Txt2tags User Guide

Aurelio Jargas



About

This is the txt2tags User Guide, the complete manual about the program.

Part I - Introducing Txt2tags

The First Questions You May Have

This chapter is a txt2tags overview, that will introduce the program purpose and features.

What is it?

Txt2tags is a text formatting and conversion tool.

Txt2tags converts a plain text file with markup to a number of target formats (see below for the list of targets).

Why should I use it?

You'll find txt2tags really useful if you:

And the main motivation is:

Why is it a good choice among other tools?

Txt2tags has a very straight way of growing, following basic concepts. These are the highlights:

Source File Readable Txt2tags marks are very simple, almost natural.
Target Document Readable The target document is also readable, with indentation and spacing.
Consistent Marks Txt2tags marks are simple symbols, designed to be unique enough to don't mix up with the document contents.
Consistent Rules As the marks, the rules that applies to them are tied to each other, there are no "exceptions" or "special cases".
Simple Structures All the supported formatting are simple, with no extra-options or complicated behavior modifiers. A mark is just a mark, with no options at all.
Easy to Learn With simple marks and readable source, the txt2tags learning curve is user friendly.
Nice Examples The sample files included on the package gives real life examples of documents written for txt2tags.
Valuable Tools The syntax files included on the package help you to write documents with no syntax errors.
Three User Interfaces There is a user friendly Graphical interface, a handy Web interface easy to install in intranets and a Command Line interface for power-users and scripting.
Scripting With the full featured command line mode, an experienced user can automatize tasks and do post-editing on the converted files.
Download and Run / Multi-platform Txt2tags is a single Python script. There is no need to compile it or download extra modules. So it runs nicely on *NIX, Linux, Windows and Macs.
Mature First released in 2001, txt2tags is now a mature program with years of improvements and bug fixes, extensive documentation, translations and an loyal user base.

Do I have to pay for it?

Txt2tags is free under the GPL license version 2 or later.

Supported Formatting Structures

The following is a list of all the structures supported by txt2tags.

Supported Targets

HTML

Txt2tags generates clean HTML documents, that look pretty and have its source readable. It DOES NOT use javascript, frames or other futile formatting techniques, that aren't required for simple, techie documents. But a separate CSS file can be used if wanted.

Txt2tags HTML generated code is 100% approved by the w3c validator.

SGML
It is a common document format which has powerful conversion applications (linuxdoc-tools). From a single SGML file you can generate HTML, PDF, PostScript, Info, LaTeX, LyX, RTF and XML documents. The tools also does automatic TOC and break sections into subpages.

Txt2tags generates SGML files in the LinuxDoc system type, ready to be converted with linuxdoc-tools without any extra catalog files or any SGML annoying requirements.

LATEX
The preferred academic document format, it is more powerful than you ever wondered. Full books, complicated formulas and any complex text can be written in LaTeX. But prepare to loose your hair when you try to write the tags by hand...

Txt2tags generates ready-to-use LaTeX files, doing all the complex escaping tricks and exceptions. The writer just need to worry about the text.

LOUT
Very similar to LaTeX in power, but with an easier syntax using "@" instead "\" and avoiding the need of braces in common situations. Its approach of everything-is-an-object makes the tagging much saner.

Txt2tags generates ready-to-use Lout files, which can be converted do PS or PDF files using the "lout" command.

MAN
UNIX man pages resist over the years. Document formats come and go, and there they are, unbeatable.

There are other tools to generate man documents, but txt2tags has one advantage: one source, multi targets. So the same man page contents can be converted to an HTML page, Wiki document and plain text.

MGP
MagicPoint is a very handy presentation tool (hint: Microsoft PowerPoint), that uses a tagged language to define all the screens. So you can do complex presentations in vi/emacs/notepad.

Txt2tags generates a ready-to-use .mgp file, defining all the necessary headers for fonts and appearance definitions, as long as international characters support.

