TWiki Webmaster Reference (ver. 01 Sep 2001)

This page contains all documentation topics as one long and complete reference sheet. Use the extended menu below to jump directly to sections. Doubleclick anywhere on-screen to return to the top of the page.

(You can also browse the TWiki reference as individual pages from the full topics menu.)

Note: Read the most up to date version of this document at http://TWiki.org/cgi-bin/view/TWiki/TWikiDocumentation

Related Topics: TWikiSite, TWikiHistory, TWikiPlannedFeatures, TWikiEnhancementRequests

TWiki System Requirements

Server and client system requirements for TWiki 01-Sep-2001

Overview

Maintaining minimum client and server requirements is necessary to keep TWiki deployment as broad as possible.

Server Requirements

TWiki is written in Perl 5, uses a number of shell commands, and requires RCS (Revision Control System), a GNU Free Software package. TWiki is developed in a basic Linux/Apache environment. It also works with Microsoft Windows, and should have no problem on any other platform that meets the requirements:

Current documentation covers Linux only. A TWikiOnWindows installation guide is next.

Client Requirements

The TWiki standard installation has extremely low browser requirements:

• HTML 3.2 compliant
• generates XHTML 1.0 pages that are compatible with HTML 3.2
• minimal use of JavaScript in the user interface (degrades gracefully)
• no cookies
• no CSS

You can easily add capabilities, through customizing the templates, for one, while tailoring the browser requirements to your situation.

Known Issues

• The new TWikiPlugins feature currently does not have compatibility guidelines for developers. Plugins can require just about anything: browser-specific functions, stylesheets (CSS), DHTML, Java applets, cookies.

-- MikeMannix - 15 Sep 2001

TWiki Access Control

Restricting read and write access to topics and webs, by users and groups

Overview

TWikiAccessControl allows you restrict access to single topics and entire webs, by individual user and by user groups, in three main areas: view; edit & attach; and rename/move/delete. These controls, combined with TWikiUserAuthentication, let you easily create and manage an extremely flexible, fine-grained privilege system.

An Important Control Consideration

Open, freeform editing is the essence of the WikiCulture - it's what makes TWiki different and often more effective than other collaboration tools. So, it is strongly recommended that decisions to restrict read or write access to a web or a topic are made with care. Experience shows that unrestricted write access works very well because:

• Peer influence is enough to ensure that only relevant content is posted.

• Peer editing - the ability to rearrange anything on a page - keeps topics focussed.

• All content is preserved under revision control.
  • Edits can be undone by the TWikiAdminGroup (the default administrators group; see #ManagingGroups).
  • Users are encouraged to edit and refactor (condense a long topic), since there's a safety net.

As a collaboration guideline:

• Create broad groups (more and varied input), and...
• Avoid creating view-only users (if you can read it, you can contribute to it).

Users and Groups

Access control is based on users and groups. Users are defined by their WikiNames, an then organized into unlimited combinations under different user groups.

Managing Users

A user is created by with the TWikiRegistration form. The process generates a topic in the Main web in the new user's WikiName. The default visitor name is TWikiGuest^?.

• Users can be authenticated using Basic Authentication or SSL. TWikiUserAuthentication is required in order to track user identities.

Managing Groups

Groups are defined by group topics in the Main web, like the TWikiAdminGroup. To start a new group:

1. Create a new topic with A name that ends in Group, SomeGroup
2. Define two variables:
   • Set GROUP = < list of users and groups >
   • Set ALLOWTOPICCHANGE = < list of users and groups >

• GROUP is a comma-separated list of users and of other groups:
      Set GROUP = Main.SomeUser, Main.OtherUser, Main.SomeOtherGroup

• ALLOWTOPICCHANGE defines who is allowed to change the group topic; it is a comma delimited list of users and groups. You typically want to restrict that to the members of the group itself, so it should contain the name of the topic,
      Set ALLOWTOPICCHANGE = Main.TWikiAdminGroup
  for the TWikiAdminGroup topic. (This prevents users not in the group from editing the topic and from gaining unauthorized membership to the group.)

Restricting Write Access

You can define who is allowed to make changes to a web or a topic.

Deny Editing by Topic

Denying editing of a topic also restricts attaching files to it; both privileges are assigned together.

