CODEWITHSUNDEEP
node.js
user644745
user644745

Reputation: 5723

callback to handle completion of pipe

I am using the following node.js code to download documents from some url and save it in the disk. I want to be informed about when the document is downloaded. i have not seen any callback with pipe.Or, Is there any 'end' event that can be captured on completion of download ?

request(some_url_doc).pipe(fs.createWriteStream('xyz.doc'));

Upvotes: 215

Views: 146978

Answers (5)

Abu Shumon
Abu Shumon

Reputation: 1994

I found an a bit different solution of my problem regarding this context. Thought worth sharing.

Most of the example create readStreams from file. But in my case readStream has to be created from JSON string coming from a message pool. 

var jsonStream = through2.obj(function(chunk, encoding, callback) {
                    this.push(JSON.stringify(chunk, null, 4) + '\n');
                    callback();
                });
// message.value --> value/text to write in write.txt 
jsonStream.write(JSON.parse(message.value));
var writeStream = sftp.createWriteStream("/path/to/write/write.txt");

//"close" event didn't work for me!
writeStream.on( 'close', function () {
    console.log( "- done!" );
    sftp.end();
    }
);

//"finish" event didn't work for me either!
writeStream.on( 'close', function () {
    console.log( "- done!"
        sftp.end();
        }
);

// finally this worked for me!
jsonStream.on('data', function(data) {
    var toString = Object.prototype.toString.call(data);
    console.log('type of data:', toString);
    console.log( "- file transferred" );
});

jsonStream.pipe( writeStream );

Upvotes: 5

blak3r
blak3r

Reputation: 16546

Here's a solution that handles errors in requests and calls a callback after the file is written:

request(opts)
    .on('error', function(err){ return callback(err)})
    .pipe(fs.createWriteStream(filename))
    .on('finish', function (err) {
        return callback(err);
    });

Upvotes: 4

Pickels
Pickels

Reputation: 34660

Streams are EventEmitters so you can listen to certain events. As you said there is a finish event for request (previously end).

 var stream = request(...).pipe(...);
 stream.on('finish', function () { ... });

For more information about which events are available you can check the stream documentation page.

Upvotes: 333

ruX
ruX

Reputation: 7472

Code snippet for piping content from web via http(s) to filesystem. As @starbeamrainbowlabs noticed event finish does job

var tmpFile = "/tmp/somefilename.doc";

var ws = fs.createWriteStream(tmpFile);
ws.on('finish', function() {
  // pipe done here, do something with file
});

var client = url.slice(0, 5) === 'https' ? https : http;
client.get(url, function(response) {
  return response.pipe(ws);
});

Upvotes: 9

vr3C
vr3C

Reputation: 1774

Based nodejs document, http://nodejs.org/api/stream.html#stream_event_finish, it should handle writableStream's finish event.

var writable = getWriteable();
var readable = getReadable();
readable.pipe(writable);
writable.on('finish', function(){ ... });

Upvotes: 45

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