Node.js | Stream.pipeline() Method

The stream.pipeline() method is a module method that is used to the pipe by linking the streams passing on errors and accurately cleaning up and providing a callback function when the pipeline is done.

Syntax:

stream.pipeline(...streams, callback)

Parameters: This method accepts two parameters as mentioned above and described below.

  • …streams: These are two or more streams which are to be piped together.
  • callback: This function is called when the pipeline is fully done and it shows an ‘error’ if the pipeline is not accomplished.

Return Value: It returns a cleanup function.

Below examples illustrate the use of stream.pipeline() method in Node.js:



Example 1:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Node.js program to demonstrate the     
// stream.pipeline() method
  
// Including fs and zlib module
var fs = require('fs');
const zlib = require('zlib');
  
// Constructing finished from stream
const { pipeline } = require('stream');
  
// Constructing promisify from
// util
const { promisify } = require('util');
  
// Defining pipelineAsync method
const pipelineAsync = promisify(pipeline);
  
// Constructing readable stream
const readable = fs.createReadStream("input.text");
  
// Constructing writable stream
var writable = fs.createWriteStream("output.text");
  
// Creating transform stream
const transform = zlib.createGzip();
  
// Async function
(async function run() {
  try
  
    // pipelining three streams
    await pipelineAsync(
      readable,
      transform,
      writable
    );
    console.log("pipeline accomplished.");
    }
  
  // Shows error
  catch(err) {
    console.error('pipeline failed with error:', err);
  }
  })();

chevron_right


Output:

Promise {  }
pipeline accomplished.

Example 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Node.js program to demonstrate the     
// stream.pipeline() method
  
// Including fs and zlib module
var fs = require('fs');
const zlib = require('zlib');
  
// Constructing finished from stream
const { pipeline } = require('stream');
  
// Constructing promisify from
// util
const { promisify } = require('util');
  
// Defining pipelineAsync method
const pipelineAsync = promisify(pipeline);
  
// Constructing readable stream
const readable = fs.createReadStream("input.text");
  
// Constructing writable stream
var writable = fs.createWriteStream("output.text");
  
// Creating transform stream
const transform = zlib.createGzip();
  
// Async function
(async function run() {
  try
  
    // pipelining three streams
    await pipelineAsync(
      readable,
      writable,
      transform
    );
    console.log("pipeline accomplished.");
    }
  
  // Shows error
  catch(err) {
    console.error('pipeline failed with error:', err);
  }
  })();

chevron_right


Output: Here, the order of streams is not proper while piping so an error occurs.

Promise {  }
pipeline failed with error: Error [ERR_STREAM_CANNOT_PIPE]: Cannot pipe, not readable
    at WriteStream.Writable.pipe (_stream_writable.js:243:24)
    at pipe (internal/streams/pipeline.js:57:15)
    at Array.reduce ()
    at pipeline (internal/streams/pipeline.js:88:18)
    at Promise (internal/util.js:274:30)
    at new Promise ()
    at pipeline (internal/util.js:273:12)
    at run (/home/runner/ThirstyTimelyKey/index.js:33:11)
    at /home/runner/ThirstyTimelyKey/index.js:45:5
    at Script.runInContext (vm.js:133:20)

Reference: https://nodejs.org/api/stream.html#stream_stream_pipeline_streams_callback.




My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : Akanksha_Rai