Txt2tags creates "diet" .mgp files: they use the Type1 fonts, so you do not need to carry TrueType fonts files with your presentation. Also, the color definitions are simple, so even on a poor color palette system (such as startx -- -bpp 8), the presentation will look pretty!

The key is: convert and use. No quick fixes or requirements needed.

WIKI
You've heard about the Wikipedia, right? So you don't need to learn yet-another markup syntax. Just stick with txt2tags and let it convert your text to the Wikipedia format, called MediaWiki.

GWIKI
Now you can easily paste your project's current documentation into the Google Code Wiki.

DOKU
DokuWiki is a standards compliant, simple to use Wiki, mainly aimed at creating documentation of any kind. It is targeted at developer teams, workgroups and small companies. It has a simple but powerful syntax which makes sure the data files remain readable outside the Wiki and eases the creation of structured texts. All data is stored in plain text files - no database is required.

MOIN
You don't know what MoinMoin is? It is a WikiWiki!

Moin syntax is kinda boring when you need to keep {{{'''''adding braces and quotes'''''}}}, so txt2tags comes with the simplified marks and unified solution: one source, multi targets.

TXT
TXT is text. Simple, pure, beautiful.

Although txt2tags marks are very intuitive and discrete, you can remove them by converting the file to pure TXT.

The titles are underlined, and the text is basically left as is on the source.

Tip: Use the --targets command line option to get a complete list of all the available targets.

Status of Supported Structures by Target

Structure html sgml dbk tex lout man mgp creole wiki gwiki pmw doku moin adoc txt
headers Y Y Y Y Y Y Y - - - Y - - - Y
section title Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
paragraphs Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
bold Y Y Y Y Y Y Y Y Y Y Y Y Y Y -
italic Y Y Y Y Y Y Y Y Y Y Y Y Y Y -
underline Y - Y Y Y - Y - Y - Y Y Y N -
strike Y N N Y - - - - Y Y Y Y Y N -
monospaced font Y Y Y Y Y - Y - Y Y Y Y Y Y -
verbatim line Y Y Y Y Y Y Y Y Y Y Y Y Y Y -
verbatim area Y Y Y Y Y Y Y Y Y Y Y Y Y Y -
quoted area Y Y Y Y Y Y Y Y Y Y Y Y Y N Y
internet links Y Y Y - - - - Y Y Y Y Y Y Y -
e-mail links Y Y Y - - - - Y Y Y Y Y Y Y -
local links Y Y Y N N - - N N N Y Y Y N -
named links Y Y Y - - - - Y Y Y Y Y Y Y -
bulleted list Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
numbered list Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y
definition list Y Y Y Y Y Y N Y Y - Y - Y N Y
horizontal line Y - N Y Y - Y Y Y - Y Y Y N Y
image Y Y Y Y Y - Y Y Y Y Y Y Y Y -
table Y Y N Y N Y N Y Y Y Y Y Y N N
Extras html sgml dbk tex lout man mgp creole wiki gwiki pmw doku moin adoc txt
image align Y N N N Y - Y N Y - N Y N N -
table cell align Y Y N Y N Y N N N - N - Y N N
table column span Y N N Y N N N N N - N - N N N
Legend
Y Supported
N Not supported (may be in future releases)
- Not supported (can't be done on this target)

Command Line Interface

Please use txt2tags --help to see the command line options.

Examples:

Convert to HTML $ txt2tags -t html file.t2t
The same, using redirection $ txt2tags -t html -o - file.t2t > file.html
.
Including Table Of Contents $ txt2tags -t html --toc file.t2t
And also, numbering titles $ txt2tags -t html --toc --enum-title file.t2t
.
One liners from STDIN $ echo -e "\n**bold**" | txt2tags -t html --no-headers -

Part II - Install

Just download the program and run it on your machine.

Download & Install Python

First of all, you must download and install Python on your system.

Note that Python is already installed by default in Linux and Mac systems. If you're using those, you're done, just skip this step.

If you are not sure if you have Python or not, open a console (tty, xterm, MSDOS, Terminal.app) and type python. If it is not installed, the system will tell you.

