var casper = require('casper').create();

casper.on('resource.received', function(resource) {
    var dlurl = casper.echo(resource.url);
    this.download(dlurl, '/home/asad/google237/' + dlurl);
});

casper.start('http://google.com/', function() {
    // emitting a custom event
    this.emit('google.loaded');
});

casper.run();