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# NAME

Template::Manual::Filters - Standard filters

# DESCRIPTION

This section lists all the standard filters distributed with the Template Toolkit for post-processing output.

# STANDARD FILTERS

## format(format)

The 'format' filter takes a format string as a parameter (as per printf()) and formats each line of text accordingly.

    [% FILTER format('<!-- %-40s -->') %]
This is a block of text filtered
through the above format.
[% END %]

output:

    <!-- This is a block of text filtered        -->
<!-- through the above format.               -->

## upper

Folds the input to UPPER CASE.

    [% "hello world" FILTER upper %]

output:

    HELLO WORLD

## lower

Folds the input to lower case.

    [% "Hello World" FILTER lower %]

output:

    hello world

## ucfirst

Folds the first character of the input to UPPER CASE.

    [% "hello" FILTER ucfirst %]

output:

    Hello

## lcfirst

Folds the first character of the input to lower case.

    [% "HELLO" FILTER lcfirst %]

output:

    hELLO

## trim

Trims any leading or trailing whitespace from the input text. Particularly useful in conjunction with INCLUDE, PROCESS, etc., having the same effect as the TRIM configuration option.

    [% INCLUDE myfile | trim %]

## collapse

Collapse any whitespace sequences in the input text into a single space. Leading and trailing whitespace (which would be reduced to a single space) is removed, as per trim.

    [% FILTER collapse %]

The   cat

sat    on

the   mat

[% END %]

output:

    The cat sat on the mat

## html

Converts the characters '<', '>' and '&' to '&lt;', '&gt;' and '&amp;', respectively, protecting them from being interpreted as representing HTML tags or entities.

    [% FILTER html %]
Binary "<=>" returns -1, 0, or 1 depending on...
[% END %]

output:

    Binary "&lt;=&gt;" returns -1, 0, or 1 depending on...

## html_entity

The html filter is fast and simple but it doesn't encode the full range of HTML entities that your text may contain. The html_entity filter uses either the Apache::Util module (which is written in C and is therefore faster) or the HTML::Entities module (written in Perl but equally as comprehensive) to perform the encoding. If one or other of these modules are installed on your system then the text will be encoded (via the escape_html() or encode_entities() subroutines respectively) to convert all extended characters into their appropriate HTML entities (e.g. converting 'é' to '&eacute;'). If neither module is available on your system then an 'html_entity' exception will be thrown reporting an appropriate message.

For further information on HTML entity encoding, see http://www.w3.org/TR/REC-html40/sgml/entities.html.

## html_para

This filter formats a block of text into HTML paragraphs. A sequence of two or more newlines is used as the delimiter for paragraphs which are then wrapped in HTML <p>...</p> tags.

    [% FILTER html_para %]
The cat sat on the mat.

[% END %]

output:

    <p>
The cat sat on the mat.
</p>

<p>
</p>

## html_break / html_para_break

Similar to the html_para filter described above, but uses the HTML tag sequence <br><br> to join paragraphs.

    [% FILTER html_break %]
The cat sat on the mat.

[% END %]

output:

    The cat sat on the mat.
<br>
<br>
Mary had a little lamb.

## html_line_break

This filter replaces any newlines with <br> HTML tags, thus preserving the line breaks of the original text in the HTML output.

    [% FILTER html_line_break %]
The cat sat on the mat.
[% END %]

output:

    The cat sat on the mat.<br>
Mary had a little lamb.<br>

## uri

This filter URI escapes the input text, converting any characters outside of the permitted URI character set (as defined by RFC 2396) into a %nn hex escape.

    [% 'my file.html' | uri %]

output:

    my%20file.html

Note that URI escaping isn't always enough when generating hyperlinks in an HTML document. The & character, for example, is valid in a URI and will not be escaped by the URI filter. In this case you should also filter the text through the 'html' filter.

    <a href="[% filename | uri | html %]">click here</a>

Indents the text block by a fixed pad string or width. The 'pad' argument can be specified as a string, or as a numerical value to indicate a pad width (spaces). Defaults to 4 spaces if unspecified.

    [% FILTER indent('ME> ') %]
blah blah blah
cabbages, rhubard, onions
[% END %]

output:

    ME> blah blah blah
ME> cabbages, rhubard, onions

## truncate(length)

Truncates the text block to the length specified, or a default length of 32. Truncated text will be terminated with '...' (i.e. the '...' falls inside the required length, rather than appending to it).

    [% FILTER truncate(21) %]
I have much to say on this matter that has previously
been said on more than one occasion.
[% END %]

output:

    I have much to say...

## repeat(iterations)

Repeats the text block for as many iterations as are specified (default: 1).

    [% FILTER repeat(3) %]
We want more beer and we want more beer,
[% END %]
We are the more beer wanters!

output:

    We want more beer and we want more beer,
We want more beer and we want more beer,
We want more beer and we want more beer,
We are the more beer wanters!

## remove(string)

Searches the input text for any occurrences of the specified string and removes them. A Perl regular expression may be specified as the search string.

    [% "The  cat  sat  on  the  mat" FILTER remove('\s+') %]

output:

    Thecatsatonthemat

## replace(search, replace)

Similar to the remove filter described above, but taking a second parameter which is used as a replacement string for instances of the search string.