Download txt2tags

The official location for txt2tags distribution is on the program site, at http://txt2tags.org. Just download and uncompress the package (.tgz file).

If you're in Linux, you can also use the automatic installer of your system. Some examples:

Install txt2tags

See README.md for installation instructions.

Part III - Writing and Converting Your First Document

Check the Tools

To make the first conversion you will need three things: txt2tags, a text editor and a web browser.

  1. Make sure txt2tags is installed and running on your system.

  2. Open the text editor your are comfortable with. Create a brand new empty document to be your first txt2tags one and remember to save it as plain text.

  3. Launch your favorite web browser to see the results of the conversion.

Write the Document Header

  1. Go to the text editor and on the very first line type the document main title: My First Document
  2. On the second line make a subtitle, inserting this text: A txt2tags test
  3. Then, on the third line, put some time information: Sunday, 2004

If everything went right, you should be seeing a three line document with this contents:

  My First Document
  A txt2tags test
  Sunday, 2004

This is just a part of the document, but we can already convert it and check the results.

Now save this document with the name test.txt. Remember to save it as plain text. Pay attention to which folder you are saving the file, you will need to remember it soon.

The First Conversion - Command Line Interface

If you are in the Command Line Interface, move to the folder where the file was saved and type this command:

  txt2tags --target html test.txt

The option --target is followed by the "html" string, which tells the program to what format your text file will be converted. The last item is the text filename.

The results were saved to the test.html file and then the program will show you the "txt2tags wrote test.html" message. If some error occurred, read the message carefully.

Here is a sample of how it will be shown on your screen:

  prompt$ txt2tags --target html test.txt
  txt2tags wrote test.html
  prompt$

Check the Results

Open the test.html file on the web browser to check if everything is ok.

Here it is! You just typed three simple lines of text and txt2tags made all the work to set the HTML page heading information, text alignment, sizes, spacing and appearance. See that the main title is also placed at the browser title bar.

You write text, txt2tags does the rest ;)

Tip: You can also use CSS files on HTML pages generated by txt2tags, so the page appearance is 100% configurable.

Writing the Document Body

Now back to the text editor, the next step is to type the document contents. You can write plain text as you normally do on email messages. You will see that txt2tags recognizes paragraphs and list of items automatically, you don't have to "mark" them.

Then again: save it, convert and check the results. This is the development cycle of a document in txt2tags. You just focus on the document contents, finishing documents faster than other editors. No mouse clicking, no menus, no windows, no distraction.

Considering the following contents for the test.txt file, which is only plain text, compare the generated HTML page:

  My First Document
  A txt2tags test
  Sunday, 2004
  
  Well, let's try this txt2tags thing.
  I don't know what to write.
  
  Mmmmmm, I know what I need to do now:
  - Take a shower
  - Eat a pizza
  - Sleep

You can write a full homepage with 0% of HTML knowledge. You don't need to insert any tags. And more, the same text file can be converted to any of the other txt2tags supported formats.

Besides plain text, txt2tags has some very simple marks, that you'll use when you need some other formatting or structures like bold, italic, title, images, table and other. As a quick sample, **stars for bold** and == equals for title ==. You can learn the marks on the Txt2tags Markup Demo.

Part IV - Mastering Txt2tags Concepts

The .t2t document Areas

Txt2tags marked files are divided in 3 areas. Each area has its own rules and purpose. They are:

Header Area
Place for Document Title, Author, Version and Date information.
Config Area
Place for general Document Settings and Parser behavior modifiers.
Body Area
Place for the Document Content.

All areas are optional. You can write a txt2tags document with just headers (such as our first example), or a document with no headers or settings.

