Read/Write Files (Non-RDF Resources)

Solid Pods can store regular files (e.g., PDFs, photos, etc.) in addition to storing structured data as Things and SolidDatasets (see Read/Write Structured Data to store structured data).

The solid-client library provides various file handling functions. Like other data stored in a Solid Pod, each File [1] is a Resource with a distinct URL, which may or may not include the file extension, (e.g., .jpg extension for an image file).

Required Access

Note

Inrupt also supports access requests and grants. For details, see Access Requests and Grants.

The same access control mechanism applies to these files as applies to any other Resource in the Pod. As such, to perform file operations on restricted Resources (i.e., not open to the general public), the user must first authenticate as someone with the appropriate access. Then, to make authenticated requests, pass to the various read/write functions the authenticated Session’s fetch function. For more information on authentication, see Authentication.

Action	Required Access
Read a file.	Read access to the file.
To write a new file to a Container.	Either Append or Write access to the Container, depending on the library function used: To use saveFileInContainer(), the user must have Append and/or Write access to the Container. To use overwriteFile(), the user must have both Write access to the Container and Write access to the target file. Tip To create access policies for yet to be created files, create a default member policy with Write access for the Container.
To replace an existing file in a container.	Either Append or Write access to the Container, depending on the library function used: To use saveFileInContainer(), the user must have Append and/or Write access to the Container. To use overwriteFile(), the user must have both Write access to the Container and Write access to the target File.
To delete an existing file in a Container.	Both Write access to the File and Write access to the Container.

Pod URL

For files saved in a Pod, their URL acts as the unique identifier. Their URLs are relative to the Pod’s URL. For example:

• https://storage.inrupt.com/{someIdentifier}/pictures/picture.jpg

• https://storage.inrupt.com/{someIdentifier}/data/inventory1.pdf

where https://storage.inrupt.com/{someIdentifier}/ is the Pod’s URL.

Inrupt’s solid-client library provides getPodUrlAll to get the Pod’s URL or if the user has multiple Pods, the list of Pod URLs.

import { getPodUrlAll } from "@inrupt/solid-client";

// Returns a list of URLs

const mypods = await getPodUrlAll(webID, { fetch: fetch });

Retrieve a File

Note

Inrupt also supports access requests and grants. For details, see Access Requests and Grants.

To read a file, you can use getFile() to fetch the file content at the specified URL. The getFile() returns a File. [1] Once fetched, you can decode appropriately.

Note

To use getFile(), the user must have Read access for the file. For more information on user access, see Access Policies: Universal API.

The following example uses getFile() to read the specified files. The example assumes the user has the appropriate access.

BrowserNode.JS

// ... import statement for authentication, which includes the fetch function, is omitted for brevity.
import { getFile, isRawData, getContentType, getSourceUrl, } from "@inrupt/solid-client";

// ... Various logic, including login logic, omitted for brevity.

// Read file from Pod 
async function readFileFromPod(fileURL) {
  try {
    // File (https://docs.inrupt.com/developer-tools/api/javascript/solid-client/modules/interfaces.html#file) is a Blob (see https://developer.mozilla.org/docs/Web/API/Blob)
    const file = await getFile(
      fileURL,               // File in Pod to Read
      { fetch: fetch }       // fetch from authenticated session
    );

    console.log( `Fetched a ${getContentType(file)} file from ${getSourceUrl(file)}.`);
    console.log(`The file is ${isRawData(file) ? "not " : ""}a dataset.`);

  } catch (err) {
    console.log(err);
  }
}

The above example uses:

• getFile() to fetch the File. [1]

• getContentType() to return the content type; for example, text/plain;charset=UTF-8 or image/svg+xml or text/html;charset=UTF-8. You can use getContentType() on any Resource, not just files.

• isRawData() to determine if the Resource is raw data (i.e., not a SolidDataset). You can use isRawData() on any Resource, not just files.

Note

You can use getFile() to retrieve a file that contains structured data. In this case, getContentType() on the returned File [1] might return text/turtle; charset=UTF-8 if the user’s Pod server defaults to returning structured data in that format. The isRawData() on the File returns false.

Write a File

When writing a file to a Pod, you can:

• Use overwriteFile() to specify the exact destination file URL.

• Use saveFileInContainer() to specify only the URL for the parent Container.

Write a File to a Specific URL

To specify the file’s destination URL during the save, use overwriteFile(). To use overwriteFile(), pass it the following parameters:

File URL	The destination URL for the File. If a file already exists at that URL, the function overwrites the existing file.
Options object	An object that includes the following options: { contentType: <MIME type>, fetch: <fetch func> } fetch fetch function from an authenticated session if accessing restricted Resource (i.e., the general public cannot write file at the specified location). See Authentication. Optional if the general public can write files at the specified location. contentType Optional. MIME type.

Note

• To use overwriteFile(), the user must have both Write access to the Container and Write access to the target file. Since the new file does not yet exist in the Container, the Container must have included Write access as its default member access. For more information on user access, see Access Policies: Universal API.

