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This is the reference page for the HTML pre-processor GTML. It describes
all the GTML features and commands in detail. For more information about
getting GTML, see the main GTML page.
GTML features fall into four main areas, and we'll look at them
in this order:
Commands
The original syntax of GTML was stolen shamelessly from the C
language pre-processor, and has been adapted to suit Web site
management. It supports the following commands:
Command syntax
There are two ways of writing commands:
The first method is simpler, and is the recommended way of writing GTML
, if possible. However, if you're using an HTML authoring tool which complains
about GTML commands, you can use the second method to hide the
GTML commands from the tool.
#include
If you have some common text which you want inserted in more than one Web
page, put it in a separate file - say, common.txt.
Then, at the place where you want the text in each file, put the following
line:
#include "common.txt"
GTML replaces this line with the entire contents of the file
common.txt.
The name of the file can be defined in a named constant, as described next.
The directories in which the file may be looked for can be defined in a
special named constant.
#define
This is a simple way to create shorthand definitions - what we call
named constants, or macros - for your frequently-used
text. For some text which you use often - say, an e-mail address - include a
line like this:
#define MY_EMAIL gihan@pobox.com
This defines a named constant MY_EMAIL and its
value gihan@pobox.com. The value can be any text,
including spaces and HTML markup (leading spaces and tabs are ignored), as
long as it's all on one line or it's all on
multiple consecutives lines with a trailing `\' at the end of each
lines, except the last.
To use this named constant, whenever you want your e-mail address,
specify it like this:
<<MY_EMAIL>>
The double angle-brackets tell GTML to substitute this with its
definition (You can
specify your own choice of delimiters
instead of the double-angle brackets).
There are a few other things you should know about #define:
- Named constants can be set from the command line
when you run
GTML.
- Nested definition values
The value of a named constant can itself contain other named constants,
like this:
#define MAILTO <a href="mailto:<<MY_EMAIL>>">
GTML will happily do both substitutions.
Note: Definitions are evaluated at time of use, not time of
definition. This allows you to change the nested value to get a
different result. To get definitions body evaluated at time of
definition, you must use the #define! command.
- Nested definition names
If you want the name of a named constant to contain other named
constants, use #define! instead of
#define. For example, this sets the named constant
A to fred:
#define BLAH A
#define! <<BLAH>> fred
(This doesn't achieve much here, but typically the second line is in
a separate file, which is included by the file with the first line).
- Added values
If you want to add something to the definition of a named constant, use
#define+. For example, this sets the named constant
A to foobar:
#define A foo
#define+ A bar
- Undefined values
If a named constant is not defined before it's used, its value is a
blank string.
- Re-defining values
It's perfectly OK to have more than one #define for the
same named constant. You can use this to change the value of a named
constant part-way through the processing.
- Pre-defined values
GTML creates some named constants
for you automatically, such as the file name and links to the previous
and next files.
- Variables values
Sometimes the frequently-used text you want to shorthand may embed some
variable pieces. GTML allows you to specify what the pieces are which
may vary, the same way the C language preprocessor does for macros with
arguments. Parameters are enclosed in parenthesis and seperated by a
comma. For instance, this creates a shortand to make HTML links:
#define url(x,y) <a href="mailto:x">y</a>
Now the use of
<<url(<<MY_EMAIL>>,Gihan)>>
will give:
<a href="mailto:gigan@pobox.com">Gihan</a>
- Added variables values
If you add a variable valued definition with #define+, then
you add the parameter to the initial constant. For
instance, this adds a third parameter to the url macro:
#define+ url(x) <a href="http://x">Perera</a>
Now guess what the following line will give:
<<url(<<MY_EMAIL>>,Gihan,www.pobox.com/~gihan)>>
Yeah, you find:
<a href="mailto:gigan@pobox.com">Gihan</a><a href="http://www.pobox.com/~gihan">Perera</a>
If you want to use commas in your arguments you just have to
quote the complete argument with single or double
quotes.
#newdefine
This is identical to #define, except that the
definition applies only if the named constant has not been defined already. If
it has been defined, the old definition is unchanged. #newdefine!
is identical to #define! with the same exception.