The areas are delimited by special rules, which will be seen in detail on the next chapter. For now, this is a representation of the areas on a document:

               ____________
              |            |
              |   HEADERS  |       1. First, the Headers
              |            |
              |   CONFIG   |       2. Then the Settings
              |            |
              |    BODY    |       3. And finally the Document Body,
              |            |
              |    ...     |          which goes until the end
              |    ...     |
              |____________|
  

In short, this is how the areas are defined:

Headers First 3 lines of the file, or the first line blank for No Headers.
Config Begins right after the Header (4th or 2nd line) and ends when the Body Area starts.
Body The first valid text line (not comment or setting) after the Header Area.

Full Example

  My nice doc Title
  Mr. John Doe
  My Date
  
  %!target  : html
  %!style   : fancy.css
  %!options : --toc --enum-title
  
  Hi! This is my test document.
  Its content will end here.

Header Area

Location:

The Header Area is the only one that has a fixed position, line oriented. They are located at the first three lines of the source file.

These lines are content-free, with no static information type needed. But the following is recommended:

Keep in mind that the first 3 lines of the source document will be the first 3 lines on the target document, separated and with high contrast to the text body (i.e. big letters, bold). If paging is allowed, the headers will be alone and centralized on the first page.

Less (or None) Header lines

Sometimes the user wants to specify less than three lines for headers, giving just the document title and/or date information.

Just let the 2nd and/or the 3rd lines empty (blank) and this position will not be placed at the target document. But keep in mind that even blanks, these lines are still part of the headers, so the document body must start after the 3rd line anyway.

The title is the only required header (the first line), but if you leave it blank, you are saying that your document has no headers. So the Body Area will begin right after, on the 2nd line.

No headers on the document is often useful if you want to specify your own customized headers after converting. The command line option --no-headers is usually required for this kind of operation.

Straight to the point

In short: "Headers are just positions, not contents"

Place one text on the first line, and it will appear on the target's first line. The same for 2nd and 3rd header lines.

Config Area

Location:

The Config Area is optional. An average user can write lots of txt2tags files without even know it exists, but the experienced users will enjoy the power and control it provides.

The Config Area is used to store document-specific settings, so you don't have to type them on the command line when converting the document. For example, you can set the default document target type.

Please read the Settings section for more information about them.

Body Area

Location:

The body is anything outside Headers and Config Areas.

The body holds the document contents and all formatting and structures txt2tags can recognize. Inside the body you can also put comments for TODOs and self notes.

You can use the --no-headers command line option to convert only the document body, suppressing the headers. This is useful to set your own headers on a separate file, then join the converted body.

Settings

Settings are special configurations placed at the source document's Config Area that can affect the conversion process. Their syntax is:

  %! keyword : value

List of valid keywords:

Keyword Description
Target Set the default target to the document be converted to.
Options Set the default options to be used on the conversion. The format is the same as the command line options.
Style Set the document style. Used to define a CSS file for HTML/XHTML and to load a package in LaTeX.
PreProc Input filter. Sets "find and replace" rules to be applied on the Body Area of the source document.
PostProc Output filter. Sets "find and replace" rules to be applied on the converted document.

Example:

  %!target  : html
  %!options : --toc
  %!style   : fancy.css
  %!preproc : "AMJ"        "Aurelio Marinho Jargas"
  %!postproc: '<BODY.*?>'  '<BODY bgcolor="yellow">'

Note that the spacing and capitalization of the keyword are ignored. So you can also do %!Target:html and %! TARGET :html.

Learn more about settings in Part VII - Mastering Settings.

Command Line Options

The fastest way of changing the txt2tags default behavior is to use command line options.

Just like the other system's tools, the program do accept a set of predefined options. An option is an hyphen followed by a letter or two hyphens followed by one or more words, like -t and --target.

Options that are generally used are --outfile to define a customized output file name and --toc to turn on the automatic TOC generation. Most of the options can be turned off prefixing a "no-" before its name, for example: --no-toc.

You can register the desired options for a source file inside its Config Area, using the %!options setting. This way you don't have to type them on the command line anymore. Example:

  %!options: --toc -o mydoc.html

The exception is the target specification, that has its own setting:

  %!target: html

Use the --help option to get a complete list of all the options available in txt2tags.

