adobegc.log
```


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