sessid.js

browser.addCommand('get_sessid_from_url', function (c) {
    return browser.url().then(function(res) {
        return res.value.match(/^https:\/\/(\d+)\./)[1];
    });
});

// Usage

it('navigate to cgi/wordpress_tools', function*() {
    sess_id = yield browser.get_sessid_from_url();
    console.log(sess_id);
});