Wikipedia:FAQ/Technical

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Note: If you're trying to get help for a specific technical problem that isn't answered by the FAQs, try asking in Wikipedia:Troubleshooting or at the village pump.

What happens if two or more people are editing the same page?

The second person (and later persons) to save the page will receive an "edit conflict" message, and the opportunity to merge their changes into the most-currently-saved version. The wiki will also check for a conflict if you are editing and do a preview of the edit. Multiple consecutive conflicts are noticed, and will generate a slightly different message. This is similar to Concurrent Versions System (CVS), a widely-used software version management system.

How do recover a password I have forgotten?

If you entered your e-mail address when you signed up, you can have a new password generated. Click on the "Log in" link in the upper-right corner. Enter your user name, and click the button near the bottom of the page called "Mail me a new password". You should receive an e-mail message with a new random password; you can use it to log in, then go ahead and change you password to something you'll remember in your preferences.

How do I report a bug?

The developers use the tracker on the Sourceforge site to keep track of bugs. For more information, see Bug reports.

How do I suggest a new feature?

Again, feature requests can be made at Sourceforge by clicking on SourceForge.

For information on using SourceForge, please see Bug reports.

If you don't report your feature request at SourceForge, then it will probably never become implemented!!!

What software is used to run Wikipedia?

We originally ran UseModWiki, a general wiki script by Clifford Adams. In January 2002, we switched to a PHP script, which in turn was completely overhauled the following July to create Wikipedia:Software Phase III.

MySQL is used for the database backend, and Apache is the web server.

The Wikipedia server's operating system is Linux.

How about the hardware?

Our database server runs on a PC that has dual Athlon MP 1800+ processors. It has 2GB of RAM and 72GB of storage on SCSI hard drives.

The web server runs on an 850 MHz Pentium III with 2GB RAM.

The current setup (August 2003) is that we've got all the databases on one server. The database server also is the web server for most languages. The web server for the English-language Wikipedia currently is on a separate machine to help lighten the load on the others and on the database.

Future plans are

to get a bigger web server to run everything on faster, and to let the database server do its job of databases only
to get a separate backup database server which can run searches and other slow-but-read-only operations to lighten the load on the main database, as well as take over if the main database server fails.

How about the connection?

To be answered

How big is the database?

The database is roughly 16 GB in size (including all languages and support tables) and growing. (You can download compressed database dumps at http://download.wikipedia.org/ )

Uploaded images and media files take another gigabyte or so.

Why are some of the pages scrunched together and capitalized LikeThis?

The original wiki standard is to treat anything scrunched together and capitalized LikeThis (sometimes called CamelCase) automatically as a link. This linking style was originally used by Wikipedia, but we now use free links. If you come across an old CamelCase link or article, you should rename (move) it to the new style, so that the CamelCase name redirects to the new title.

What kind of markup language does Wikipedia use?

Wikipedia uses a very simple markup based on UseModWiki. For more details, see Wikipedia:How does one edit a page.

Why not use HTML?

The short answer is: for simplicity and security.

And now the longer answer. Wikipedia, and wikis in general, are meant to be edited on the fly. HTML is not easy to use when you simply want to write an article. Creating links gives us a particularly dramatic example. To link to the HTML article using HTML, one would have to type

Using Wikipedia markup is much easier:

[[HTML]]

Then there's security. Different web browsers have bugs that can be exploited via HTML. Malicious users could also do things like JavaScript popup windows or page redirects if they had full HTML ability on Wikipedia. Several "experimental" sites that allowed full-HTML editing have suffered such attacks, including a couple other wikis that allowed arbitrary HTML.

So we can't use any HTML?

Alright, alright, a few tags work. Also, HTML table tags are the only way to create tables at the moment. See Wikipedia:How does one edit a page. However, there's been some rumbling among the software developers that most HTML tags are deprecated. There's also been discussion about wiki syntax for tables; see m:WikiShouldOfferSimplifiedUseOfTables for a very old beginning, and m:Wiki markup tables for more recent activity.

What about non-ASCII characters, and special symbols?

Just because the codes are defined in HTML4 doesn't mean they actually work in any common browser. See the Wikipedia:Special characters page for a detailed discussion of what is generally safe and what isn't. This page will be updated over time as more browsers come to support more features.

What about math topics, which require many special symbols, fonts, and graphics?

Just use TeX! See Wikipedia:TeX markup.

Is it possible to download the contents of Wikipedia?

Yes, the whole contents of Wikipedia can be downloaded. See Wikipedia:database download.

Note that downloading the database dumps is much preferred over trying to spider the entire site. Spidering the site will take you much longer, and puts a lot of load on the server (especially if you ignore our robots.txt and spider over billions of combinations of diffs and whatnot). Heavy spidering can lead to your spider, or your IP, being barred with prejudice from access to the site. Legitimate spiders (for instance search engine indexers) are encouraged to wait about a minute between requests, follow the robots.txt, and if possible only work during less loaded hours (2:00-14:00 UTC is the lighter half of the day).

Is there a CPAN module to query Wikipedia?

Ed Summers has written WWW::Wikipedia.

If you're just after retrieving a topic page, the following Perl sample code works. In this case, it retrieves and lists the Main Page, but modifications to the '$url variable for other pages should be obvious enough. Once you've got the page source, Perl regular expressions are your friend in finding wiki links.

 #!/usr/bin/perl
 use LWP;

 $browser = LWP::UserAgent->new();
 $url =  "http://www.wikipedia.org/wiki/Wikipedia%3AMain_Page";
 $webdoc = $browser->request(HTTP::Request->new(GET> $url));
 if ($webdoc->is_success) #...then it's loaded the page OK
 {
   print $webdoc->title, "\n\n"; # page title
   print $webdoc->content, "\n\n"; # page text
 }

Note that all (English) Wikipedia topic entries can be accessed using the conventional prefix "http://www.wikipedia.org/wiki/", followed by the topic name (with spaces turned into underscores, and special characters encoded using the standard URL encoding system).

Does wikipedia use cookies?

Cookies are not required to read or edit Wikipedia, but they are required in order to log in and link your edits to a user account.

When you log in, the wiki will set a temporary session cookie which identifies your login session; this will be expired when your browser exits (or after an inactivity timeout), and is not saved on your hard drive.

Another cookie will be saved which lists the user name you last logged in under, to make subsequent logins just a teensy bit easier. (Actually two: one with your name, and one with your account's internal ID number; they must match up.) These cookies expire after 30 days. If this worries you, clear your cookies after completing your session.

If you check the "remember my password" box on the login form, another cookie will be saved with a hash of your password (not the password itself). As long as this remains valid, you can bypass the login step on subsequent visits to the wiki. The cookie expires after 30 days, or is removed if you log out. If this worries you, don't use the option. (You should probably not use it on a public terminal!)

I have a problem not on this list, where do I go?

See Troubleshooting - if it's not on there try the village pump

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