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@amazon-devices/kepler-file-system

Open Beta Documentation Amazon offers this technical documentation as part of a pre-release, open beta. The features described might change as Amazon receives feedback and iterates on the features. For the most current feature information, see the Release Notes.

The Kepler File System API provides support to Kepler by enabling file system querying, traversing, reading, and writing operations.

Remarks

Apps operate in a sandboxed environment with a restricted view of the device file system. Kepler makes the following app-specific directories available in the sandbox.

Path	Writeable	Description
`/pkg`	No	The root of the app package.
`/pkg/assets`	No	Assets installed by the package.
`/pkg/lib`	No	App entry point component and any additional libraries installed by the package.
`/data`	Yes	Writable location for the app data. Persistent across device reboots and package upgrades, not shared between apps or services. This directory isn't persistent on app uninstall.
`/tmp`	Yes	Each app gets its own temporary storage, which cannot be shared with any other apps or services. Non-persistent, will be removed during device reboot.
`/proc`	No	Only `/proc/self` is available to the app.

Get started

Setup

Add the following library dependency to the dependencies section of your package.json file.
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```
 "@amazon-devices/kepler-file-system": "~0.0.1"
```
Regenerate the package-lock.json file using the npm install command.

Usage

The following examples use async/await to handle Promises returned by FileSystem methods. This pattern provides a cleaner way to work with asynchronous operations.

Open a file

This example uses async/await to handle the Promise returned by FileSystem.openFile().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleOpenFile = async () => {
  FileSystem.openFile('/data/fileSystemTestFile', 0)
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Remove a file

This example uses async/await to handle the Promise returned by FileSystem.removeFile().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleRemoveFile = async () => {
  FileSystem.removeFile('/data/fileSystemTestFile')
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Remove a directory

This example uses async/await to handle the Promise returned by FileSystem.removeDir().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleRemoveDir = async () => {
  FileSystem.removeDir('/data')
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Remove a directory recursively

This example uses async/await to handle the Promise returned by FileSystem.removeDirAll().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleRemoveDirAll = async () => {
  FileSystem.removeDirAll('/data')
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Read a file as a string

This example uses async/await to handle the Promise returned by FileSystem.readFileAsString().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleReadFileAsString = async () => {
  FileSystem.readFileAsString('/data/fileToReadWrite', 'UTF-8')
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Write a string to a file

This example uses async/await to handle the Promise returned by FileSystem.writeStringToFile().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleWriteStringToFile = async () => {
  FileSystem.writeStringToFile('/data/fileToReadWrite', 'Hello world!', 'UTF-8')
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Access file metadata

This example uses async/await to handle the Promise returned by FileSystem.getMetadata().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

export const handleGetMetadata = async () => {
  FileSystem.getMetadata('/data/fileSystemTestFile', false)
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

Access directory entries

This example uses async/await to handle the Promise returned by FileSystem.getEntries().

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import { KeplerFileSystem as FileSystem } from '@amazon-devices/kepler-file-system';

const handleGetEntries = async () => {
  FileSystem.getEntries('/data')
    .then((response: any) => console.log(response))
    .catch((error: any) => console.error(error));
};

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Last updated: Sep 30, 2025