NodeJS spawn stdout string format

Question

I'm spawning a process in node and tracking the output of the command like this:

proc.stdout.on("data", function (data) {
    console.log(data.toString());
});

It works well, however, the output seems to be splitting the lines:

npm http
 304 https://registry.npmjs.org/underscore

The above is just one line out of the response from an npm install. Typically this is all in one line, it's also adding line breaks before and after the response. Is there a way to get the data output to look like the standard run, i.e. line-by-line?

robertklep · Accepted Answer · 2013-11-28 18:31:40Z

28

Streams are buffered and emit data events whenever they please (so to speak), not on strict boundaries like lines of text.

But you can use the readline module to parse the buffers into lines for you:

var child_process = require('child_process');
var readline      = require('readline');
var proc          = child_process.spawn(...);

readline.createInterface({
  input     : proc.stdout,
  terminal  : false
}).on('line', function(line) {
  console.log(line);
});

answered Nov 28, 2013 at 18:31

robertklep

205k38 gold badges420 silver badges412 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

tim-montague · Accepted Answer · 2017-01-07 09:43:25Z

10

There are 3 solutions which come to mind:

// solution #1
process.stdout.write(data);

// solution #2
console.log(data.toString().replace(/[\n\r]/g, ""));

// solution #3
var child_process = require('child_process');
var readline = require('readline');
var proc = child_process.spawn(...);
readline.createInterface({
  input: proc.stdout,
  terminal: false
}).on('line', function(line) {
  console.log(line);
});

edited Jan 7, 2017 at 9:43

answered Jun 1, 2014 at 1:02

tim-montague

17.6k6 gold badges68 silver badges61 bronze badges

Collectives™ on Stack Overflow

NodeJS spawn stdout string format

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related