How to specify USB mass storage among USB devices?

Question

I am making a function for users to transfer data to USB and I am using 'usb' package for it. If I do const devices = getDeviceList();, then I get all devices info connected through USB such as mouse, and keyboard. However, I should specify only USB mass storage. In this case, how can I specify it? Any suggestion is always welcome and thank you in advance!

FYI: I tried to specify it, but console.log("usb device is: ", usbDevice); gives me null

This is my code:

import {usb, getDeviceList} from "usb";
import fs from "fs";
import path from "path";

async function path2usb(selectedMeasures) {
  // Assuming selectedMeasures is an array of data to be exported
  try {
    usb.on("attach", function (device) {
      console.log("USB device attached:");
      console.log(device);
    });

    usb.on("detach", function (device) {
      console.log("USB device detached:");
      console.log(device);
    });

    // Get a list of USB devices
    const devices = getDeviceList();
    console.log("devices are: ", devices);
    // Find the first USB mass storage device (e.g., a USB stick)
    let usbDevice = null;
    for (const device of devices) {
      const descriptor = device.deviceDescriptor;
      if (
        descriptor &&
        descriptor.bDeviceClass === 0x08 && // USB mass storage class
        descriptor.bDeviceSubClass === 0x06 && // USB mass storage subclass
        (descriptor.bDeviceProtocol === 0x50 || descriptor.bDeviceProtocol === 0x01) // Bulk-only transport or SCSI transparent command set
      ) {
        usbDevice = device;
        break; // Stop iterating once the USB stick is found
      }
    }
    console.log("usb device is: ", usbDevice);
    if (usbDevice) {
      usbDevice.open();
      const usbInterface = usbDevice.interface(0);
      usbInterface.claim();

      const endpoint = usbInterface.endpoint(0x81); // Assuming the endpoint is 0x81, you may need to check the endpoint address for your specific USB device.

      if (endpoint) {
        const folderName = selectedMeasures.join("_"); // Combine the selected measures to form the folder name
        const targetFolderPath = path.join("/data", folderName); // Create the target folder path in the 'data' directory

        // Check if the folder exists
        if (!fs.existsSync(targetFolderPath)) {
          throw new Error("Folder not found in 'data' directory.");
        }

        const targetFilePath = path.join(
          `/dev/${endpoint.deviceDescriptor.iSerialNumber}`,
          `${folderName}.txt`
        ); // Create the target file path in the USB mass storage device

        // Write the exported data to the file
        fs.writeFileSync(targetFilePath, selectedMeasures.join("\n"));

        console.log(`Data exported to USB-drive: ${targetFilePath}`);
        return targetFilePath;
      } else {
        // If the endpoint is not found, throw an error
        throw new Error("USB endpoint not found!");
      }
    } else {
      // If no USB mass storage device is found, throw an error
      throw new Error("No USB Mass Storage device found!");
    }
  } catch (error) {
    console.error("Error exporting data to USB drive:", error.message);
    throw error;
  }
}

export { path2usb };

and this is what I get from console.log:

Answer 1

Since you seem to be using Linux I would suggest that you look at the symbolic links in /dev/disk/by-label. You can then use libudev to look at the parents of those devices and see if any of the parents is a USB device. The library libudev is a widely-used C library on Linux, and there is probably a node.js binding for it that would for you.

As a proof of concept, before you write any code, just run ls -l /dev/disk/by-label, and then run udevadm info --attribute-walk /dev/disk/by-label/NAME (where NAME is some name you saw in the directory listing). Look for usb in the output of that command.