• Define one or both of these variables in a topic, preferably at the end of the page:
  • Set DENYTOPICCHANGE = < list of users and groups >
  • Set ALLOWTOPICCHANGE = < list of users and groups >

• DENYTOPICCHANGE defines users or groups that are not allowed to make changes to the topic. It is a comma delimited list of users and groups. Example:
      * Set DENYTOPICCHANGE = Main.SomeBadBoy, Main.SomeBadGirl, Main.SomeHackerGroup

• ALLOWTOPICCHANGE defines users or groups that are allowed to make changes to the topic. It is a comma delimited list of users and groups. Example:
      * Set ALLOWTOPICCHANGE = Main.SomeGoodGuy, Main.SomeGoodGirl, Main.TWikiAdminGroup

• DENYTOPICCHANGE is evaluated before ALLOWTOPICCHANGE. Access is denied if the authenticated person is in the DENYTOPICCHANGE list, or not in the ALLOWTOPICCHANGE list. Access is granted in case DENYTOPICCHANGE and ALLOWTOPICCHANGE is not defined.

Deny Editing by Web

Restricting web-level editing blocks creating new topics, changing topics or attaching files.

• Define one or both of these variable in the WebPreferences topic:
  • Set DENYWEBCHANGE = < list of users and groups >
  • Set ALLOWWEBCHANGE = < list of users and groups >

The same rules apply as for restricting topics, with these additions:

• DENYTOPICCHANGE (in topic) overrides DENYWEBCHANGE (in WebPreferences)
• ALLOWTOPICCHANGE (in topic) overrides ALLOWWEBCHANGE (in WebPreferences)

Restricting Rename Access

You can define who is allowed to rename, move or delete a topic, or rename a web.

Deny Renaming by Topic

To allow a user to rename, move or delete a topic, they also need write (editing) permission. They also need write access to change references in referring topics.

• Define one or both of these variables in a topic, preferably at the end of the topic:
  • Set DENYTOPICRENAME = < list of users and groups >
  • Set ALLOWTOPICRENAME = < list of users and groups >

• DENYTOPICCRENAME defines users or groups that are not allowed to rename the topic. It is a comma delimited list of users and groups. Example:
      * Set DENYTOPICRENAME = Main.SomeBadBoy, Main.SomeBadGirl, Main.SomeHackerGroup

• ALLOWTOPICRENAME defines users or groups that are allowed to rename the topic. It is a comma delimited list of users and groups. Example:
      * Set ALLOWTOPICRENAME = Main.SomeGoodGuy, Main.SomeGoodGirl, Main.TWikiAdminGroup

• DENYTOPICRENAME is evaluated before ALLOWTOPICRENAME. Access is denied if the authenticated person is in the DENYTOPICRENAME list, or not in the ALLOWTOPICRENAME list. Access is granted in case DENYTOPICRENAME and ALLOWTOPICRENAME is not defined.

Deny Renaming by Web

You can define restrictions of who is allowed to rename a netfrag.org web.

• Define one or both of these variable in the WebPreferences topic:
  • Set DENYWEBRENAME = < list of users and groups >
  • Set ALLOWWEBRENAME = < list of users and groups >

The same rules apply as for topics, with these additions:

• DENYTOPICRENAME (in topic) overrides DENYWEBRENAME (in WebPreferences)
• ALLOWTOPICRENAME (in topic) overrides ALLOWWEBRENAME (in WebPreferences)

Restricting Read Access

You can define restrictions of who is allowed to view a netfrag.org web.

• Define one or both of these variable in the WebPreferences topic:
  • Set DENYWEBVIEW = < list of users and groups >
  • Set ALLOWWEBVIEW = < list of users and groups >

Known Issues

• The view restriction is not suitable for very sensitive content since there is a way to circumvent the read access restriction.
• Read access restriction only works if the view script is authenticated, that means that users need to log on also just to read topics. TWikiInstallationGuide has more on Basic Authentication based on the .htaccess file.

