Mac OSX and Linux support.

The system's IP address is obtained

#!/usr/bin/env node

var os = require('os');

var osType = os.type();

var search = function() {};

if (osType === 'Darwin') {
 var nic = 'en0'; // Mac OSX

 search = function(result) {
  for (var i = 0; i < res.length; i++) {
   var d = res[i].split('\n');
   for (var j = 0; j < d.length; j++) {
    var l = d[j].replace(/(\t)+/g, '');
    var ans = l.match(/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/); // 先頭のみ
    if (ans) {
     console.log(ans[0]);
   }
   }
  }
 };
} else if (osType === 'Linux') {
 var nic = 'eth0'; // Linux

 search = function(result) {
  for (var i = 0; i < res.length; i++) {
   var d = res[i].split('\n');
   for (var j = 0; j < d.length; j++) {
    var l = d[j].replace(/(\t)+/g, '');
    var ans = l.match(/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/); // 先頭のみ
    if (ans) {
     console.log(ans[0]);
   }
   }
  }
 };
} else {
 console.log('not support os.');
 process.exit(1);
}

var spawn = require('child_process').spawn;
var ifconfig = spawn('/sbin/ifconfig', [nic]);

var res = new Array();

ifconfig.stdout.setEncoding('utf8');
ifconfig.stdout.addListener('data', function(result) {
 //res.push(result.replace(/(\n|\t)+/g, ''));
 res.push(result);
});

ifconfig.stderr.setEncoding('utf8');
ifconfig.stderr.addListener('data', function(result) {
 //res.push(result.replace(/(\n|\t)+/g, ''));
 res.push(result);
});

ifconfig.addListener('exit', function(result) {
 search(result);
});