Learn more about %!options and %!target.

User Configuration File (RC File)

The user configuration file (also called RC file) is a central place to store the settings that will be shared by ALL converted files. If you keep inserting the same settings on every .t2t file you write, move it to the RC file and it will be used globally, for existing and future source files.

The default location of this file depends on your system. It can also be specified by the user, using an environment variable.

RC file location
Windows %HOMEPATH%\_t2trc
UNIX, Linux, Mac $HOME/.txt2tagsrc
User defined T2TCONFIG variable

The format of the settings is exactly the same as the ones used on the .t2t files Config Area. There is a sample RC file on the package at doc/txt2tagsrc. Example:

  % my configs
  
  %%% Add a TOC for all targets.
  %!options: --toc

Any line that is not blank, a comment or a valid config line will raise error when txt2tags runs. So be careful when editing this file.

Txt2tags automatically apply the RC file contents into any source file it is converting. If you want to disable this behavior for a specific file, use the --no-rc command line option.

Configuration Loading Order and Precedence

There are three ways of telling txt2tags which options and settings to use, and this is the order that they are read and applied:

  1. The user configuration file (RC) settings
  2. The source document Config Area settings
  3. The command line options

First txt2tags reads the RC file contents (if any) and apply its configurations on the current source file. Then it scans the source document Config Area for settings and if found, they are applied also, overriding the RC ones in case of conflict. Finally comes the command line options, stronger than the other two.

%!include command

The include command is used to paste the contents of an external file into the source document body. It is not a config, but a command, and it is valid on the document Body Area.

The include command is useful to split a large document into smaller pieces (like chapters in a book) or to include the full contents of an external file into the document source. Sample:

  My first book
  Dr. John Doe
  1st Edition
  
  %!include: intro.t2t
  %!include: chapter1.t2t
  %!include: chapter2.t2t
  ...
  %!include: chapter9.t2t
  %!include: ending.t2t

You just inform the filename after the %!include string. The optional target specification is also supported, so this is valid either:

  %!include(html): file.t2t

Note that include will insert the file Body Area into the source document. The included file Header and Config Areas are ignored. This way you can convert the included file alone or inside the main document.

But there's another three types of include:

The Verbatim type includes a text file preserving its original spaces and formatting, just like if the text was inside the txt2tags Verbatim area (```). To specify this type, enclose the filename with backquotes:

  %!include: ``/etc/fstab``

The Raw type includes a text file as is, not trying to find and parse txt2tags marks on it, just like if the text was inside the Raw area ("""). To specify this type, enclose the filename with double quotes:

  %!include: ""nice_text.txt""

And the Tagged type is passed directly to the resulting document, with NO parsing or escaping performed by txt2tags. This way you can include additional tagged parts to your document. Useful for default header or footer information, or more complicated tagged code, unsupported by txt2tags:

  %!include(html): ''footer.html''

Note that the filename is enclosed with single quotes. As the text inserted is already parsed, you should specify the target to avoid mistakes.

%!includeconf command

The includeconf command is used to include configurations from an external file into the current one. This command is valid inside the source document Config Area only.

It is useful to share the same config for multiple files, so you can centralize it. On any file do you want to include that central configuration, put a includeconf call. Example:

  My First Document
  John Doe
  July, 2004
  
  %!includeconf: config.t2t
  
  Hi, this is my first document.

The format inside the included file is the same as in the RC file.

Note that the optional target specification is NOT supported for this command.