Selective Unrestricted Web Access

• There is a workaround if you prefer to have unrestricted access to view topics located in normal webs, and to authenticate users only for webs where view restriction is enabled:
  1. Omit the view script from the .htaccess file.
  2. Enable the $doRememberRemoteUser flag in lib/TWiki.cfg as described in TWikiUserAuthentication. netfrag.org will now remember the IP address of an authenticated user.
  3. Copy the view script to viewauth (or better, create a symbolic link)
  4. Add viewauth to the list of authenticated scripts in the .htaccess file.
     • When a user accesses a web where you enabled view restriction, netfrag.org will redirect from the view script to the viewauth script once (this happens only if the user has never edited a topic). Doing so will ask for authentication. The viewauth script shows the requested topic if the user could log on and if the user is authorized to see that web.
     • If you enable view restriction for a web, it is recommended to restrict search "all webs" from searching this web. Enable this restriction with the NOSEARCHALL variable in its WebPreferences, like:
       • Set NOSEARCHALL = on
     • It is not recommended to restrict view access to individual topics since all content is searchable within a web.

Hiding Control Settings

• To hide access control settings from normal browser viewing, place them in comment markers.

<!--
Set DENYTOPICCHANGE = Main.SomeGroup
-->

The SuperAdminGroup

By mistyping a user or group name in the ALLOWTOPICCHANGE setting, it's possible to lock a topic so that it no-one can edit it from a browser. To avoid this:

• Set the $superAdminGroup variable in lib/TWiki.cfg to the name of a group of users that are always allowed to edit/view topics.

$superAdminGroup = "TWikiAdminGroup";

• The default setting is not to have superusers.

-- MikeMannix^? - 02 Dec 2001

TWiki Templates

Definition of the templates used to render all HTML pages displayed in TWiki

Overview

The new modular template system offers flexible, easy control over the layout of all TWiki pages. The master template approach groups parts that are shared by several templates - like headers and footers - in a common file. Special variables allow individual layouts to include parts from a master template - variables are mixed with regular HTML mark-up for template-specific content. Templates are used to define page layout, and also to supplydefault content for new pages.

Major changes from the previous template system

Where the old templates were each complete HTML documents, the new templates are defined using variables to include template parts from a master file. You can now change one instance of a common element to update all occurrences; previously, every affected template had to be updated. This simplifies the conversion of templates into XHTML format, and provides a more versatile solution for templates and for TWikiSkins. The new system:

• separates a set of common template parts into a base template that is included by all of the related templates;
• defines common variables, like a standard separator (ex: "|"), in the base template;
• defines variable text in the individual templates and passes it back to the base template.

Functional Specifications

• Special template directives (or preprocessor commands) are embedded in normal templates.
• Use of template directives is optional, templates work without them.
• All template preprocessing is done in &TWiki::Store::readTemplate() so that the caller simply gets an expanded template file (the same as before).
• Directives are of the form %TMPL:<key>% and %TMPL:<key>{"attr"}%.
• Directives:
  • %TMPL:INCLUDE{"file"}%: Includes a template file. The template directory of the current web is searched first, then the templates root (twiki/templates).
  • %TMPL:DEF{"var"}%: Define a variable. Text between this and the END directive is not returned, but put into a hash for later use.
  • %TMPL:END%: Ends variable definition.
  • %TMPL:P{"var"}%: Prints a previously defined variable.
• Variables are live in a global name space, there is no parameter passing.
• Two-pass processing, so that you can use a variable before declaring it or after.
• Templates and TWikiSkins work transparently and interchangeably. For example, you can create a skin that overloads just the twiki.tmpl, like twiki.print.tmpl, that redefines the header and footer.
• NOTE: The template directives work only for templates, they do not get processed in topic text.

TWiki Master Template

All common parts are defined in a master template, twiki.tmpl, that all other templates use.

Template variable:	Defines:
%TMPL:DEF{"sep"}%	"|" separator
%TMPL:DEF{"htmldoctype"}%	Start of all HTML pages
%TMPL:DEF{"standardheader"}%	Standard header (ex: view, index, seach)
%TMPL:DEF{"simpleheader"}%	Simple header with reduced links (ex: edit, attach, oops)
%TMPL:DEF{"standardfooter"}%	Footer, excluding revision and copyright parts
%TMPL:DEF{"oops"}%	Skeleton of oops dialog

Types of Template

There are two types of templates:

• HTML Page Templates: Defines layout of netfrag.org pages
• Template Topics: Defines default text when you create a new topic

HTML Page Templates

netfrag.org uses HTML template files for all actions like topic view, edit, preview and so on. This allows you to change the look and feel of all pages by editing just some template files.

