Node: createWriteStream; close doesn't finish writing all data to file

[d3x0r]

Windows 7/10,
node 5.6.0, and latest builds...
This seems like something fairly critical...

"use strict";

const fs = require( 'fs' );
var outData = fs.createWriteStream( "output.txt" );
outData.write( "line one" );
outData.write( "line two" );
outData.close();

results in a file that only has 'line one' in it.
it can be several lines... I'm often missing 5 lines in this one file... but basically every file never writes all information to the file.

this might be similar to https://github.com/nodejs/node/pull/2314

[evanlucas]

Here is a working example. In order to have a guarantee that write() has finished, you must wait for the callback on it.

'use strict'

const fs = require('fs')
const stream = fs.createWriteStream('out.txt')
stream.write('line one', () => {
  stream.write('line two', () => {
    stream.close()
  }) 
})

[d3x0r]

Okay I started to dig into the code, and added some console.log( stream ); after the writes.... there's a 'pendingcb' which goes up, and things start to get buffered... so I supposed maybe if there wasn't a callback it would fail.

It will take some time to restructure the code to fit HAVING to use the callbacks.
I would still think that close operation should pend itself after the writes, or mark the stream as closed so the last write can complete the close....

but even in a more complex case where I continue on to do other work with other files for a long amount of time the output still doesn't go... so the pending writes apparently never get called without having a callback of some sort...

[Slayer95]

@d3x0r , maybe you are looking for WritableStream#end() ? That will automatically handle closing the stream for you after pending writes are done.

Note that close() is not part of the public API (https://nodejs.org/api/stream.html#stream_class_stream_writable)

[d3x0r]

I had added

outData.write( "line two" );
outData.end();
outData.close();

but that made no difference.

[vkurchatkin]

This works as expected. close immediately closes fd without flushing ending writes. Just call end and fd will be closed automatically after writes are flushed.

[d3x0r]

confirmed; replacing close with end lets it work :)

[ORESoftware]

close() is no longer a method on the writable instance, use end() instead