Spiders & Bots
Web scraping ( web harvesting or web data extraction ) is a computer software technique of extracting information from websites . Usually, such software programs simulate human exploration of the World Wide Web by either implementing low-level Hypertext Transfer Protocol (HTTP), or embedding a fully-fledged web browser, such as Internet Explorer or Mozilla Firefox . Web scraping is closely related to web indexing , which indexes information on the web using a bot or web crawler and is a universal technique adopted by most search engines.
YaCy (read "ya see") is a free distributed search engine , built on principles of peer-to-peer (P2P) networks. [ 2 ] [ 3 ] Its core is a computer program written in Java distributed on several hundred computers, as of September 2006 [update] , so-called YaCy-peers. Each YaCy-peer independently crawls through the Internet, analyzes and indexes found web pages, and stores indexing results in a common database (so called index) which is shared with other YaCy-peers using principles of P2P networks. Compared to semi-distributed search engines, the YaCy-network has a decentralised architecture.
Nonprofit Common Crawl Offers a Database of the Entire Web, For Free, and Could Open Up Google to New CompetitionGoogle famously started out as little more than a more efficient algorithm for ranking Web pages. But the company also built its success on crawling the Web—using software that visits every page in order to build up a vast index of online content. A nonprofit called Common Crawl is now using its own Web crawler and making a giant copy of the Web that it makes accessible to anyone. The organization offers up over five billion Web pages, available for free so that researchers and entrepreneurs can try things otherwise possible only for those with access to resources on the scale of Google’s.
More precisely, I crawled 250,113,669 pages for just under 580 dollars in 39 hours and 25 minutes, using 20 Amazon EC2 machine instances. I carried out this project because (among several other reasons) I wanted to understand what resources are required to crawl a small but non-trivial fraction of the web. In this post I describe some details of what I did. Of course, there’s nothing especially new: I wrote a vanilla (distributed) crawler, mostly to teach myself something about crawling and distributed computing.
Distributed web crawling is a distributed computing technique whereby Internet search engines employ many computers to index the Internet via web crawling . Such systems may allow for users to voluntarily offer their own computing and bandwidth resources towards crawling web pages. By spreading the load of these tasks across many computers, costs that would otherwise be spent on maintaining large computing clusters are avoided. [ 1 ]
Be careful - this is a robot and hence can be used to traverse many links - it should be used with care and is not designed to be let loose on the Internet at large. Its primary design goal was to be able to test HTTP/1.1 pipelining features . The robot has a large set of command line options that can be used in a large set of different combinations. You can try and see this simple script in order to see an example of how it can be run. <p style="text-align:right;color:#A8A8A8"></p>
Webbots, Spiders, and Screen Scrapers is "unmatched to my knowledge in how it covers PHP/CURL. It explains to great details on how to write web clients using PHP/CURL, what pitfalls there are, how to make your code behave well and much more." — Daniel Stenberg, creator of cURL ( Read More ) View a sample chapter, Chapter 2: Ideas for Webbots View a sample chapter, Chapter 3: Downloading Web Pages
Internet bots , also known as web robots , WWW robots or simply bots , are software applications that run automated tasks over the Internet . Typically, bots perform tasks that are both simple and structurally repetitive, at a much higher rate than would be possible for a human alone. The largest use of bots is in web spidering , in which an automated script fetches, analyzes and files information from web servers.
Introduction A web crawler is a program that browses the World Wide Web in a methodical and automated manner. It also known as web spider, web robot, ant, bot, worm, and automated indexer.
Disclosure: the writer of this article, Emre Sokullu, joined Hakia as a Search Evangelist in March 2007. The following article in no way represents Hakia's views - it is Emre's personal opinions only. Google is like a young mammoth, already very strong but still growing.
A Web crawler is an Internet bot that systematically browses the World Wide Web , typically for the purpose of Web indexing .