The template files are in the twiki/templates directory. As an example, twiki/templates/view.tmpl is the template file for the twiki/bin/view script. Templates can be overloaded per web. The following search order applies:

1. twiki/templates/$webName/$scriptName.tmpl
2. twiki/templates/$scriptName.tmpl

Note: $webName is the name of the web (ex: Main), and $scriptName is the script (ex: view).

Note: TWikiSkins can be defined to overload the standard templates.

Special variables are used in templates, especially in view, to display meta data.

Template Topics

Template topics define the default text for new topics. There are three types of template topics:

Topic Name:	What it is:
WebTopicViewTemplate	Help text shown when you view a non existing topic.
WebTopicNonWikiTemplate	Help text shown when you view a non existing topic that has not a WikiName.
WebTopicEditTemplate	Default text shown when you create a new topic.

1. The topic name specified by the templatetopic CGI parameter.
2. WebTopicEditTemplate in the current web.
3. WebTopicEditTemplate in the TWiki web.

Template Topics in Action

Here is an example for creating new topics based on a specific template topic:

Above form asks for a topic name. A hidden input tag of name "templatetopic" specifies the ExampleTopicTemplate as the template topic. Here is the HTML source of the form:

<form name="new" action="%SCRIPTURLPATH%/edit%SCRIPTSUFFIX%/%WEB%/">
   * New example topic: 
     <input type="text" name="topic" value="ExampleTopic%SERVERTIME{$yearx$mox$day}%" size="23" />
     <input type="hidden" name="templatetopic" value="ExampleTopicTemplate" />
     <input type="hidden" name="onlywikiname" value="on" />
     <input type="submit" value="Create" />
     (date format is <nop>YYYYxMMxDD)
</form>

The "onlywikiname" parameter enforces WikiWords for topic names.

Note: Use can use the %WIKIUSERNAME% and %DATE% variables in your topic templates as the signature; those variables are expanded when a new topic is created. The standard topic signature is:
-- %WIKIUSERNAME% - %DATE%

Templates by Example

Attached is an example of an oops base template oopsbase.tmpl and a example oops dialog oopstest.tmpl which is based on the base template. NOTE: This isn't the release version, just a quick, simple demo.

Base template oopsbase.tmpl

The first line declares the delimiter variable called "sep", used to separate multiple link items. The variable can be called anywhere by writing %TMPL:P{"sep"}%

%TMPL:DEF{"sep"}% | %TMPL:END% <html> <head> <title> %WIKITOOLNAME% . %WEB% . %TOPIC% %.TMPL:P{"titleaction"}%</title> <base href="%SCRIPTURL%/view%SCRIPTSUFFIX%/%WEB%/%TOPIC%"> <meta name="robots" content="noindex"> </head> <body bgcolor="#FFFFFF"> <table width="100%" border="0" cellpadding="3" cellspacing="0"> <tr> <td bgcolor="%WEBBGCOLOR%" rowspan="2" valign="top" width="1%"> <a href="%WIKIHOMEURL%"> <img src="%PUBURLPATH%/wikiHome.gif" border="0"></a> </td> <td> <b>%WIKITOOLNAME% . %WEB% . </b><font size="+2"> <B>%TOPIC%</b> %TMPL:P{"titleaction"}%</font> </td> </tr> <tr bgcolor="%WEBBGCOLOR%"> <td colspan="2"> %TMPL:P{"webaction"}% </td> </tr> </table> --- ++ %TMPL:P{"heading"}% %TMPL:P{"message"}% <table width="100%" border="0" cellpadding="3" cellspacing="0"> <tr bgcolor="%WEBBGCOLOR%"> <td valign="top"> Topic <b>%TOPIC%</b> . { %TMPL:P{"topicaction"}% } </td> </tr> </table> </body>

Test template oopstest.tmpl

Each oops template basically just defines some variables and includes the base template that does the layout work.

