Stefan Demo

gistfile1.js

var sys = require('sys')
var exec = require('child_process').exec;
var child;
var vpnClientAddrs;

// We can use function pull ups which helps keep things clean. 
// The pull up means we can use the function here even though it is below

getIpAddresses( doSomethingWithResults );


// finds external IP adresses of all clients by matching
// IP addresses after "P-t-P:" in ifconfig
// can't seem to do this with os.networkInterfaces() - it only
// seems to have the IP of this machine 

function getIpAddresses( callback ) {
    return exec("ifconfig | grep -P -o \"(?<=P-t-P:)(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\" ", function (error, stdout, stderr) {
        vpnClientAddrs = stdout.split("\n");
        
        // By convention, normally an error is the first argument of all callback
        callback( error, vpnClientAddrs );
    });
}

// An example

function doSomethingWithResults( err, results ) {
    if ( err ) {
        console.error( 'shit, that failed', err );
        return;
    }
    console.log( 'That worked' );
    console.log( results );
}