呼び出されるモジュール側から呼び出し（実行スクリプト）側のパスを取得する

app.js

#!/usr/bin/env node
var path = require('path');
var waf  = require('w-a-f');

waf().use(require(path.join(__dirname, 'middleware/wan'))())
     .use(require(path.join(__dirname, 'middleware/nyan'))())
     .use(require(path.join(__dirname, 'middleware/guu'))())
     .resume();

// wan
// nyan
// guu

waf().use('guu').use('nyan').use('wan').resume();

// guu
// nyan
// wan

guu.js

module.exports = function () {
  return funciton (next) {
    console.log('guu');
    next();
  };
};

index.js

var path = require('path');

function WAF () {
    this.middlewares = [];
}

WAF.prototype.use = function (middleware, arg) {
    'string' === typeof middleware &&
        (middleware = this.useHelp(middleware, arg));

    'function' === typeof middleware &&
        this.middlewares.push(middleware);

    return this;
};

WAF.prototype.useHelp = function (middleware_name, arg) {
    return require(path.join( path.dirname(process.argv[1])
                            , 'middleware', middleware_name ))(arg);
};

WAF.prototype.resume = function () {
    var that = this, i = 0, next = function () {
        var m = that.middlewares[i++];
        'function' === typeof m && m(next);
    };
    next();
};

module.exports = function () {
    return new WAF;
};

nyan.js

module.exports = function () {
  return funciton (next) {
    console.log('nyan');
    next();
  };
};

tree

.
|-- app.js
|-- middleware
|   |-- guu.js
|   |-- nyan.js
|   `-- wan.js
`-- node_modules
    `-- w-a-f
        |-- index.js
        `-- package.json

wan.js

module.exports = function () {
  return funciton (next) {
    console.log('wan');
    next();
  };
};