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# system.js

¶

    /*
     * system.js: Simple memory-based store for process environment variables and
     *            command-line arguments.
     *
     * (C) 2011, Charlie Robbins
     *
     */

    var util = require('util'),
        Memory = require('./memory').Memory;

¶

### function System (options)

#### @options {Object} Options for this instance.

Constructor function for the System nconf store, a simple abstraction around the Memory store that can read process environment variables and command-line arguments.

    var System = exports.System = function (options) {
      options = options || {};
      Memory.call(this, options);

      this.type      = 'system';
      this.overrides = options.overrides || null;
      this.env       = options.env       || false;
      this.argv      = options.argv      || false;
    };

¶

Inherit from the Memory store

    util.inherits(System, Memory);

¶

### function loadSync ()

Loads the data passed in from `process.env` into this instance.

    System.prototype.loadSync = function () {
      if (this.env) {
        this.loadEnv();
      }

      if (this.argv) {
        this.loadArgv();
      }

      if (this.overrides) {
        this.loadOverrides();
      }

      return this.store;
    };

¶

### function loadOverrides ()

Loads any overrides set on this instance into the underlying managed `Memory` store.

    System.prototype.loadOverrides = function () {
      if (!this.overrides) {
        return;
      }

      var self = this,
          keys = Object.keys(this.overrides);

      keys.forEach(function (key) {
        self.set(key, self.overrides[key]);
      });

      return this.store;
    };

¶

### function loadArgv ()

Loads the data passed in from the command-line arguments into this instance.

    System.prototype.loadArgv = function () {
      var self = this,
          argv;

      if (typeof this.argv === 'object') {
        argv = require('optimist').options(this.argv).argv;
      }
      else if (this.argv) {
        argv = require('optimist').argv;
      }

      if (!argv) {
        return;
      }

      Object.keys(argv).forEach(function (key) {
        self.set(key, argv[key]);
      });

      return this.store;
    };

¶

### function loadEnv ()

Loads the data passed in from `process.env` into this instance.

    System.prototype.loadEnv = function () {
      var self = this;

      if (!this.env) {
        return;
      }

      Object.keys(process.env).filter(function (key) {
        return !self.env.length || self.env.indexOf(key) !== -1;
      }).forEach(function (key) {
        self.set(key, process.env[key]);
      });

      return this.store;
    };