Expo FileSystem (next)A library that provides access to the local file system on the device.
Thenextversion of the FileSystem API is included in theexpo-file-systemlibrary. It can be used alongside the previous API, and offers a simplified, object oriented way of performing filesystem operations.
expo-file-system/next provides access to the file system stored locally on the device. It can also download files from the network.
To provide quicker updates,expo-file-system/nextis currently unsupported in Expo Go and Snack. To use it, create a development build.
Installation
-Â npx expo install expo-file-systemIf you are installing this in an existing React Native app, make sure to install expo in your project.
Usage
Writing and reading text files
import { File, Paths } from 'expo-file-system/next';
try {
const file = new File(Paths.cache, 'example.txt');
file.create(); // can throw an error if the file already exists or no permission to create it
file.write('Hello, world!');
console.log(file.text()); // Hello, world!
} catch (error) {
console.error(error);
}
Downloading files
import { File, Paths } from 'expo-file-system/next';
const url = 'https://pdfobject.com/pdf/sample.pdf';
const destination = new Directory(Paths.cache, 'pdfs');
try {
destination.create();
const output = await File.downloadFileAsync(url, destination);
console.log(output.exists); // true
console.log(output.uri); // path to the downloaded file, e.g. '${cacheDirectory}/pdfs/sample.pdf'
} catch (error) {
console.error(error);
}
Moving and copying files
import { File, Paths } from 'expo-file-system/next';
try {
const file = new File(Paths.document, 'example.txt');
file.create();
console.log(file.uri); // '${documentDirectory}/example.txt'
file.move(Paths.cache);
console.log(file.uri); // '${cacheDirectory}/example.txt'
file.move(new Directory(Paths.cache, 'newFolder'));
console.log(file.uri); // '${cacheDirectory}/newFolder/example.txt'
} catch (error) {
console.error(error);
}
Using legacy FileSystem API
import * as FileSystem from 'expo-file-system';
import { File, Paths } from 'expo-file-system/next';
try {
const file = new File(Paths.cache, 'example.txt');
const content = await FileSystem.readAsStringAsync(file.uri);
console.log(content);
} catch (error) {
console.error(error);
}
Listing directory contents recursively
import { Directory, Paths } from 'expo-file-system/next';
function printDirectory(directory: Directory, indent: number = 0) {
console.log(`${' '.repeat(indent)} + ${directory.name}`);
const contents = directory.list();
for (const item of contents) {
if (item instanceof Directory) {
printDirectory(item, indent + 2);
} else {
console.log(`${' '.repeat(indent + 2)} - ${item.name} (${item.size} bytes)`);
}
}
}
try {
printDirectory(new Directory(Paths.cache));
} catch (error) {
console.error(error);
}
Uploading files using expo/fetch
You can upload files as blobs directly with fetch built into the Expo package:
import { fetch } from 'expo/fetch';
import { File } from 'expo-file-system/next';
const src = new File(testDirectory, 'file.txt');
file.write('Hello, world!');
const blob = src.blob();
const response = await fetch('https://example.com', {
method: 'POST',
body: blob,
});
Or using the FormData constructor:
import { fetch } from 'expo/fetch';
const src = new File(testDirectory, 'file.txt');
file.write('Hello, world!');
const blob = src.blob();
const formData = new FormData();
formData.append('data', blob);
const response = await fetch('https://example.com', {
method: 'POST',
body: formData,
});
API
Classes
Type: Class extends FileSystemDirectory
Represents a directory on the filesystem.
A Directory instance can be created for any path, and does not need to exist on the filesystem during creation.
Directory Properties
booleanA boolean representing if a directory exists. true if the directory exists, false otherwise.
Also, false if the application does not have read access to the file.
stringRepresents the directory URI. The field is read-only, but it may change as a result of calling some methods such as move.
Directory Methods
| Parameter | Type |
|---|---|
| options(optional) | CreateOptions |
Creates a directory that the current uri points to.
voidDeletes a directory. Also deletes all files and directories inside the directory.
voidType: Class extends FileSystemFile
File Properties
booleanA boolean representing if a file exists. true if the file exists, false otherwise.
Also, false if the application does not have read access to the file.
A md5 hash of the file. Null if the file does not exist, or it cannot be read.
Acceptable values are: null | string
A size of the file in bytes. Null if the file does not exist, or it cannot be read.
Acceptable values are: null | number
A mime type of the file. Null if the file does not exist, or it cannot be read.
Acceptable values are: null | string
stringRepresents the file URI. The field is read-only, but it may change as a result of calling some methods such as move.
File Methods
Retrieves content of the file as base64.
stringThe contents of the file as a base64 string.
Returns the file as a Blob. The blob can be used in @expo/fetch to send files over network and for other uses.
BlobRetrieves byte content of the entire file.
Uint8ArrayThe contents of the file as a Uint8Array.
| Parameter | Type | Description |
|---|---|---|
| url | string | The URL of the file to download. |
| destination | Directory | File | The destination directory or file. If a directory is provided, the resulting filename will be determined based on the response headers. |
Moves a directory. Updates the uri property that now points to the new location.
voidReturns a FileHandle object that can be used to read and write data to the file.
FileHandleReadableStream<Uint8Array>WritableStream<Uint8Array>| Parameter | Type | Description |
|---|---|---|
| content | string | Uint8Array | The content to write into the file. |
Writes content to the file.
voidFileHandle Properties
A property that indicates the current byte offset in the file. Calling readBytes or writeBytes will read or write a specified amount of bytes starting from this offset. The offset is incremented by the number of bytes read or written.
The offset can be set to any value within the file size. If the offset is set to a value greater than the file size, the next write operation will append data to the end of the file.
Null if the file handle is closed.
Acceptable values are: null | number
FileHandle Methods
Closes the file handle. This allows the file to be deleted, moved or read by a different process. Subsequent calls to readBytes or writeBytes will throw an error.
void| Parameter | Type | Description |
|---|---|---|
| length | number | The number of bytes to read. |
Reads the specified amount of bytes from the file at the current offset.
Uint8Array| Parameter | Type | Description |
|---|---|---|
| bytes | Uint8Array | A |
Writes the specified bytes to the file at the current offset.
voidType: Class extends PathUtilities
Paths Properties
Record<string, Directory>DirectoryA property containing the cache directory – a place to store files that can be deleted by the system when the device runs low on storage.
DirectoryA property containing the document directory – a place to store files that are safe from being deleted by the system.
Paths Methods
| Parameter | Type | Description |
|---|---|---|
| path | string | File | Directory | The path to get the base name from. |
| ext(optional) | string | An optional file extension. |
Returns the base name of a path.
stringA string representing the base name.
Returns the directory name of a path.
stringA string representing the directory name.
Returns the extension of a path.
stringA string representing the extension.
Checks if a path is absolute.
booleantrue if the path is absolute, false otherwise.
Joins path segments into a single path.
stringA string representing the joined path.
Normalizes a path.
stringA string representing the normalized path.
Parses a path into its components.
{
base: string,
dir: string,
ext: string,
name: string,
root: string
}An object containing the parsed path components.