%TMPL:DEF{"titleaction"}% (test =titleaction=) %TMPL:END% %TMPL:DEF{"webaction"}% test =webaction= %TMPL:END% %TMPL:DEF{"heading"}% Test heading %TMPL:END% %TMPL:DEF{"message"}% Test =message=. Blah blah blah blah blah blah blah blah blah blah blah... * Some more blah blah blah blah blah blah blah blah blah blah... * Param1: %PARAM1% * Param2: %PARAM2% * Param3: %PARAM3% * Param4: %PARAM4% %TMPL:END% %TMPL:DEF{"topicaction"}% Test =topicaction=: [[%WEB%.%TOPIC%][OK]] %TMPL:P{"sep"}% [[%TWIKIWEB%.TWikiRegistration][Register]] %TMPL:END% %TMPL:INCLUDE{"oopsbase"}%

Sample screen shot of oopstest.tmpl

With URL: .../bin/oops/Test/TestTopic2?template=oopstest&param1=WebHome&param2=WebNotify

Known Issues

• A drawback of referring to a master template is that you can only test a template from within TWiki, where the include variables are resolved. In the previous system, each template is a structurally complete HTML document with a .tmpl filename extension - it contains unresolved %VARIABLES%, but can still be previewed directly in a browser.

-- PeterThoeny - 23 Jul 2001
-- MikeMannix - 14 Sep 2001

TWiki Skins

Skins overlay regular templates with alternate header/footer layouts; topic text is not affected

Overview

Skins are customized TWikiTemplates files. You can use skins to change the look of a netfrag.org topic, for example, the layout of the header and footer. Rendered text between header and footer does not change. You can also use skins to define an alternate view, like a view optimized for printing.

Defining Skins

Skin files are located in the twiki/templates directory and are named with the syntax: <scriptname>.<skin>.tmpl. For example, the Printable skin for the view template is view.print.tmpl.

Activating Skins

A skin can be activated in two ways:

• Define the SKIN Preference variable in TWikiPreferences, one of the WebPreferences, or in a user - TWikiGuest^? - topic.
  • Set SKIN = print

• Add ?skin=name to the URL, for this example:
  • https://netfrag.org/twiki/bin/view/TWiki/TWikiSkins?skin=print (for the print view skin)
  • https://netfrag.org/twiki/bin/view/TWiki/TWikiSkins?skin=plain (for the plain view skin that has no header and footer)

The ?skin=name URL parameter overrides the SKIN Preference value.

-- PeterThoeny - 14 Jul 2001

TWiki Variables

Text strings expanded on the fly to display data or system info

Overview

TWikiVariables are text strings - %VARIABLE% - that expand into content whenever a page is opened. Variables are replaced by their actual values: stored data, or system info (like the date, or the current user). There are predefined variables, and Preference variables that you set. You can also define custom variables, with new names and values.

Predefined Variables

Most predefined variables return values that were either defined when TWiki was installed, or taken from server info (like current username, or date and time). Many of the variables let you control how the formatted results appear.

netfrag.org expands the following variables (enclosed in % percent signs):

[1] Note: The search form uses identical names for input fields.

[2] Note: A web can be excluded from a web="all" search if you define a NOSEARCHALL=on variable in its WebPreferences.

Preferences Variables

Additional variables are defined in the preferences ( site-level ( SL ) in TWikiPreferences, web-level ( WL ) in WebPreferences of each web, and user level ( UL ) preferences in individual user topics):

Setting Preferences

• The syntax for Preferences variables is the same anywhere in TWiki. In Edit mode, from the start of a new line:
  [6 spaces] * [space] Set [space] VARIABLENAME [space] = [value]
  Example:
  • Set VARIABLENAME = value

Creating Custom Variables

• You can add your own preference variables for an entire site, a single web, or a single topic, using the standard syntax. Whatever you include in your variable will be expanded on display, and treated exactly as if it had been written out. So you can place formatted text, page links, image paths.

Example: Create a custom logo variable

• To place a logo anywhere in a web by typing %MYLOGO%, simply define the variable on the web's WebPreferences page. You also have to upload logo.gif - this can be done by attaching a file to LogoTopic (any topic name you choose):
  • Set MYLOGO = %PUBURL%/%MAINWEB%/LogoTopic/logo.gif

-- PeterThoeny - 13 Sep 2001
-- MikeMannix - 30 Nov 2001

Merged into TWikiMetaData - this topic to be rolled back.

