`util.pump` is deprecated in favor of Stream.pipe. >From the docs, http://nodejs.org/docs/latest/api/all.html#all_util_pump_readablestream_writablestream_callback : util.pump(readableStream, writableStream, [callback])#<http://nodejs.org/docs/latest/api/all.html#all_util_pump_readablestream_writablestream_callback>
Stability: 0 - Deprecated: Use readableStream.pipe(writableStream) Additionally, so long as you do the pipe in the same tick as the stream creation, you'll get the single 'error' event and thus the single call to callback. As a general rule of thumb, when piping, don't bother with the origin stream's events unless you have an explicit reason to do so. In this case it doesn't seem you do, in which case you would only handle the 'error' event once on the destination stream. Cheers, Adam Crabtree On Mon, Oct 8, 2012 at 9:44 AM, Adam Crabtree <[email protected]> wrote: > Stream.pipe, > > > http://nodejs.org/docs/latest/api/all.html#all_stream_pipe_destination_options > > will handle this for you in exactly the way you want: > > > var copy = function(from, to, cb){ > var stream = fs.createReadStream(from) > .pipe(fs.createWriteStream(to)) > > stream.on('error', cb) > stream.on('end', cb) > } > > Take a look at the source for Stream.pipe and you'll see what I'm talking > about; It wraps the 'error' event callback and emits only once, then does > its own cleanup (you'll have to call destroy yourself, although I think > maybe pipe should do this in its cleanup...). > > From https://github.com/joyent/node/blob/master/lib/stream.js: > > > source.on('error', onerror); > > dest.on('error', onerror); > > > // remove all the event listeners that were added. > > function cleanup() { > > source.removeListener('data', ondata); > > dest.removeListener('drain', ondrain); > > > source.removeListener('end', onend); > > source.removeListener('close', onclose); > > > source.removeListener('error', onerror); > > dest.removeListener('error', onerror); > > > source.removeListener('end', cleanup); > > source.removeListener('close', cleanup); > > > dest.removeListener('end', cleanup); > > dest.removeListener('close', cleanup); > > } > > > > Cheers, > Adam Crabtree > > On Sun, Oct 7, 2012 at 7:57 PM, Alexey Petrushin < > [email protected]> wrote: > >> > I'm missing how this would help ... >> With callbacks it may be something like code below: >> >> > so you'll still need to attach the two error handlers, and you'll still >> need >> > to handle the possibility of multiple notifications. >> Not sure about it but maybe `stream.destroy()` on first event should >> handle such cases. >> >> var copy = function(from, to, cb){ >> var fromStream = null >> var toStream = null >> >> var finish = function(err){ >> fromStream.destroy() >> toStream.destroy() >> cb(err) >> } >> >> fromStream = fs.createReadStream(from, function(err){ >> if(err) return cb(err) >> toStream = fs.createWriteStream(to, function(err){ >> if(err) return cb(err) >> >> fromStream.on('error', finish) >> toStream.on('error', finish) >> fromStream.on('end', finish) >> fromStream.pipe(toStream) >> }) >> }) >> } >> >> On Monday, October 8, 2012 6:41:43 AM UTC+4, Martin Cooper wrote: >> >>> On Sun, Oct 7, 2012 at 5:54 PM, Alexey Petrushin >>> <[email protected]> wrote: >>> > Tried to copy files using streams and pipe and got funny results. >>> Let's >>> > consider following code (highlighted version https://gist.github.com/* >>> *3850106 <https://gist.github.com/3850106> >>> > ): >>> > >>> > var copy = function(from, to, cb){ >>> > var fromStream = fs.createReadStream(from) >>> > fromStream.on('error', cb) >>> > var toStream = fs.createWriteStream(to) >>> > toStream.on('error', cb) >>> > fromStream.on('end', cb) >>> > } >>> > >>> > copy('non existing file a', 'non existing dir/file b', >>> function(err){ >>> > console.log(err) >>> > }) >>> > >>> > There are errors in both streams (non existing source file and no >>> parent >>> > directory for destination file) - so, both of them will emit >>> > 'error' event, and the callback will be called twice with both errors. >>> > >>> > // Error will be reported twice: >>> > // >>> > // { [Error: ENOENT, open 'non existing file a'] errno: 34, >>> > // code: 'ENOENT', path: 'non existing file a' } >>> > // { [Error: ENOENT, open 'non existing dir/file b'] errno: 34, >>> > // code: 'ENOENT', path: 'non existing dir/file b' } >>> > >>> > I found the solution by looking at the source of `util.pump` - it does >>> it by >>> > wrapping callback into function that calls callback only once - for >>> the fist >>> > error and ignoring others. >>> > >>> > But maybe it would be nice to have a callback for `createXxxStream` or >>> > something like 'ready' or 'success' events to know that it created >>> > successfully? >>> >>> I'm missing how this would help. If there was such an event, either >>> stream could still emit an error before it (e.g. open error) or after >>> it (e.g. read or write error), so you'll still need to attach the two >>> error handlers, and you'll still need to handle the possibility of >>> multiple notifications. What would be the benefit of having another >>> event to listen for? >>> >>> -- >>> Martin Cooper >>> >>> >>> > -- >>> > Job Board: http://jobs.nodejs.org/ >>> > Posting guidelines: >>> > https://github.com/joyent/**node/wiki/Mailing-List-** >>> Posting-Guidelines<https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines> >>> > You received this message because you are subscribed to the Google >>> > Groups "nodejs" group. >>> > To post to this group, send email to [email protected] >>> > To unsubscribe from this group, send email to >>> > nodejs+un...@**googlegroups.com >>> > For more options, visit this group at >>> > http://groups.google.com/**group/nodejs?hl=en?hl=en<http://groups.google.com/group/nodejs?hl=en?hl=en> >>> >> -- >> Job Board: http://jobs.nodejs.org/ >> Posting guidelines: >> https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines >> You received this message because you are subscribed to the Google >> Groups "nodejs" group. >> To post to this group, send email to [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/nodejs?hl=en?hl=en >> > > > > -- > Better a little with righteousness > than much gain with injustice. > Proverbs 16:8 > -- Better a little with righteousness than much gain with injustice. Proverbs 16:8 -- Job Board: http://jobs.nodejs.org/ Posting guidelines: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines You received this message because you are subscribed to the Google Groups "nodejs" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nodejs?hl=en?hl=en
