Writing data to text file in Node.js

Question

Currently, I have the following block of code:

net = require('net');
var clients = [];

net.createServer(function(s) {

  clients.push(s);

  s.on('data', function (data) {
    clients.forEach(function(c) {
      c.write(data);
    });
    process.stdout.write(data);//write data to command window
  });

  s.on('end', function() {
    process.stdout.write("lost connection");
  });

}).listen(9876);

Which is used to set up my Windows computer as a server and receive data from my linux computer. It is currently writing data to the command window. I would like to write the data into a text file to specific location, how do i do this?

Note that Java is not the same as JavaScript; Node.js is server-side *JavaScript*. — dimo414, Apr 01 '14 at 20:07
Fortunately the language you are working in is JavaScript, you don't need to know anything about Java. — dimo414, Apr 01 '14 at 20:10

SomeKittens · Accepted Answer · 2014-04-01T20:45:27.487

6

Use the fs module to deal with the filesystem:

var net = require('net');
var fs = require('fs');
// ...snip
s.on('data', function (data) {
  clients.forEach(function(c) {
    c.write(data);
  });

  fs.writeFile('myFile.txt', data, function(err) {
    // Deal with possible error here.
  });
});

edited Apr 01 '14 at 20:45

answered Apr 01 '14 at 20:14

SomeKittens

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2

By default, writeFile() will overwrite anything that was already in the file, so this answer will only leave the last 'data' item in the file. – cybersam Apr 01 '14 at 20:22
well, this exactly wt i want to do, over write the data, and leave the latest data in the text file only. – FWing Apr 01 '14 at 20:43
However, the problem I am having at the moment is, I dont have any error, but i cant file the .txt file even with the search function of windows :/ – FWing Apr 01 '14 at 20:44
@FWing The txt file should be in the directory where you ran `node` – SomeKittens Apr 01 '14 at 20:47
oh alrite, thank you, i got it, not sure why the search function doesnt work – FWing Apr 01 '14 at 21:09

score 4 · Answer 2 · answered Apr 01 '14 at 20:19

4

You should read up on the File System support in node.js.

The following method is probably the simplest way to do what you want, but it is not necessarily the most efficient, since it creates/opens, updates, and then closes the file every time.

function myWrite(data) {
    fs.appendFile('output.txt', data, function (err) {
      if (err) { /* Do whatever is appropriate if append fails*/ }
    });
}

answered Apr 01 '14 at 20:19

cybersam

63,203
6
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is it a must that i hv to be prepare when i encounter an error? i have no idea wt to do? – FWing Apr 01 '14 at 20:29
You could just output an error to the console, if you don't know what else to do. For example: console.error("Failed to output data. Data: %s, Error: %s", data, err); – cybersam Apr 01 '14 at 20:50
same problem here, i dont hv any error, but i couldnt find my file, im not sure if the code is working – FWing Apr 01 '14 at 20:51
You can explicitly specify the full path for the file, so that you know where it goes. – cybersam Apr 01 '14 at 21:02
yes, i made it, thank you very much! – FWing Apr 01 '14 at 21:17
The default directory is the directory that holds your node.js code. – cybersam Apr 01 '14 at 21:20

Writing data to text file in Node.js

2 Answers2