TWiki Plugins

Plug-in enhanced feature add-ons, with a Plugin API for developers

Overview

You can add Plugins to extend TWiki's functionality, without altering the core program code. A plug-in approach lets you:

• add virtually unlimited features while keeping the main TWiki code compact and efficient;
• heavily customize an installation and still do clean updates to new versions of TWiki;
• rapidly develop new TWiki functions in Perl using the Plugin API.

Everything to do with TWiki Plugins - demos, new releases, downloads, development, general discussion - is available at TWiki.org, in the TWiki:Plugins web.

Preinstalled Plugins

TWiki comes with three Plugins as part of the standard installation.

• DefaultPlugin optionally handles some legacy variables from older versions of TWiki. You can control this option from TWikiPreferences. (Perl programmers can also add rules for simple custom processing.)

• EmptyPlugin is a fully functional module, minus active code; it does nothing and serves as a template for new Plugin development.

• InterwikiPlugin is preinstalled but can be disabled or removed. Use it for shorthand linking to remote sites, ex: TWiki:Plugins expands to TWiki:Plugins on TWiki.org. You can edit the predefined set of of Wiki-related sites, and add your own.

Installing Plugins

Each TWikiPlugin comes with full documentation: step-by-step installation instructions, a detailed description of any special requirements, version details, and a working example for testing.

Most Plugins can be installed in three easy steps, with no programming skills required:

1. Download the zip file containing the Plugin, documentation, and any other required files, from TWiki:Plugins.
2. Distribute the files to their proper locations - unzip the zip archive in your TWiki installation directory - if have a standard TWiki installation, this will distribute automatically. Otherwise, place the files according to the directory paths listed on the Plugin top in TWiki:Plugins.
3. Check the demo example on the Plugin topic: if it's working, the installation was fine!

Special Requests: Some Plugins need certain Perl modules to be preinstalled on the host system. Plugins may also use other resources, like graphics, other modules, applications, templates. In these cases, detailed instructions are in the Plugin documentation.

Each Plugin has a standard release page, located in the TWiki:Plugins web at TWiki.org. In addition to the documentation topic (SomePlugin), there's a separate development page.

• Doc page: Read all available info about the Plugin; download the attached distribution files.
• Dev page: Post feature requests, bug reports and general dev comments; topic title ends in Dev (SomePluginDev).
• User support: Post installation, how to use type questions (and answers, if you have them) in the TWiki:Support web.

On-Site Pretesting

To test new Plugins on your installation before making them public, you may want to use one of these two approaches:

• Method 1: Safely test on-the-fly by creating separate Production and Test branches in your live TWiki installation.
  • Duplicate the twiki/bin and twiki/lib directories for the Test version, adjusting the paths in the new lib/TWiki.cfg, the twiki/data; the twiki/templates and twiki/pub directories are shared.
  • Test Plugins and other new features in the Test installation until you're satisfied.
    • If you modify topics using the new features, live users will likely see unfamiliar new META tags showing up on their pages - to avoid this, create and edit test-only topics to try out new features.
  • Copy the modified files to the Production installation. You can update a TWiki installation live and users won't even notice.

• Method 2: List the Plugin under Test in the DISABLEDPLUGINS variable in TWikiPreferences. Redefine the DISABLEDPLUGINS variable in the Test web and do the testing there.

Managing Plugins

When you finish installing a Plugin, you should be able to read the user instructions and go. In fact, some Plugins require additional settings or offer extra options that you have to select. Also, you may want to make a Plugin available only in certain webs, or temporarily disable it. And may want to list all available Plugins in certain topics. You can handle all of these management tasks with simple procedures.

Setting Preferences

Installed Plugins can be toggled on or off, site-wide or by web, through TWikiPreferences and individual WebPreferences:

• All Plugin modules present in the lib/TWiki/Plugins directory are activated automatically unless disabled by the DISABLEDPLUGINS Preferences variable in TWikiPreferences. You can optionally list the installed Plugins in the INSTALLEDPLUGINS Preferences variable. This is useful to define the sequence of Plugin execution, or to specify other webs than the netfrag.org web for the Plugin topics. Settings in TWikiPreferences are:
  • Set INSTALLEDPLUGINS = DefaultPlugin, ...
  • Set DISABLEDPLUGINS = EmptyPlugin, ...

