I am making a simple web spider and I was wondering if there is a way that can be triggered in my PHP code that I can get all the webpages on a domain...
e.g Lets say I wanted to get all the webpages on Stackoverflow.com . That means that it would get:
https://stackoverflow.com/questions/ask
pulling webpages from an adult site -- how to get past the site agreement?
https://stackoverflow.com/questions/1234214/
Best Rails HTML Parser
And all the links. How can I get that. Or is there an API or DIRECTORY that can enable me to get that?
Also is there a way I can get all the subdomains?
Btw how do crawlers crawl websites that don't have SiteMaps or Syndication feeds?
Cheers.
If a site wants you to be able to do this, they will probably provide a Sitemap. Using a combination of a sitemap and following the links on pages, you should be able to traverse all the pages on a site - but this is really up to the owner of the site, and how accessible they make it.
If the site does not want you to do this, there is nothing you can do to work around it. HTTP does not provide any standard mechanism for listing the contents of a directory.
You would need to hack the server sorry.
What you can do is that, if you own the domain www.my-domain.com, you can put a PHP file there, that you use as a request on demand file. That php file you will need to code some sort of code in that can look at the Folders FTP Wise. PHP can connect to a FTP server, so thats a way to go :)
http://dk1.php.net/manual/en/book.ftp.php
You can with PHP read the dirs folders and return that as an array. Best i can do.
As you have said, you must follow all the links.
To do this, you must start by retrieving stackoverflow.com, easy: file_get_contents ("http:\\stackoverflow.com").
Then parse its contents, looking for links: <a href="question/ask">, not so easy.
You store those new URL's in a database and then parse that those after, which will give you a whole new set of URL's, parse those. Soon enough you'll have the vast majority of the site's content, including stuff like sub1.stackoverflow.com. This is called crawling, and it is quite simple to implement, although not so simple to retrieve useful information once you have all that data.
If you are only interested in one particular domain, be sure to dismiss links to external sites.
No, not the way you are asking.
However, provided you have a clear goal in mind, you may be able to:
use a "primary" request to get the objects of interest. Some sites provide JSON, XML, ... apis to list such objects (e.g SO can list questions this way). Then use "per-object" requests to fetch information specific to one object
fetch information from other open (or paid) sources, e.g. search engines, directories, "forensic" tools such as SpyOnWeb
reverse engineer the structure of the site, e.g. you know that /item/<id> gets you to the page of item whose ID is <id>
ask the webmaster
Please note that some of these solutions may be in violation of the site's termes of use. Anyway these are just pointers, on top of my head.
You can use WinHTTPTack/. But it is a polite not to hammer other peoples web sites.
I just use it to find broken links and make a snap shot.
If you do start hammering other peoples sites they will take measures. Some of them will not be nice (i.e. hammer yours).
Just be polite.
Related
Im not talking about extracting a text, or downloading a web page.
but I see people downloading whole web sites, for example, there is a directory called "example" and it isnt even linked in web site, how do I know its there? how do I download "ALL" pages of a website? and how do I protect against?
for example, there is "directory listing" in apache, how do I get list of directories under root, if there is a index file already?
this question is not language-specific, I would be happy with just a link that explains techniques that does this, or a detailed answer.
Ok so to answer your questions one by one; how do you know that a 'hidden' (unlinked) directory is on the site? Well you don't, but you can check the most common directory names, whether they return HTTP 200 or 404... With couple of threads you will be able to check even thousands a minute. That being said, you should always consider the amount of requests you are making in regards to the specific website and the amount of traffic it handles, because for small to mid-sized websites this could cause connectivity issues or even a short DoS, which of course is undesirable. Also you can use search engines to search for unlinked content, it may have been discovered by the search engine on accident, there might have been a link to it from another site etc. (for instance google site:targetsite.com will list all the indexed pages).
How you download all pages of a website has already been answered, essentially you go to the base link, parse the html for links, images and other content which points to a onsite content and follow it. Further you deconstruct links to their directories and check for indexes. You will also bruteforce common directory and file names.
