screencap.js

var page = require('webpage').create();
var system = require('system');

var cur_date = new Date();
var folder = cur_date.getFullYear() + '-' + (cur_date.getMonth()+1) + '-' + cur_date.getDate();// +'_'+ cur_date.getHours() +cur_date.getMinutes();

var url = system.args[1];
var filename = url.replace(/[^a-z0-9]/gi, '_').toLowerCase();
page.open(url, function () {
        page.render(folder+'/'+filename+'.png');
        system.stdout.writeLine('done : '+ url);
        phantom.exit(0);
});