CODEWITHSUNDEEP
javascriptnode.jsfs
Subhendu
Subhendu

Reputation: 81

Nodejs - fs.appendFileSync throws Error EBUSY

I am trying to append lines to a file in nodejs. I have written the following peice of code .

/* Name :  test.js */
/* globals require,__dirname */
var fs = require("fs");
for (var i = 0; i < 100000; i++) {
    fs.appendFileSync(__dirname+'/out.txt', "line " + i + "\n");
}

But when I run this program, I am getting the following error. 

$ node test.js
fs.js:584
  return binding.open(pathModule._makeLong(path), stringToFlags(flags), mode);
                                                  ^

Error: EBUSY: resource busy or locked, open 'd:\<redacted>\out.txt'
    at Error (native)
    at Object.fs.openSync (fs.js:584:18)
    at Object.fs.writeFileSync (fs.js:1224:33)
    at Object.fs.appendFileSync (fs.js:1283:6)
    at Object.<anonymous> (d:\<redacted>\test.js:3:8)
    at Module._compile (module.js:425:26)
    at Object.Module._extensions..js (module.js:432:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:313:12)
    at Function.Module.runMain (module.js:457:10)

I have searched but could not find any reason or solution for this. Can someone please explain why this Error occurs and how to fix it ?

When I try the following method it works but this is not very feasible for the problem I am attempting to solve. 

/* globals require,__dirname */
var fs = require("fs");
var buffer = "";

for (var i = 0; i < 100000; i += 1) {
    var line =  'line ' + i + '\n';
    buffer += line;                 // keep the line in buffer    
}

fs.appendFileSync(__dirname+'/out.txt', buffer);   // now write the buffer

Thanks in advance.

Upvotes: 1

Views: 4135

Answers (1)

Shanoor
Shanoor

Reputation: 13692

Your code works for me but it's awfully slow, it takes minutes to finish writing in the file (269621.425ms to be exact). Your issue is likely because of so many access in a very short time, I guess it works for me because I'm using an SSD.

For your issue, streams might be very helpful. It's fast and memory efficient (you don't have to store a giant buffer variable). I don't know what you want to do exactly so here is your example written using streams (I used event-stream for convenience):

var fs = require('fs');
var es = require('event-stream');

console.time('done in');
es.readable(function (count, next) {
    for (var i = 0; i < 100000; i++) {
        this.emit('data', 'line ' + i + "\n");
    }
    this.emit('end');
    console.timeEnd('done in');
    next();
}).pipe(fs.createWriteStream('out.txt'));

done in: 90.561ms

Upvotes: 2

Related Questions