# 获取并使用公共目录

## 通过 ArkTS 接口获取并访问公共目录

目录环境能力接口（[ohos.file.environment](../reference/apis-core-file-kit/js-apis-file-environment.md)）提供获取公共目录路径的能力，支持三方应用在公共文件用户目录下进行文件访问操作。

 **约束限制**
 - 使用此方式，需确认设备具有以下系统能力：SystemCapability.FileManagement.File.Environment.FolderObtain，当前仅支持2in1设备。
   ```ts
   if (!canIUse('SystemCapability.FileManagement.File.Environment.FolderObtain')) {
       console.error('this api is not supported on this device');
       return;
   }
   ```
 - 公共目录获取接口仅用于获取公共目录路径，不对公共目录访问权限进行校验。若需访问公共目录需申请对应的公共目录访问权限。三方应用需要访问公共目录时，需通过弹窗授权向用户申请授予 Download 目录权限、Documents 目录权限或 Desktop 目录权限，具体参考[访问控制-向用户申请授权](../security/AccessToken/request-user-authorization.md)。
   <!--RP1-->
   ```json
   "requestPermissions" : [
       "ohos.permission.READ_WRITE_DOWNLOAD_DIRECTORY",
       "ohos.permission.READ_WRITE_DOCUMENTS_DIRECTORY",
       "ohos.permission.READ_WRITE_DESKTOP_DIRECTORY",
   ]
   ```
   <!--RP1End-->

### 示例

1. 获取公共目录路径。

   ```ts
    import { BusinessError } from '@kit.BasicServicesKit';
    import { Environment } from '@kit.CoreFileKit';

    function getUserDirExample() {
        try {
            const downloadPath = Environment.getUserDownloadDir();
            console.info(`success to getUserDownloadDir: ${downloadPath}`);
            const documentsPath = Environment.getUserDocumentDir();
            console.info(`success to getUserDocumentDir: ${documentsPath}`);
        } catch (error) {
            const err: BusinessError = error as BusinessError;
            console.error(`failed to get user dir, because: ${JSON.stringify(err)}`);
        }
    }
   ```

2. 以 Download 目录为例，访问 Download 目录下的文件。

   ```ts
    import { BusinessError } from '@kit.BasicServicesKit';
    import { Environment } from '@kit.CoreFileKit';
    import { fileIo as fs } from '@kit.CoreFileKit';
    import { common } from '@kit.AbilityKit';

    function readUserDownloadDirExample() {
        // 检查是否具有 READ_WRITE_DOWNLOAD_DIRECTORY 权限，无权限则需要向用户申请授予权限。
        try {
            // 获取 Download 目录
            const downloadPath = Environment.getUserDownloadDir();
            console.info(`success to getUserDownloadDir: ${downloadPath}`);
            const context = getContext() as common.UIAbilityContext;
            const dirPath = context.filesDir;
            console.info(`success to get filesDir: ${dirPath}`);
            // 查看 Download 目录下的文件并拷贝到沙箱目录中
            let fileList: string[] = fs.listFileSync(downloadPath);
            fileList.forEach((file, index) => {
                console.info(`${downloadPath} ${index}: ${file}`);
                fs.copyFileSync(`${downloadPath}/${file}`, `${dirPath}/${file}`);
            });
            // 查看沙箱目录下对应的文件
            fileList = fs.listFileSync(dirPath);
            fileList.forEach((file, index) => {
                console.info(`${dirPath} ${index}: ${file}`);
            });
        } catch (error) {
            const err: BusinessError = error as BusinessError;
            console.error(`Error code: ${err.code}, message: ${err.message}`);
        }
    }
   ```

3. 以 Download 目录为例，保存文件到 Download 目录。

   ```ts
    import { BusinessError } from '@kit.BasicServicesKit';
    import { Environment } from '@kit.CoreFileKit';
    import { fileIo as fs } from '@kit.CoreFileKit';

    function writeUserDownloadDirExample() {
    // 检查是否具有 READ_WRITE_DOWNLOAD_DIRECTORY 权限，无权限则需要向用户申请授予权限。
        try {
            // 获取 Download 目录
            const downloadPath = Environment.getUserDownloadDir();
            console.info(`success to getUserDownloadDir: ${downloadPath}`);
            // 保存 temp.txt 到 Download 目录下
            const file = fs.openSync(`${downloadPath}/temp.txt`, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);
            fs.writeSync(file.fd, 'write a message');
            fs.closeSync(file);
        } catch (error) {
            const err: BusinessError = error as BusinessError;
            console.error(`Error code: ${err.code}, message: ${err.message}`);
        }
    }
   ```