Plugin execution order in TWiki is determined by searching Plugin topics in a specific sequence: First, full web.topicname name, if specified in INSTALLEDPLUGINS; next, the TWiki web is searched; and finally, the current web.

Plugin-specific settings are done in individual Plugin topics. Two settings are standard for each Plugin:

1. One line description, used to form the bullets describing the Plugins in the TextFormattingRules topic:
   • Set SHORTDESCRIPTION = Blah blah woof woof.
2. Debug Plugin, output can be seen in data/debug.txt. Set to 0=off or 1=on:
   • Set DEBUG = 0

• The settings can be retrieved as Preferences variables like %<pluginname>_<var>%, ex: %DEFAULTPLUGIN_SHORTDESCRIPTION% shows the description of the DefaultPlugin.

Listing Active Plugins

Plugin status variables let you list all active Plugins wherever needed. There are two list formats:

• The %ACTIVATEDPLUGINS% variable lists activated Plugins by name. (This variable is displayed in TWikiPreferences for debugging use.)
• The %PLUGINDESCRIPTIONS% variable displays a bullet list with a one-line description of each active Plugins. This variable is based on the %<plugin>_SHORTDESCRIPTION% Preferences variables of individual topics and is shown in TextFormattingRules.

DEMO: Automatically List Active Plugins Using Variables

Using %ACTIVATEDPLUGINS%:
On this TWiki site, the active Plugins are: DefaultPlugin, HeadlinesPlugin, InterwikiPlugin, TablePlugin, VisualConfirmPlugin.

Using %PLUGINDESCRIPTIONS%:
You can use any of these active TWiki Plugins:

• DefaultPlugin: This plugin can be used to specify some simple custom rendering rules. It also renders deprecated *_text_* as bold italic text.
• HeadlinesPlugin: Build news portals that show headline news based on RSS news feeds from news sites.
• InterwikiPlugin: Link ExternalSite:Page text to external sites based on aliases defined in the InterWikis topic.
• TablePlugin: Control attributes of tables and sorting of table columns
• VisualConfirmPlugin: Plugin for visual confirmation of new user registration.

The TWiki Plugin API

The Application Programming Interface (API) for TWikiPlugins provides the specifications for hooking into the core TWiki code from your external Perl Plugin module. The Plugin API is new to the Production version of TWiki with the 01-Sep-2001 release.

Available Core Functions

The lib/TWiki/Func.pm implements ALL official Plugin functions. Plugins should ONLY use functions published in this module.

If you use functions not in Func.pm, you run the risk of creating security holes. Also, your Plugin will likely break and require updating when you upgrade to a new version of TWiki.

• For best performance, enable only the functions you really need. NOTE: outsidePREHandler and insidePREHandler are particularly expensive.

Predefined Hooks

In addition to TWiki core functions, Plugins can use predefined hooks, or call backs, listed in the lib/TWiki/Plugins/EmptyPlugin.pm module.

• All but the initPlugin are disabled. To enable a call back, remove DISABLE_ from the function name.

Plugin Version Detection

To eliminate the incompatibility problems bound to arise from active open Plugin development, a Plugin versioning system and an API GetVersion detection routine are provided for automatic compatibility checking.

• All modules require a $VERSION='0.000' variable, beginning at 1.000.

• The initPlugin handler should check all dependencies and return TRUE if the initialization is OK or FALSE if something went wrong.
  • The Plugin initialization code does not register a Plugin that returns FALSE (or that has no initPlugin handler).

• $VERSION='1.000' is the current setting in TWiki::Plugins.pm and in the preinstalled system Plugins (DefaultPlugin, EmptyPlugin, InterwikiPlugin).

Creating Plugins

With a reasonable knowledge of the Perl scripting language, you can create new Plugins or modify and extend existing ones. Basic plug-in architecture uses an Application Programming Interface (API), a set of software instructions that allow external code to interact with the main program. The TWiki Plugin API Plugins by providing a programming interface for TWiki.

The DefaultPlugin Alternative

• DefaultPlugin can handle some outdated TWiki variables, found, for example, in sites recently updated from an old version. Settings are in DefaultPlugin topic. You can also add your own simple custom processing rules here, though in all but very simple cases, writing a new Plugin is preferable.

