File Management Development

What if I failed to open the URI returned by picker with the read/write permissions? (API version 10)

Symptom

When fs.openSync() with mode set to OpenMode.READ_WRITE is called to open a URI returned by a picker API, the file cannot be opened.

Cause Analysis

The permission on the URI obtained by picker is write-only. As a result, you cannot open the file in read/write mode.

Solution

Currently, you can open the file URI in write-only mode.

fs.openSync(uri, fs.OpenMode.WRITE_ONLY)

In later versions, when a file is opened or saved by using a picker API, the URI returned will be granted with the read/write permissions. You can open and edit the file as required.

How do I obtain the path of system screenshots? (API version 9)

Solution

The screenshots are stored in /storage/media/100/local/files/Pictures/Screenshots/.

How do I change the permissions on a directory to read/write? (API 9)

Symptom

When the hdc command is used to send a file to a device, "permission denied" is displayed.

Solution

Run the hdc shell mount -o remount,rw / command to grant the read/write permissions.

What is the best way to create a file if the file to open does not exist? (API version 9)

Solution

Use fs.open(path: string, mode?: number) with mode set to fs.OpenMode.CREATE.

How do I solve the problem of garbled Chinese characters in a file? (API version 9)

Solution

After the buffer data of the file is read, use TextDecoder of @ohos.util to decode the file content.

let filePath = getContext(this).filesDir + "/test0.txt";
let stream = fs.createStreamSync(filePath, "r+");
let buffer = new ArrayBuffer(4096)
let readOut = stream.readSync(buffer);
let textDecoder = util.TextDecoder.create('utf-8', { ignoreBOM: true })
let readString = textDecoder.decodeWithStream(new Uint8Array(buffer), { stream: false });
console.log ("File content read: "+ readString);

Why is an error reported when fs.copyFile is used to copy a datashare:// file opened by fs.open? (API version 9)

Solution

fs.copyFile does not support URIs. You can use fs.open() to obtain the URI, obtain the file descriptor (FD) based on the URI, and then use fs.copyFile to copy the file based on the FD.

let file = fs.openSync("datashare://...")
fs.copyFile(file.fd, 'dstPath', 0).then(() => {
  console.info('copyFile success')
}).catch((err) => {
  console.info("copy file failed with error message: " + err.message + ", error code: " + err.code);
})

How do I modify the content of a JSON file in a sandbox directory? (API version 9)

Solution

Perform the following steps:

Use fs.openSyn to obtain the FD of the JSON file.

import fs from '@ohos.file.fs';  
let sanFile = fs.open(basePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
let fd = sanFile.fd;

Use fs.readSync to read the file content.
```
let content = fs.readSync(basePath);
```
Modify the file content.
```
obj.name = 'new name';
```
Use fs.writeSync to write the data to the JSON file.
```
fs.writeSync(file.fd, JSON.stringify(obj));
```

For more information, see @ohos.file.fs.

What is the real path corresponding to the file path obtained through the fileAccess module? (API version 9)

Applicable to: stage model

Solution

The files are stored in the /storage/media/100/local/files directory. The specific file path varies with the file type and source. To obtain the file path based on the file name, run the following command in the /storage/media/100/local/files directory:
-name [filename]

References

For more information, see Uploading and Downloading an Application File.

How do I listen for the changes of a file or folder? (API version 10)

Solution

You can use fs.createWatcher to listen for the changes of a file or folder with the registered callback.

References

@ohos.file.fs