## 通过 C/C++ 接口获取并使用公共目录

除了通过 ArkTS 访问公共目录的方式，也可通过 C/C++ 接口进行目录访问，具体可以参考 [Environment](../reference/apis-core-file-kit/_environment.md)。

 **约束限制**
 - 使用此接口，需确认设备具有以下系统能力：SystemCapability.FileManagement.File.Environment.FolderObtain。
 - 三方应用需要访问公共目录时，需通过弹窗授权向用户申请授予 Download 目录权限、Documents 目录权限或 Desktop 目录权限，具体参考[访问控制-向用户申请授权](../security/AccessToken/request-user-authorization.md)。

### 接口说明

接口的详细说明，请参考[API参考](../reference/apis-core-file-kit/_environment.md)

| 接口名称                                                                 | 描述                           |
| ------------------------------------------------------------------------ | ------------------------------ |
| FileManagement_ErrCode OH_Environment_GetUserDownloadDir (char **result) | 获取用户Download目录沙箱路径。只支持2in1设备 |
| FileManagement_ErrCode OH_Environment_GetUserDesktopDir (char **result)  | 获取用户Desktop目录沙箱路径。只支持2in1设备  |
| FileManagement_ErrCode OH_Environment_GetUserDocumentDir (char **result) | 获取用户Document目录沙箱路径。只支持2in1设备 |

### 开发步骤

**在CMake脚本中链接动态库**

CMakeLists.txt中添加以下lib。

```txt
target_link_libraries(sample PUBLIC libohenvironment.so libhilog_ndk.z.so)
```

**添加头文件**

```c++
#include <filemanagement/environment/oh_environment.h>
#include <filemanagement/fileio/oh_fileio.h>
#include <hilog/log.h>
```

1. 调用 OH_Environment_GetUserDownloadDir 接口获取用户 Download 目录沙箱路径，在接口中使用malloc申请的内存需要在使用完后释放因此需要free对应的内存。示例代码如下所示：

    ```c++
    void GetUserDownloadDirExample()
    {
        char *downloadPath = nullptr;
        FileManagement_ErrCode ret = OH_Environment_GetUserDownloadDir(&downloadPath);
        if (ret == 0) {
            OH_LOG_INFO(LOG_APP, "Download Path=%{public}s", downloadPath);
            free(downloadPath);
        } else {
            OH_LOG_ERROR(LOG_APP, "GetDownloadPath fail, error code is %{public}d", ret);
        }
    }
    ```

2. 调用 OH_Environment_GetUserDownloadDir 接口获取用户 Download 目录沙箱路径，并查看 Download 目录下的文件。示例代码如下所示：

    ```c++
    void ScanUserDownloadDirPathExample()
    {
        // 获取 download 路径
        char *downloadPath = nullptr;
        FileManagement_ErrCode ret = OH_Environment_GetUserDownloadDir(&downloadPath);
        if (ret == 0) {
            OH_LOG_INFO(LOG_APP, "Download Path=%{public}s", downloadPath);
        } else {
            OH_LOG_ERROR(LOG_APP, "GetDownloadPath fail, error code is %{public}d", ret);
            return;
        }
        // 查看文件夹下的文件
        struct dirent **namelist = {nullptr};
        int num = scandir(downloadPath, &namelist, nullptr, nullptr);
        if (num < 0) {
            free(downloadPath);
            OH_LOG_ERROR(LOG_APP, "Failed to scan dir");
            return;
        }
        for (int i = 0; i < num; i++) {
            OH_LOG_INFO(LOG_APP, "%{public}s", namelist[i]->d_name);
        }
        free(downloadPath);
        free(namelist);
    }
    ```

3. 调用 OH_Environment_GetUserDownloadDir 接口获取用户 Download 目录沙箱路径，并保存 temp.txt 到 Download 目录下。示例代码如下所示：

    ```c++
    void WriteUserDownloadDirPathExample()
    {
        // 获取 download 路径
        char *downloadPath = nullptr;
        FileManagement_ErrCode ret = OH_Environment_GetUserDownloadDir(&downloadPath);
        if (ret == 0) {
            OH_LOG_INFO(LOG_APP, "Download Path=%{public}s", downloadPath);
        } else {
            OH_LOG_ERROR(LOG_APP, "GetDownloadPath fail, error code is %{public}d", ret);
            return;
        }
        // 保存文件到 download 目录下
        std::string filePath = std::string(downloadPath) + "/temp.txt";
        free(downloadPath);

        std::ofstream outfile;
        outfile.open(filePath.c_str());
        if (!outfile) {
            OH_LOG_ERROR(LOG_APP, "Failed to open file");
            return;
        }
        std::string msg = "Write a message";
        outfile.write(msg.c_str(), sizeof(msg));
        outfile.close();
    }
    ```