streamFileDownload.js

// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * This application demonstrates how to perform basic operations on files with
 * the Google Cloud Storage API.
 *
 * For more information, see the README.md under /storage and the documentation
 * at https://cloud.google.com/storage/docs.
 */
const path = require('path');
const cwd = path.join(__dirname, '..');
const fs = require('fs');

function main(
  bucketName = 'my-bucket',
  fileName = 'test.txt',
  destFileName = path.join(cwd, 'downloaded.txt')
) {
  // [START storage_stream_file_download]
  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // The ID of your GCS bucket
  // const bucketName = 'your-unique-bucket-name';

  // The ID of your GCS file
  // const fileName = 'your-file-name';

  // The filename and file path where you want to download the file
  // const destFileName = '/local/path/to/file.txt';

  // Imports the Google Cloud client library
  const {Storage} = require('@google-cloud/storage');

  // Creates a client
  const storage = new Storage();

  async function streamFileDownload() {
    // The example below demonstrates how we can reference a remote file, then
    // pipe its contents to a local file.
    // Once the stream is created, the data can be piped anywhere (process, sdout, etc)
    await storage
      .bucket(bucketName)
      .file(fileName)
      .createReadStream() //stream is created
      .pipe(fs.createWriteStream(destFileName))
      .on('finish', () => {
        // The file download is complete
      });

    console.log(
      `gs://${bucketName}/${fileName} downloaded to ${destFileName}.`
    );
  }

  streamFileDownload().catch(console.error);
  // [END storage_stream_file_download]
}
main(...process.argv.slice(2));