The __IfPlugin__ allows parts of a WikiPage to be executed conditionally. You can also use shorthand "If" to run it.  

This plugin has been part of JSPWiki since version 2.6 (actually, around 2.5.106 CVS).

!! Parameters:

* __group__ = '''list'''. A "|"-separated list of group names.
* __user__ = '''list'''.  A "|"-separated list of user names.
* __ip__='''list'''. A "|"-separated list of IP addresses.
* __var__='''name'''. A wiki variable.
* __page__='''name'''. A page name.
* __contains__='''regex'''. A Perl5 [regexp|RegularExpressionSyntax] pattern.
* __is__='''regex'''. A Perl5 [regexp|RegularExpressionSyntax] pattern.
* __exists__='''true|false'''. 

!! Usage

If any of them match, the body of the plugin is executed. You can negate the content by prefixing it with a "{{!}}". For example, to greet all admins, put the following in your LeftMenu:
  [{If group='Admin'

  Hello, Admin, and your mighty powers!}]

In order to send a message to everybody except Jack use
  [{If user='!Jack'

  Jack's surprise birthday party at eleven!

Note that you can't use {{"!Jack|!Jill"}}, because for Jack, {{!Jill}} matches; and for Jill, {{!Jack}} matches. These are not [regular expressions|RegularExpressionSyntax] (though they might become so in the future).

To check for page content, use
  [{If page='TestPage' contains='xyzzy'

  Page contains the text "xyzzy"}]

The difference between "{{contains}}" and "{{is}}" is that "{{is}}" is always an exact match, whereas "{{contains}}" just checks if a pattern is available.

To check for page existence, use
  [{If page='TestPage' exists='true'

  Page "TestPage" exists.}]

With the same mechanism, it's also possible to test for the existence of a variable - just use "{{var}}" instead of "page".

Another caveat is that the plugin body content is not counted towards ReferenceManager links. So any links do not appear on any reference lists. Depending on your position, this may be a good or a bad thing, though considering that the purpose of this plugin is to ''conditionally'' include the content, any links should only be counted by the ReferenceManager if the plugin test ''passed.''

In general, the content of a plugin is considered a part of the parent page. 
This means that showing the source of a page (view page source) will reveal the content of every plugin.
Actually, retrieving the source of a page does not invoke the plugin itself.

[{If user='Simon'

Secret stuff of simon
The {{Secret stuff of simon}} will only be shown on the page when Simon is logged in. However this info will be accessible to other users when they access the page source (view page source) or open the page for editing.

You can avoid this by putting the ''secret'' plugin content in another page, eg. by using the [InsertPage] plugin. This other page will then contain an {{ [[{ALLOW ... }] }} ACL to define the right security rules. 
The access to that page will always pass via the security gates of JSPWiki before revealing its content to the user.

[{If user='Simon'

[{InsertPage page=SimonsSecretStuff}]