Thursday, January 28, 2010

Scripts for fetching and testing web pages

Web pages are files (usually in HTML format) that reside on servers that accept HTTP requests from clients connected to the Internet. Browsers are software applications that send HTTP requests and display the received web pages. Using Perl, Python, or Ruby, you can automate HTTP requests. For each language, the easiest way to make an HTTP request is to use a module that comes bundled as a standard component of the language.

I've written very simple scripts, in Perl, Python, and Ruby, for fetching web files. The scripts, and an explanation of how they work, are available at:

Perl, Python and Ruby use their own external modules for HTTP transactions, and each language's module has its own peculiar syntax. Still, the basic operation is the same: your script initiates an HTTP request for a web file at a specific network address (the URL, or Uniform Resource Locator); a response is received; the web page is retrieved, if possible, and printed to the monitor. Otherwise, the response will contain some information indicating why the page could not be retrieved.

With a little effort, you can use these basic scripts to collect and examine a large number of web pages. With a little more effort, you can write your own spider software that searches for web addresses within web pages, and iteratively collects information from web pages within web pages.

© 2010 Jules J. Berman

key words: testing link, ruby programming, perl programming, python programming, bioinformatics, valid web page, web page is available, good http request, valid http request testing if web page exists, testing web links, jules berman, jules j berman, Ph.D., M.D.
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