#undef
Use this to remove the definition of a named constant:
If the named constant didn't exist previously, this does nothing.
#if, #ifdef, #ifndef, #elsif, #elsifdef, #elsifndef, #else, #endif
These commands are used together for conditional output:
#if <<FRED>> == foo
Process the following lines only if after substitution, the left and
right values are equal. Here if value of named constant
FRED is equal to foo.
#if foo != <<FRED>>
Process the following lines only if after substitution, the left and
right values are different. Here if value of named constant
FRED is different from foo.
#ifdef FRED
Process the following lines only if the named constant FRED
is defined.
#ifndef FRED
Process the following lines only if the named constant FRED
is not defined.
#elsif <<FRED>> == foo
If previous lines were not processed, then process the following lines
only if after substitution, the left and right values are equal.
#elsif <<FRED>> != foo
If previous lines were not processed, then process the following lines
only if after substitution, the left and right values are different.
#elsifdef FRED
If previous lines were not processed, then process the following lines
only if the named constant FRED is defined.
#elsifndef FRED
If previous lines were not processed, then process the following lines
only if the named constant FRED is not defined.
#else
The opposite effect of the most recent matching #if,
#ifdef, #ifndef, #elsif,
#elsifdef or #elsifndef.
#endif
End a block of conditional output. Every #if,
#ifdef or #ifndef must have a matching
#endif
Conditional blocks can be nested.
#timestamp
The special named constant TIMESTAMP evaluates to the current
date and time. But to use it, you must tell GTML what format to use to print
the date/time.
The format string is specified in the #timestamp statement
like this:
#timestamp $dd/$MM/$yy at $hh:$mm:$ss
The value of <<TIMESTAMP>> will then be:
8/06/96 at 11:45:03.
As you can see, certain strings (like $dd) are replaced with
values. The full set of substitution strings is as follows (everything else is
left unchanged in the format string):
| $hh | Hour (00 to 23) |
| $mm | Minute (00 to 59) |
| $ss | Seconds (00 to 59) |
| $Day | Full weekday name (Sunday to Saturday) |
| $Ddd | Short weekday name (Sun to Sat) |
| $dd | Day of the month (1 to 31) |
| $ddth | Day of the month with ordinal extension (1st to 31th) |
| $MM | Month number (1 to 12) |
| $Month | Full month name (January to December) |
| $Mmm | Short month name (Jan to Dec) |
| $yyyy | Year (e.g. 1996) |
| $yy | Short year (e.g. 96) |
Monthnames are output in English by default; but they can be output in
other languages, according to the LANGUAGE special definition.
#mtimestamp
This is identical to timestamp, except that
the time used is not the current one, but the time the file was last modified.
#literal
The command #literal ON tells GTML to stop interpreting lines
beginning with `#' as GTML commands, until the next #literal
OFF line. Defined constants are still substituted, and
entities are translated if desired.
For example, this is useful for bracketing blocks of C code, which might
have lines beginning with `#'.
#entities
The command #entities ON tells GTML to convert the
characters `<', `>' and `&' into HTML
entities so they aren't treated as part of HTML commands. Use #entities
OFF to turn off
this conversion.
This is useful for bracketing blocks of program code, which often contain
these characters.
#definechar
Basic HTML authorized characters may only be ASCII characters. Accentuated
characters are coded in HTML in a certain way. For instance the `é'
character is coded `é'. You may want to input `é'
in your source file, and have the right code used in your HTML file. This
character's translation may be defined with the #definechar
command, like in this example:
#definechar é é
Sometimes you might want to input special characters that are not available
on your keyboard, but do not want to input its HTML code (Think of the German
`ß' on an English keyboard). For instance if you want all occurrances
of `ss' in your source file to be translated into `ß', you
can use the #definechar command:
#definechar ss ß
#compress
The command #compress ON tells GTML to begin producing
compressed HTML code, i.e. stripping multiple spaces, removing newlines, HTML
comments, and all other stuff useless for an HTML browser to render a
page. This compression is done on the output file until the next #compress
OFF.