  %!includeconf: config.t2t            <--- OK
  %!includeconf(html): config.t2t      <--- NOT OK

Part V - Mastering Marks

Overview of all txt2tags marks:

Basic Beautifiers
Headers First 3 lines Bold **words**
Title = words = Italic //words//
Numbered title + words + Underline __words__
Paragraph words Strike --words--
Links [label url] Monospaced ``words``
Image [filename.jpg] Raw text ""words""
Tagged text ''words''
Other
Quote <TAB>words Separator line --------...
List - words Strong line ============...
Numbered list + words Table | cell1 | cell2 | cell3...
Definition list : words Anchor = title =[anchor]
Comment line % comments Comment area %%%\n comments \n%%%
Verbatim line ``` word Verbatim area ```\n lines \n```
Raw line """ words Raw area """\n lines \n"""
Tagged line ''' words Tagged area '''\n lines \n'''

General Rules:

Headers

Title, Numbered Title

Paragraph

Comment

Comment Area

Bold, Italic, Underline, Strike

Monospaced

Verbatim Line, Verbatim Area

Separator Line, Strong Line

Quote

List, Numbered List, Definition List

Image

Table

Raw, Raw Line, Raw Area

Tagged, Tagged Line, Tagged Area

Part VI - Mastering Settings

Settings are special configurations placed at the source document's Config Area that can affect the conversion process. The Settings are all optional. The average user can live fine without them. But they are addictive, if you start using them, you'll never stop :)

Setting lines are special comment lines, marked by a leading identifier ("!") that makes them different from plain comments. The syntax is just as simple as variable setting, composed by a keyword and a value, separated from each by a colon (":").

%! keyword : value

Syntax details:

Rules:

%!target

Using the target setting, a default target format is defined for the document:

  %!target: html

This way the user can just call

  $ txt2tags file.t2t

And the conversion will be done, to the specified target.

The target setting does not support optional target specification. That doesn't make sense, such as %!target(tex): html.

%!options

Writing long command lines every time you need to convert a document is boring and error prone. The Options setting let the user save all the converting options together with the source document. This also ensures that the document will always be converted the same way, with the same options.

Just write it with no syntax errors, as you were on the real command line. But omit the "txt2tags" program call on the beginning, the target specification and the source filename from the ending.

For example, if you do use this command line to convert your document:

  $ txt2tags -t html --toc --enum-title file.t2t

You can save yourself from typing pain using this Options setting inside the document source:

  %!target: html
  %!options(html): --toc --enum-title

Now the options are registered inside the source file, so you can convert it with this simple command:

  $ txt2tags file.t2t

Tip for Vim users: To convert the document right inside the editor, just run :!txt2tags %

%!preproc

The PreProc is an input filter that changes the Body Area of the source document. It is a "find and replace" feature, applied right after the line is read from the document source, before any parsing by txt2tags.

It is useful to define some abbreviations for common typed text, as:

  %!preproc: JJS          "John J. Smith"
  %!preproc: RELEASE_DATE "2003-05-01"
  %!preproc: BULLET       "[images/tiny/bullet_blue.png]"

So the user can write a line like:

  Hi, I'm JJS. Today is RELEASE_DATE.

And txt2tags will "see" this line as:

  Hi, I'm John J. Smith. Today is 2003-05-01.

This filter is a component that acts between the document author and the txt2tags conversion. It's like a first conversion before the "real" one. This behavior is similar to an external Sed/Perl filter, called this way:

  $ cat file.t2t | preproc-script.sh | txt2tags -

So the txt2tags parsing will begin after all the PreProc substitutions were applied.

Note: Remember that the preprocessing is applied only to the BODY of the source document, not including the Header Area and Config Area.

%!postproc

The PostProc is an output filter that changes the converted document. It is a "find and replace" feature, applied after all txt2tags parsing and processing is done.

It is useful to do some refinements on the generated document, change tags and add extra text or tags. Quick samples:

  %!postproc(html): '<BODY.*?>' '<BODY BGCOLOR="green">'
  %!postproc(tex) : "\\newpage" ""

These filters change the background color of the HTML page and remove the page breaks on the LaTeX target.

The PostProc rules are just like an external Sed/Perl filter, called this way:

  $ txt2tags -t html -o- file.t2t | postproc-script.sh > file.html

Before this feature was introduced, it was very common to have little scripts to "adjust" the txt2tags results. These scripts were in fact just lots of sed (or alike) commands, to do "substitute this for that" actions. Now this replacement strings can be saved together with the document text, and the plus is to use the Python powerful Regular Expression machine to find patterns.

