Simple lock-file mechanism for nodeJS

simple-lockfile-for-nodejs.js

var fs = require('fs');
var path = require('path');

if (typeof exports === 'undefined') var exports = {};

exports.exists = function(filename) {
	try {
		return (fs.lstatSync(filename) ? true : false);
	}
	catch (err) {
		return false;
	}
};

exports.create = function(filename,  contents) {
	try {
		if (!contents) contents = '';
		fs.writeFileSync(filename, contents);
		return true;
	}
	catch (err) {
		return false;
	}
};

exports.remove = function(filename) {	
	try {
		return fs.unlinkSync(filename);
	}
	catch (err) {
		return false;
	}
};

@adminy This was done 9 years ago so a lot has happened since then. I'd have to be honest and admit this stuff is all outdated here :)

@martintajur Code lives on ... provide a nice gist to others, something like:

const { promises, constants } = require('fs')
const lockFile = path => {
    const lockPath = `${path}.lock`
    return promises.open(lockPath, constants.O_CREAT | constants.O_EXCL | constants.O_RDWR).catch(() => lockFile(path))
}
const unlockFile = path => {
    const lockPath = `${path}.lock`
    return promises.unlink(lockPath).catch(() => unlockFile(path)
}

Usage:

const main = async () => {
    const path = 'some/path/to/file'
    await lockFile(path)
    // Do something with the file
    // ...
    await unlockFile(path)
}
main()

Proper locking mechanisms are probably more intricate than that, taking in consideration oses and their filesystems but It is nice to have a simple example to find somewhere.