#sitemap, #toc
When you specify a hierarchy of pages in your
project file you may insert a table of contents, or site map,
of those pages, using the command #sitemap, or
#toc.
See Document hierarchy specifications for more
information on how the list is created.
GTML project files
Because GTML is most useful for managing multiple files, it's quite
common to change something in a #include'd file, and then run GTML on all
the `.gtm' files which use it.
To make this procedure easier, GTML supports a concept of a project
file. This is a simple text file with the extension `.gtp'. It
can contain:
define ...
As for #define in a source file.
define! ...
As for #define! in a source file.
define+ ...
As for #define+ in a source file.
newdefine ...
As for #newdefine in a source file.
newdefine! ...
As for #newdefine! in a source file.
undef ...
As for #undef in a source file.
timestamp ...
As for #timestamp in a source file.
mtimestamp ...
As for #mtimestamp in a source file.
if ...
ifdef ...
ifndef ...
elsif ...
elsifdef ...
elsifndef ...
else
endif
As for
#if, #ifdef, #ifndef, #elsif, #elsifdef, #elsifndef, #else, #endif
in a source file.
definechar ...
As for #definechar in a source file.
compress ...
As for #compress in a source file.
include ...
As for #include in a source file, but only on project
files.
// ...
Comment lines (the `//' must be the first characters on the line), which
are ignored. Blank lines are also ignored.
allsource
This is a shorthand way of specifying all source files from the current
directory and sub-directories (recursively).
filename alias file
This is used to make an alias to a file, so that you may use the alias,
as a defined constant, instead of the filename itself in source
files. GTML will compute the right relative path to the file in each
source file. This way you may move your files wherever you want, GTML
will be able to recreate your pages without having to modify the source
files.
filename.gtm
All other lines are names of source files, which are processed by GTML
in turn.
These files can be in other directories below the current
directory. Simply specify the file name relative to the current
directory (e.g. sub/fred/index.gtm).
The file can be a defined alias filename. In this case use it as a
filenamed constant, e.g.
filename FOO bar/foo
<<FOO>>
The file name can be followed by a level number and a title, to be
used in creating a hierarchy of documents. In
this case the file is processed after the project file has been
completely read (in order to have the complete document hirearchy).
hierarchy
This is used to process all files of the declared hierarchy so far, so
that you may process those files more than once, if you want to change
some named constant values between each process. If not used
files of the hierarchy are processed after the project file has been
entirely read.
When you run GTML with the project file as a command-line argument, it
will process all the source files in the project file. They will all inherit
the define, definechar and timestamp
values, if any, in the project file. The mtimestamp value will
change according to the modification date of the appropriate source file.
You may use a project file, but process only selected source files
(declared in the project) with the
`-F' command line argument.
Note that #define, #newdefine and
#undef commands inside a file are local to that file - they don't
carry over to the next file in the project. However, named constants defined
in the project file are inherited by all files in the project.
Document hierarchy
GTML allows you to create a hierarchy of Web pages, with links between
them. Each Web page can have a link to the previous page, the next page, or
one level up in the hierarchy. Obviously, some of these links don't apply to
some pages - GTML generates only those that apply to each page.
Describing the hierarchy
You describe the document hierarchy to GTML by listing the file names in
the project file in a certain order, with a document level and title for
each. Level 1 is for top-level documents, and 2, 3, 4, and so on are lower
levels. File names without a level have no hierarchical information attached
to them.
When GTML processes a file, it defines special named constants which can
be used in exactly the same way as other named constants.
For each file, GTML generates the named constants,
LINK_PREV,
LINK_NEXT and
LINK_UP. These correspond to the file names of the previous file,
next file and one level up in the hierarchy. In addition, it also generates
the corresponding named constants
TITLE_PREV,
TITLE_NEXT,
TITLE_UP and
TITLE_CURRENT to be the titles of these files (As stated above,
the title follows the level number in the project file).
Some of these named constants may not be applicable to some files, in which
case the named constant is not defined for that file.
