How to use cms systems like drupal and so on for crawl only?

Question

I want to display the data by my own,

use cms to crawl the data only.

Anyone can share the experience and give me some clue where the entry point is?

Answer 1

I will re-interpret the question: "How do I use Drupal to create and aggregate content, but display it through a means other than HTML web pages?"

The answer is to focus on generating XML feeds. In Drupal Core, the default rss feed is at /rss.xml. Every taxonomy listing page also has an RSS feed associated with it. To expand further on those options, make use of the RSS feed display in Views, the Views Datasource module to add even greater varieties of data (JSON output, for example), and even the RDF projects if you want to be on the cutting edge.

If you do not want to display any of this content as HTML use hook_menu_alter() on almost every page generated in Drupal- run down every node and block it. At that point, this question becomes kind of academic, because if you are not interested in having a theme Layer, any CMS is the wrong tool for the job.