Well you really effectively can't protect against bots, unless you limit user experience. For instance you could limit the number of requests per minute; but if you have ajax site, a normal user will also be producing a large number of requests so that really isn't a way to go. You can check user agent and white list only 'regular' browsers, however most scraping scripts will identify themselves as regular browsers so that won't help you much either. Lastly you can blacklist IPs, however that is not very effective, there is plenty of proxies, onion routing and other ways to change your IP.
You will get directory list only if a) it is not forbidden in the server config and b) there isn't the default index file (default on apache index.html or index.php).
In practical terms it is good idea not to make it easier to the scraper, so make sure your website search function is properly sanitized etc. (it doesn't return all records on empty query, it filters % sign if you are using LIKE mysql syntax...). And of course use CAPTCHA if appropriate, however it must be properly implemented, not a simple "what is 2 + 2" or couple of letters in common font with plain background.
Another protection from scraping might be using referer checks to allow access to certain parts of the website; however it is better to just forbid access to any parts of the website you don't want public on server side (using .htaccess for example).
Lastly from my experience scrapers will only have basic js parsing capabilities, so implementing some kind of check in javascript could work, however here again you'd also be excluding all web visitors with js switched off (and with noscript or similar browser plugin) or with outdated browser.
To fully "download" a site you need a web crawler, that in addition to follow the urls also saves their content. The application should be able to :
Parse the "root" url
Identify all the links to other pages in the same domain
Access and download those and all the ones contained in these child pages
Remember which links have already been parsed, in order to avoid loops
A search for "web crawler" should provide you with plenty of examples.
I don't know counter measures you could adopt to avoid this: in most cases you WANT bots to crawl your websites, since it's the way search engines will know about your site.
I suppose you could look at traffic logs and if you identify (by ip address) some repeating offenders you could blacklist them preventing access to the server.
İ want to extract data from a php forum based on keywords I entered.
İs there something ready that can do this?
Just to give example
Kadinlarkulubu.com/forum.php
Keywords ios, android
Thanks to this info I want to get date, time, message, URL of message, keyword in the message, nick of member who wrote this message.
I need to work in different forums, so I need one or more tools that will work on key big platforms like vBulletin.
You need to create your own web crawler. If you want it to work on various different platforms, you will have to create variations on that crawler.
To start, picks your favourite forum, and give it a seed page (the page where to start crawling). Tread carefully, since you may need to be logged in to be able to see posts, and if that's the case, it may not be easy to do (making a crawler that logs you in, and breaks the captcha, for example). You can also make use of the search functionality (since many forums have search URLs similar to ?q=your_tag&p=1, this could make things a lot easier.
Just check that you're on the same domain, and that you don't go into an infinite loop, other than that, you should be fine.
Expect this to be a long term project :)
The alternative would be using API, if the forum provides one, but I doubt you will be so lucky.
2 ways
The easy way is only possible if the owner of the forum provides you access to the forum API (if it has one) or the database
The extreme hard way is make a grabber that reads a forum page by page and parses the information you like to something you can use.
I'm creating a network of websites that should communicate between themselves, for example to let all of them display an article published on one of them, or display data stored in a database of another subdomain, etc...
And this all using ajax for interactivity.
Which could be the best (and simplest) way to achieve this?
I thought an ajax call could summon a php script that could call another script on another subdomain. Is it the right way?
Thanks
I don't know exactly what you want to do. If you control the sites and server you could save all your users a lot of ajax calls if you skip doing it that way and do it on the server itself.
If you display all the articles by using javascript, users without javascript won't see anything and search engines won't be able to crawl the website.. however, maybe that's what you want.
The correct design pattern for something like this is to implement a restful API that all the other sites read from..
So you have a central API on eg. http://api.example.com/
and when a server wants to display an article, he would do something on the back end to retrieve an article list.. eg.
http://api.example.com/retrieveNewestArticles
that would return eg. a json variable with a list of the newest article.. then when you want to display that article, you would call:
http://api.example.com/showArticle/58484
That's how I would do it at least.