• When using overwriteFile() to save the file to the destination URL, the Solid server creates any intermediate Container as needed.

BrowserNode.JS

The following example uses overwriteFile() to save the selected local files to the specified URL. The example assumes the user has the appropriate access.

// ... import statement for authentication, which includes the fetch function, is omitted for brevity.

import { overwriteFile, getSourceUrl } from "@inrupt/solid-client";

// ... Various logic, including login logic, omitted for brevity.

const MY_POD_URL = "https://example.com/mypod/";

// Upload selected files to Pod
function handleFiles() {
  const fileList = document.getElementById('fileinput').files;

  fileList.forEach(file => {
    writeFileToPod(file, `${MY_POD_URL}uploadedFiles/${file.name}`, fetch);
  });
}

// Upload File to the targetFileURL.
// If the targetFileURL exists, overwrite the file.
// If the targetFileURL does not exist, create the file at the location.
async function writeFileToPod(file, targetFileURL, fetch ) {
  try {
    const savedFile = await overwriteFile(  
      targetFileURL,                              // URL for the file.
      file,                                       // File
      { contentType: file.type, fetch: fetch }    // mimetype if known, fetch from the authenticated session
    );
    console.log(`File saved at ${getSourceUrl(savedFile)}`);

  } catch (error) {
    console.error(error);
  }
}

In the example, if the uploadedFiles Container does not exist when saving the file, the Solid server creates it to save the file to the specified URL.

Save a File into an Existing Container

To specify only the URL of the parent Container during the save, i.e., to let the Solid server determine the name of your file in the Container, use saveFileInContainer(). To use saveFileInContainer(), pass it the following parameters:

Container URL

The URL of the Container where you wish to place the file. The Container must already exist.

Options object

An object that includes the following options: { slug: <name>, contentType: <MIME type>, fetch: <fetch func> } slug Optional. The suggested file name. There is no guarantee that the Solid server will use the slug as the saved file name. If the Solid server decides to use the slug as the file name but the slug matches an already existing file in the specified Container, the Solid server creates a new name for your file. That is, the function does not overwrite existing files. fetch fetch function from an authenticated session if accessing restricted Resource (i.e., the general public cannot add files to the specified Container). See Authentication. Optional if the general public can add files to the specified Container. contentType Optional. MIME type.

Note

• To use saveFileInContainer(), the user must have Append and/or Write access to the Container. For more information on user access, see Access Policies: Universal API. See also Authentication.

• With saveFileInContainer(), you do not control the name, and thus the URL, of your file. The Solid server may or may not use the suggested slug as the file name.

• If the specified Container does not exist, the save operation fails.

The following example reads local files and uses saveFileInContainer() to save the files into the specified Container. The example assumes the user has the appropriate access.

BrowserNode.JS

// ... import statement for authentication, which includes the fetch function, is omitted for brevity.

import { saveFileInContainer, getSourceUrl } from "@inrupt/solid-client";

// ... Various logic, including login logic, omitted for brevity.

const MY_POD_URL = "https://example.com/mypod/";

// Upload selected files into Container
function handleFiles() {
  const fileList = document.getElementById('fileinput').files;

  fileList.forEach(file => {
    placeFileInContainer(file, `${MY_POD_URL}uploadedFiles/`);
  });
}

// Upload file into the targetContainer.
async function placeFileInContainer(file, targetContainerURL) {
  try {
    const savedFile = await saveFileInContainer(
      targetContainerURL,           // Container URL
      file,                         // File 
      { slug: file.name, contentType: file.type, fetch: fetch }
    );
    console.log(`File saved at ${getSourceUrl(savedFile)}`);
  } catch (error) {
    console.error(error);
  }
}

After saving the file, the example uses getSourceUrl on the returned file to determine the saved filename.

Delete a File

To delete a file, you can use deleteFile() to remove the file at the specified URL. To use deleteFile(), pass it the following parameters:

File URL	The URL of the file to delete.
Options object	An object that includes the following option: { fetch: <fetch func> } fetch fetch function from an authenticated session if deleting a restricted Resource (i.e., the general public cannot delete the specified File). See Authentication. Optional if the general public can delete the Resource.

Note

The user must have Write access to the File. For more information on user access, see Access Policies: Universal API. See also Authentication.

The following example uses deleteFile() to delete the specified file. The example assumes the user has the appropriate access.

BrowserNode.JS

// ... import statement for authentication, which includes the fetch function, is omitted for brevity.

import { deleteFile } from "@inrupt/solid-client";

// ... Various logic, including login logic, omitted for brevity.

try {
  // Delete the specified file from the Pod.
  await deleteFile(
    "https://example.com/some/boring/file",  // File to delete
    { fetch: fetch }                         // fetch function from authenticated session
  );
  console.log("Deleted::  https://example.com/some/boring/file");
} catch (err) {
  console.error(err);
}

[1] (1,2,3,4)

File represents a Blob.