Anatomy of a Plugin

A basic TWiki Plugin consists of two elements:

• a Perl module, ex: MyFirstPlugin.pm
• a documentation topic, ex: MyFirstPlugin.txt

The Perl module can be a block of code that connects with TWiki alone, or it can include other elements, like other Perl modules (including other Plugins), graphics, TWiki templates, external applications (ex: a Java applet), or just about anything else it can call. In particular, files that should be web-accessible (graphics, Java applets ...) are best placed as attachments of the MyFirstPlugin topic. Other needed Perl code is best placed in a lib/TWiki/Plugins/MyFirstPlugin/ directory.

The Plugin API handles the details of connecting your Perl module with main TWiki code. When you're familiar with the Plugin API, you're ready to develop Plugins.

Creating the Perl Module

Copy file lib/TWiki/Plugins/EmptyPlugin.pm to <name>Plugin.pm. EmptyPlugin.pm contains no executable code, so it does nothing, but it's ready to be used. Customize it. Refer to the Plugin API specs for more information.

Writing the Documentation Topic

The Plugin documentation topic contains usage instructions and version details. It serves the Plugin files as FileAttachments for downloading. (The doc topic is also included in the distribution package.) To create a documentation topic:

1. Copy the Plugin topic template from EmptyPlugin. To copy the text, go to the page and:
   • click Edit
   • select all in the Edit box & copy
   • Cancel the edit
   • paste & save as a text file or new topic on your site
2. Customize the template for your Plugin; you'll probably want to post a working version on your local TWiki site.
3. Save your topic as a text file, for use in packaging and publishing your Plugin.

OUTLINE: Doc Topic Contents
Check EmptyPlugin on TWiki.org for the latest Plugin doc topic template. Here's a quick overview of what's covered:

Syntax Rules: <Describe any special text formatting that will be rendered.>"

MyFirstPlugin Settings: <Description and settings for custom Plugin %VARIABLES%, and those required by TWiki.>"

• Plugins Preferences <If user settings are needed, explain... Entering valuse works exactly like TWikiPreferences and WebPreferences: six (6) spaces and then:>"
  • Set <EXAMPLE = value added>

How-to Instructions: <Step-by-step set-up guide, user help, whatever it takes to install and run, goes here.>"

Test Example: <Include an example of the Plugin in action: if it works, the installation was a success!>"

Plugin Info: <Version, credits, history, requirements - entered in a form, displayed as a table. Both are automatically generated when you create or edit a page in the TWiki:Plugins web.>"

Packaging for Distribution

A minimum Plugin release consists of a Perl module with a WikiName that ends in Plugin, ex: MyFirstPlugin.pm, and a documentation page with the same name(MyFirstPlugin.txt).

1. Distribute the Plugin files in a directory structure that mirrors TWiki. If your Plugin uses additional files, include them ALL:
   • lib/TWiki/Plugins/MyFirstPlugin.pm
   • data/TWiki/MyFirstPlugin.txt
   • pub/TWiki/MyFirstPlugin/uparrow.gif [a required graphic]
2. Create a zip archive with the Plugin name (MyFirstPlugin.zip) and add the entire directory structure from Step 1. The archive should look like this:
   • lib/TWiki/Plugins/MyFirstPlugin.pm
   • data/TWiki/MyFirstPlugin.txt
   • pub/TWiki/MyFirstPlugin/uparrow.gif

Publishing for Public Use

You can release your tested, packaged Plugin to the TWiki community through the TWiki:Plugins web. All Plugins submitted to TWiki.org are available for download and further development in TWiki:Plugins. Publish your Plugin in three steps:

1. Post the Plugin documentation topic in the TWiki:Plugins web:
   • create a new topic using the Plugin name, ex: MyFirstPlugin.txt
   • paste in the topic text from Creating Plugin Documentation and save
2. Attach the distribution zip file to the topic, ex: MyFirstPlugin.zip
3. Link from the doc page to a new, blank page named after the Plugin, and ending in Dev, ex: MyFirstPluginDev. This is the discussion page for future development. (User support for Plugins is handled in TWiki:Support.)

-- AndreaSterbini - 29 May 2001
-- PeterThoeny - 14 Sep 2001
-- MikeMannix - 03 Dec 2001