rwd

Warns if the process has been started with the wrong cwd

rwd means real working directory.
Global modules don't need the rwd module.

Did you know why the people prefix __dirname before a path?

var fs = require ("fs");
fs.existsSync (__dirname + "/file");

It's because the process.cwd() function returns the shell's current working directory instead of the directory where lives the main script of your application.

Look at this example:

$ pwd
/home/user1
$ mkdir dir
$ cat > dir/app.js
console.log (process.cwd ());
$ node dir/app.js
/home/user1
$ cd dir && node app.js
/home/user1/dir

If you execute the main script with a relative path like the above example ($ node dir/app.js), very bad things could happen and it's nearly impossible to detect why your code is not working as expected. This is a feature found on all the programming languages because it's a thing related with the OS, not with the programming language itself.

$ node dir/app behaves different than $ cd dir && node app.

The following example illustrates a very ingenuous script, but depending on how you execute it, very dangerous things could happen:

//$ node dir/app.js
var fs = require ("fs");
if (fs.existsSync ("settings.json")){
    doSomethingUseful ();
}else{
    //Warning!!
    saveToDatabaseDefaultSettings ();
}

This can be easily fixed changing the cwd at runtime, but it's discouraged. The best way to ensure that the application is started correctly is to require the rwd module. I recommend to put it in the very first line of your main file:

//app.js
require ("rwd");

The module is automatically uncached.

Then, if you start the process with a relative path, eg: $ node dir/app.js, a message will be printed and the process will exit with code 1, something similar to this:

The process has been started this way:

  $ node dir/app.js

Better alternatives:

  $ cd dir && node app.js
  $ node <absolute_path>/dir/app.js

This way, you don't need to prefix the paths with __dirname because if the process doesn't finish this means that the cwd is the same as the directory of the main file.

Alternatives

For your convenience you can create a global variable similar to __dirname which can be used safely from any module (__dirname is local to the file). For example, you can run this snippet in the main file:

var path = require ("path");
global.__root = path.dirname (process.mainModule.filename);

Then, every time you need to use a relative path from the root, you can prefix it with __root:

var fs = require ("fs");
if (fs.existsSync (__root + "/settings.json")){
    doSomethingUseful ();
}