How to chain write stream, immediately with a read stream in Node.js 0.10?

Question

The following line will download an image file from a specified url variable:

var filename = path.join(__dirname, url.replace(/^.*[\\\\\\/]/, \'         


        

Answer 1

// create 'fs' module variable
var fs = require("fs");

// open the streams
var readerStream = fs.createReadStream('inputfile.txt');
var writerStream = fs.createWriteStream('outputfile.txt');

// pipe the read and write operations
// read input file and write data to output file
readerStream.pipe(writerStream);

Answer 2

I think the confusion in chaining the pipes is caused by the fact that the pipe method implicitly "makes choices" on it's own on what to return. That is:

readableStream.pipe(writableStream) // Returns writable stream
readableStream.pipe(duplexStream) // Returns readable stream

But the general rule says that "You can only pipe a Writable Stream to a Readable Stream." In other words only Readable Streams have the pipe() method.

Answer 3

request(url).pipe(fs.createWriteStream(filename)).pipe(writestream);

is the same as this:

var fileStream = fs.createWriteStream(filename);
request(url).pipe(fileStream);
fileStream.pipe(writestream);

So the issue is that you are attempting to .pipe one WriteStream into another WriteStream.