Example
Here's an extract from a hypothetical GTML project file:
contents.gtm 1 Table of Contents
chapter1.gtm 2 Introduction
sec11.gtm 3 What's the Problem
sec12.gtm 3 Old Approaches
sec13.gtm 3 New Idea
chapter2.gtm 2 Historical Evidence
sec21.gtm 3 Early 1900's
sec22.gtm 3 Recent Findings
chapter3.gtm 2 Our Bright Idea
To take a simple case, the file sec21.gtm will have
LINK_NEXT set to sec22.html (and TITLE_NEXT
set to Recent Findings) and LINK_UP set to
chapter2.html (and TITLE_UP set to Historical
Evidence). LINK_PREV and TITLE_PREV will be
undefined.
Using the links
The links can be used to create navigation links between the
documents. In other words, each document can have links up the
hierarchy and to the next and previous documents.
Typically, you would place the navigation information in a common file and
#include it into each GTML source file. The GTML
#ifdef command can be used to exclude links which don't apply to
a particular file.
Here's a simple example:
#ifdef LINK_NEXT
<p>Next document: <a href="<<LINK_NEXT>>"><<TITLE_NEXT>></a>
#endif
#ifdef LINK_PREV
<p>Previous document: <a href="<<LINK_PREV>>"><<TITLE_PREV>></a>;
#endif
#ifdef LINK_UP
<p>Up one level: <a href="<<LINK_UP>>"><<TITLE_UP>></a>;
#endif
Creation of table of contents
When you have described a document hierarchy, and you use a
#toc or #sitemap command into your
source file, GTML includes a sitemap generated as a list with the help of the
__TOC_#__(x), and __TOC_#_ITEM__(x,y) special named
constants (`#' being a file level).
With the previous example it gives:
<<__TOC_1__('
<<__TOC_1_ITEM__('contents.html','Table of Contents')>>
<<__TOC_2__('
<<__TOC_2_ITEM__('chapter1.html','Introduction')>>
<<__TOC_3__('
<<__TOC_3_ITEM__('sec11.html','What's the Problem')>>
<<__TOC_3_ITEM__('sec12.html','Old Approaches')>>
<<__TOC_3_ITEM__('sec13.html','New Idea')>>
')>>
<<__TOC_2_ITEM__('chapter2.html','Historical Evidence')>>
<<__TOC_3__('
<<__TOC_3_ITEM__('sec21.html','Early 1900's')>>
<<__TOC_3_ITEM__('sec22.html','Recent Findings')>>
')>>
')>>
')>>
__TOC_#__(x), and __TOC_#_ITEM__(x,y) have
the following default values:
#define __TOC_#__(x) <ul>x</ul>
#define __TOC_#_ITEM__(x,y) <li><a href="x">y</a>
You may redefine this constant to whatever you want as long as you respect
the number of variables.
Special definitions
Environment
All environment variables are defined as named constants by GTML.
Current file names
The special named constants ROOT_PATH, BASENAME,
FILENAME and PATHNAME are set to the current
path to root of the project (where the project file resides), output file name
without any extension and excluding any directory path information, output
file name excluding any directory path information, and directory path
information relative to the path to the root of the project.
Search path for include files
GTML always searches for include files in the directory of the processed
source file first, then the current directory (where the GTML command is
executed).
In addition, if you define the named constant INCLUDE_PATH,
GTML will interpret it as a list of directories (separated by colons), to
search for include files. Those directories may be absolute, or relative to
the root path of the project.
Output directory
By default, GTML writes its output files to the same directory as the
corresponding source file. You can override this by defining the named
constant OUTPUT_DIR as the name of the output directory.
If you are doing this with a project file, specify OUTPUT_DIR
as the top-level output directory. GTML will create the same directory
hierarchy for the output files as for the input files (It creates
sub-directories as required).
Output suffix
By default all created files are created by changing the .gtm, or
.gtml extension of the source file to the .html one.
You may change this behavior by defining the special constant
EXTENSION to whatever extension you want.
