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, start by installing expo in your project. Then, follow the additional instructions as mentioned by the library's README under "Installation in bare React Native projects" section.
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 { 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);
}
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
Copies a directory.
anyDeletes 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.
null | stringAn md5 hash of the file. Null if the file does not exist or it cannot be read.
null | numberA size of the file in bytes. Null if the file does not exist or it cannot be read.
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.
Retrieves 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.
anyReturns 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.
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.