Some people might suggest doing it by making all the websites connect directly to the same database. That's an option, a bit more messy in the long run, but will get the job done.
certainly easier than my suggestion.
Good Day all,
I have an existing site built. I was wondering, how can my site update automatically when another website updates too? This essentially means that my existing site will obtain information like Cost, Description, images from the other site upon update.
I was pondering web services but the other site doesn't have it.
Please advise!
Thanks!
If the other site doesn't have an API, your only option is page scraping, i.e. downloading the HTML and parsing it to extract the info you want.
If they have a page structure that doesn't change often, this is generally reliable.
You'd probably want to use PHP's DomDocument to extract the info.
Generally, people don't like it because badly designed tools can tax their system resources, since generating a whole HTML page is more resource intensive than generating an API response.
Page scraping is fairly widespread, though some people discourage it. It may be disallowed by the TOU of a site, possibly having legal implications. Or, your target site may have no problem with it. There are of course large businesses built on page scraping (see 'Google').
I have a community site which has around 10,000 listings at the moment. I am adopting a new url strategy something like
example.com/products/category/some-product-name
As part of strategy, I am implementing a site map. Google already has a good index of my site, but the URLs will change. I use a php framework which accesses the DB for each product listing.
I am concerned about the perfomance effects of supplying 10,000 new URLs to google, should I be?
A possible solution I'm looking at is rendering my php-outputted pages to static HTML pages. I already have this functionality elsewhere on the site. That way, google would index 10,000 html pages. The beauty of this system is that if a user arrives via google to that HTML page, as soon as they start navigating around the site, they jump straight back into the PHP version.
My problem with this method is that I would have to append .html onto my nice clean URLs...
example.com/products/category/some-product-name.html
Am I going about this the wrong way?
Edit 1:
I want to cut down on PHP and MySQL overhead. Creating the HTML pages is just a method of caching in preparation of a load spike as the search engines crawl those pages. Are there better ways?
Unless I'm missing something, I think you don't need to worry about it. I'm assuming that your list of product names doesn't change all that often -- on a scale of a day or so, not every second. The Google site-map should be read in a second or less, and the crawler isn't going to crawl you instantly after you update. I'd try it without any complications and measure the effect before you break your neck optimizing.
You shouldnt be worried about 10000 new links, but you might want to analyze your current google traffic, to see how fast google would crawl them. Caching is always a good idea (See: Memcache, or even generate static files?).
For example, i have currently about 5 requests / second from googlebot, which would mean google would crawl those 10,000 pages in a good half hour, but, consider this:
Redirect all existing links to new locations
By doing this, you assure that links already indexed by google and other search engines are almost immediatelly rewritten. Current google rank is migrated to the new link (additional links start with score 0).
Google Analytics
We have noticed that google uses Analytics data to crawl pages, that it usually wouldn't find with normal crawling (javascript redirects, logged in user content links). Chances are, google would pick up on your url change very quickly, but see 1).
Sitemap
The rule of thumb for the sitemap files in our case is only to keep them updated with the latest content. Keeping 10,000 links, or even all of your links in there is pretty pointless. How will you update this file?
It's a love & hate relationship with me and Google crawler theese days, since most used links by users are pretty well cached, but the thing google crawler crawls usually are not. This is the reason google causes 6x the load in 1/6th the requests.
Not an answer to your main question.
You dont have to append .html. You can leave the URLs as they are. If you cant find a better way to redirect to the html file (which does not have ot have an .html suffix), you can output it via PHP with readfile.
I am concerned about the perfomance effects of supplying 10,000 new URLs to google, should I be?
Performance effects on Google's servers? I wouldn't worry about it.
Performance effects on your own servers? I also wouldn't worry about it. I doubt you'll get much more traffic than you used to, you'll just get it sent to different URLs.