The definition of this constant does not have sense in a source file, since
the output file is already created the moment GTML starts to parse the source
file. It makes sense however to define it in the
project file or on the command line.
If the suffix is preceded by two dots as in gtml.css..gtm, then the
source suffix is not replaced, but just removed, as in gtml.css.
Fast generation
GTML only processes files which are younger than the output files which
they might produce.
This is very useful, as it increases the generation speed of web
sites with a big number of pages, when only one of them has been changed. Same
kind of the way make works.
To enable this feature you just have to define the special constant
FAST_GENERATION. The use of this constant will work only in
GTML project files or on the command line.
This feature does not take into account included files, but only the main
gtml source, and the wanted output. To deal with more complex file
dependencies you may use the make tool in conjunction with the
`-F' and
`-M' command line arguments.
Language localisation
By default all timestamps produce monthnames and daynames which are output
in English. You can output them in other languages by defining the constant
LANGUAGE to a value corresponding to an available language.
As of today seven languages are available. The default one is
English. Following is the list of those language with the corresponding value
for LANGUAGE constant:
fr for French ;
de for German ;
ie for Irish ;
it for Italian ;
nl for Dutch ;
no for Norvegian ;
se for Swedish.
If you can send me month and day names in other languages, just do it, I
will integrate it in following versions of GTML.
Substitution delimiters
The default delimiters for substituting named constants are
`<<' and `>>'. You can change these to any
other strings by defining the named constants OPEN_DELIMITER and
CLOSE_DELIMITER respectively.
For example, if you had the following lines:
#define OPEN_DELIMITER {{
#define CLOSE_DELIMTER }}
#define MY_EMAIL gihan@pobox.com
then GTML substitutes MY_EMAIL when it finds the text
{{MY_EMAIL}} instead of the default
<<MY_EMAIL>>.
Document hierarchy links
As described above, GTML
defines several named constants for links between documents.
Embedded Perl code
You may embed Perl code into your GTML source file, and have the result
of the last evaluated expression inserted in your output file, with the help of
the one argument macro __PERL__.
Here is an example inserting the size of the source file:
<<__PERL__(return (stat(<<ROOT_PATH>><<BASENAME>>.".gtm"))[7];)>>
Embedded system command code
You may embed system command output into your GTML source file, with the help of
the one argument macro __SYSTEM__.
Here is an example inserting the list of files in the current directory:
<<__SYSTEM__(dir)>>
Command-line arguments
-D
When you run GTML from the command line, you can define named constants
like this:
-DMY_EMAIL=fred
This is the same as #define MY_EMAIL fred in the file.
These definitions can occur anywhere within the command-line options,
but only affect the files after them. For example, if your
command line is:
perl gtml.pl fred.gtm -DMY_EMAIL=fred bill.gtm harry.gtm
then the MY_EMAIL definition doesn't apply to
fred.gtm.
-F
When you run GTML from the command line on a project file you may want
to process only some of the files used in it. This may be very useful in
conjunction with make for page regeneration based on complex
files dependencies (induced by #include commands).
To process only one file of a project you can use the `-F'
argument followed by the name of the file to process. File to be processed
must appear, on the command line, before the project file it appears in.
Let us suppose we have this project file, called foo.gtp:
// Beginning of foo.gtp
define MAIL beaufils@lifl.fr
foo.gtm
bar.gtm
// End of foo.gtp
If you just want to regenerate the bar.html file your command
line will be:
perl gtml -Fbar.gtm foo.gtp
List of files to processed is cleared after each project file treatment.
-M
When you run GTML with the `-M' command line argument, GTML
process project and source files, but do not produce ouput files. GTML
generates a makefile ready to create output files.
If you do not specify a filename, the generated makefile is created under
the GNUmakefile name.
To specify a filename, just add it after the `-M' argument, with a
colon between the option and the file name.
-h, --help
To get a small command line usage description you can use the
`-h', or `--help' command line argument.
--silent
If you specify the `--silent' command line argument, GTML will
produce no processing information during its work.
--version
To get the version number of the GTML you are currently using you can
use the `--version' command line argument.
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