%!style

Defining a Setting for a Specific Target

All the settings (except %!target) can be glued with a specific target using the %!key(target): value syntax. This way user can define different config for different targets.

This is specially useful in the pre/postproc filters, but is applicable to all settings. For example, defining different styles for HTML and LaTeX:

  %!style(html): fancy.css
  %!style(tex) : amssymb

For the options setting it's very useful to adjust the converted document:

  %!target: sgml
  %!options(sgml): --toc
  %!options(html): --style foo.css

In this example, the default target is Sgml and it will use TOC. If the user run txt2tags -t html file.t2t, only the HTML options will be used, so the converted file will use "foo.css" style file and will have no TOC.

Details for PreProc and PostProc Filters

Part VII - Black Magic

This chapter is really not recommended for newbies. It demonstrates how to do strange things with txt2tags filters, abusing of complex patterns and Regular Expressions.

BEWARE! The following procedures are NOT encouraged and can break things. Even some text from the document source can be lost on the conversion process, not appearing on the target document. Just use these tactics if you really need them and know what you are doing.

Note: Filters are a powerful feature, but can be dangerous!

Note: Bad filters do generate unexpected results.

Keep that in mind, please.

Inserting Multiple Lines with %!postproc (such as CSS rules)

In filters, the replacement pattern can include multiple lines using the \n line break char.

This can be handy for including really short CSS rules on HTML target, with no need to create a separate file:

  %!postproc: <HEAD>      '<HEAD>\n<STYLE TYPE="text/css">\n</STYLE>'
  %!postproc: (</STYLE>)  'body     { margin:3em               ;} \n\1'
  %!postproc: (</STYLE>)  'a        { text-decoration:none     ;} \n\1'
  %!postproc: (</STYLE>)  'pre,code { background-color:#ffffcc ;} \n\1'
  %!postproc: (</STYLE>)  'th       { background-color:yellow  ;} \n\1'

All the filters are tied to the first one, by replacing a string that it has inserted. So a single "<HEAD>" turns to:

  <HEAD>
  <STYLE TYPE="text/css">
  body     { margin:3em               ;}
  a        { text-decoration:none     ;}
  pre,code { background-color:#ffffcc ;}
  th       { background-color:yellow  ;}
  </STYLE>

Creating "Target-Specific" Contents with %!preproc

Sometimes you need to insert some text on a specific target, but not on the others. This kind of strange behavior can be done using some PreProc tricks.

The idea is to insert this extra text on the document source as comments, but mark it in a way that a target-specific filter will "uncomment" those lines.

For example, if an extra paragraph must be added only in HTML target. Place the text as special comments, like this:

  %html% This HTML page is Powered by [txt2tags http://txt2tags.org].
  %html% See the source TXT file [here source.t2t].

As those lines start with %, they are plain comments lines and will be ignored. But when adding this special filter:

  %preproc(html): '^%html% ' ''

The leading string is removed and those lines will be "activated", not being comments anymore. As a explicit target config, this filter will be processed for HTML targets only.

Changing Txt2tags Marks with %!preproc

Being a Regular Expressions guru, the user can customize the document source syntax, changing the txt2tags default marks to some he find more comfortable.

For example, a leading TAB is the Quotation mark. If the user doesn't like it, or his text editor has some strange relationship with TABs, he can define a new mark for Quoted text. Say a leading ">>> " was his choice. Then he will do this simple filter:

  %!preproc: '^>>> ' '\t'

And on the document source, the quoted text will be something like:

  >>> This is a quoted text.
  >>> The user defined this strange mark.
  >>> But they will be converted to TABs by PreProc.

Before the parsing begins, the strange ">>> " will be converted to TABs and txt2tags will recognize the Quote mark.

BEWARE! Extreme PreProc rules could eventually change the entire marks syntax, even generating conflicts between marks. Be really really careful when doing this.

The End

Thanks for reading! :)

http://txt2tags.org

(see source)