    [% "The  cat  sat  on  the  mat" | replace('\s+', '_') %]

output:

    The_cat_sat_on_the_mat

## redirect(file, options)

The 'redirect' filter redirects the output of the block into a separate file, specified relative to the OUTPUT_PATH configuration item.

    [% FOREACH user = myorg.userlist %]
[% FILTER redirect("users/${user.id}.html") %] [% INCLUDE userinfo %] [% END %] [% END %] or more succinctly, using side-effect notation:  [% INCLUDE userinfo FILTER redirect("users/${user.id}.html")
FOREACH user = myorg.userlist
%]

A 'file' exception will be thrown if the OUTPUT_PATH option is undefined.

An optional 'binmode' argument can follow the filename to explicitly set the output file to binary mode.

    [% PROCESS my/png/generator
FILTER redirect("images/logo.png", binmode=1) %]

For backwards compatibility with earlier versions, a single true/false value can be used to set binary mode.

    [% PROCESS my/png/generator
FILTER redirect("images/logo.png", 1) %]

For the sake of future compatibility and clarity, if nothing else, we would strongly recommend you explicitly use the named 'binmode' option as shown in the first example.

## eval / evaltt

The 'eval' filter evaluates the block as template text, processing any directives embedded within it. This allows template variables to contain template fragments, or for some method to be provided for returning template fragments from an external source such as a database, which can then be processed in the template as required.

    my $vars = { fragment => "The cat sat on the [% place %]", };$template->process($file,$vars);

The following example:

    [% fragment | eval %]

is therefore equivalent to

    The cat sat on the [% place %]

The 'evaltt' filter is provided as an alias for 'eval'.

## perl / evalperl

The 'perl' filter evaluates the block as Perl code. The EVAL_PERL option must be set to a true value or a 'perl' exception will be thrown.

    [% my_perl_code | perl %]

In most cases, the [% PERL %] ... [% END %] block should suffice for evaluating Perl code, given that template directives are processed before being evaluate as Perl. Thus, the previous example could have been written in the more verbose form:

    [% PERL %]
[% my_perl_code %]
[% END %]

as well as

    [% FILTER perl %]
[% my_perl_code %]
[% END %]

The 'evalperl' filter is provided as an alias for 'perl' for backwards compatibility.

## stdout(options)

The stdout filter prints the output generated by the enclosing block to STDOUT. The 'binmode' option can be passed as either a named parameter or a single argument to set STDOUT to binary mode (see the binmode perl function).

    [% PROCESS something/cool
FILTER stdout(binmode=1) # recommended %]

[% PROCESS something/cool
FILTER stdout(1)         # alternate %]

The stdout filter can be used to force binmode on STDOUT, or also inside redirect, null or stderr blocks to make sure that particular output goes to stdout. See the null filter below for an example.

## stderr

The stderr filter prints the output generated by the enclosing block to STDERR.

## null

The null filter prints nothing. This is useful for plugins whose methods return values that you don't want to appear in the output. Rather than assigning every plugin method call to a dummy variable to silence it, you can wrap the block in a null filter:

    [% FILTER null;
USE im = GD.Image(100,100);
black = im.colorAllocate(0,   0, 0);
red   = im.colorAllocate(255,0,  0);
blue  = im.colorAllocate(0,  0,  255);
im.arc(50,50,95,75,0,360,blue);
im.fill(50,50,red);
im.png | stdout(1);
END;
-%]

Notice the use of the stdout filter to ensure that a particular expression generates output to stdout (in this case in binary mode).

## latex(outputType)

Passes the text block to LaTeX and produces either PDF, DVI or PostScript output. The 'outputType' argument determines the output format and it should be set to one of the strings: "pdf" (default), "dvi", or "ps".

The text block should be a complete LaTeX source file.

    [% FILTER latex("pdf") -%]
\documentclass{article}

\begin{document}

\title{A Sample TT2 \LaTeX\ Source File}
\author{Craig Barratt}
\maketitle

\section{Introduction}
This is some text.

\end{document}
[% END -%]

The output will be a PDF file. You should be careful not to prepend or append any extraneous characters or text outside the FILTER block, since this text will wrap the (binary) output of the latex filter. Notice the END directive uses '-%]' for the END_TAG to remove the trailing new line.

One example where you might prepend text is in a CGI script where you might include the Content-Type before the latex output, eg:

    Content-Type: application/pdf

[% FILTER latex("pdf") -%]
\documentclass{article}
\begin{document}
...
\end{document}
[% END -%]

In other cases you might use the redirect filter to put the output into a file, rather than delivering it to stdout. This might be suitable for batch scripts:

    [% output = FILTER latex("pdf") -%]
\documentclass{article}
\begin{document}
...
\end{document}
[% END; output | redirect("document.pdf", 1) -%]

(Notice the second argument to redirect to force binary mode.)

Note that the latex filter runs one or two external programs, so it isn't very fast. But for modest documents the performance is adequate, even for interactive applications.

A error of type 'latex' will be thrown if there is an error reported by latex, pdflatex or dvips.

# AUTHOR

Andy Wardley <abw@andywardley.com>

http://www.andywardley.com/

# VERSION

Template Toolkit version 2.14, released on 04 October 2004.

  Copyright (C) 1996-2004 Andy Wardley.  All Rights Reserved.
Copyright (C) 1998-2002 Canon Research Centre Europe Ltd.