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📋 NAME

Template::Manual::Filters - Standard filters

🚀 Quick Reference

Use Case	Command	Description
Format text with printf-like pattern	[% FILTER format('') %]	Apply a format string to each line
Convert to uppercase	[% "hello" FILTER upper %]	Fold input to UPPER CASE
Convert to lowercase	[% "Hello" FILTER lower %]	Fold input to lower case
Uppercase first character	[% "hello" FILTER ucfirst %]	First character to UPPER CASE
Lowercase first character	[% "HELLO" FILTER lcfirst %]	First character to lower case
Trim whitespace	[% INCLUDE myfile | trim %]	Remove leading/trailing whitespace
Collapse whitespace	[% FILTER collapse %]	Reduce multiple whitespace to single space, trim
Escape HTML	[% FILTER html %]	Convert , &, " to HTML entities
Full HTML entity encoding	[% FILTER html_entity %]	Encode all extended characters
Escape XML	[% FILTER xml %]	Same as html but also escapes '
Format paragraphs	[% FILTER html_para %]	Wrap double-newline blocks in <p> tags
Paragraph breaks with <br>	[% FILTER html_break %]	Join paragraphs with <br><br>
Preserve line breaks	[% FILTER html_line_break %]	Replace newlines with <br>
URI encode	[% 'my file.html' | uri %]	Encode reserved characters (RFC 3986)
URL encode (less aggressive)	[% page_url | url %]	Encode unsafe characters, not reserved
Indent text	[% FILTER indent('ME> ') %]	Indent with string or width (default 4)
Truncate text	[% FILTER truncate(21) %]	Truncate to length, append "..."
Repeat text	[% FILTER repeat(3) %]	Repeat block n times
Remove string/regex	[% FILTER remove('\s+') %]	Remove all occurrences of pattern
Replace string/regex	[% FILTER replace('\s+', '_') %]	Replace pattern with replacement
Redirect output to file	[% FILTER redirect("file.html") %]	Send block output to a file
Evaluate template directives	[% fragment | eval %]	Process block as template text
Evaluate Perl code	[% my_perl_code | perl %]	Run block as Perl (requires EVAL_PERL)
Print to STDOUT	[% FILTER stdout %]	Force output to STDOUT (with binmode option)
Print to STDERR	[% FILTER stderr %]	Send output to STDERR
Suppress output	[% FILTER null %]	Discard block output

🔤 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 <, >, &, and " 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 "<=>" 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 é). If neither module is available on your system then an html_entity exception will be thrown reporting an appropriate message.

If you want to force TT to use one of the above modules in preference to the other, then call either of the Template::Filters class methods: use_html_entities() or use_apache_util().

use Template::Filters;
Template::Filters->use_html_entities;

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

💠 xml

Same as the html filter, but adds ' which is the fifth XML built-in entity.

📄 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.

Mary had a little lamb.
[% END %]

Output:

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

<p>
Mary had a little lamb.
</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.

Mary had a little lamb.
[% 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.
Mary had a little lamb.
[% 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 3986) into a %nn hex escape.

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

Output:

my%20file.html

The uri filter correctly encodes all reserved characters, including &, @, /, ;, :, =, +, ? and $. This filter is typically used to encode parameters in a URL that could otherwise be interpreted as part of the URL. Here's an example:

[% path  = 'http://tt2.org/example'
   back  = '/other?foo=bar&baz=bam'
   title = 'Earth: "Mostly Harmless"'
%]
<a href="[% path %]?back=[% back | uri %]&title=[% title | uri %]">

The output generated is rather long so we'll show it split across two lines:

<a href="http://tt2.org/example?back=%2Fother%3Ffoo%3Dbar%26
baz%3Dbam&title=Earth%3A%20%22Mostly%20Harmless%22">

Without the uri filter the output would look like this (also split across two lines).

<a href="http://tt2.org/example?back=/other?foo=bar
&baz=bam&title=Earth: "Mostly Harmless"">

In this rather contrived example we've manage to generate both a broken URL (the repeated ? is not allowed) and a broken HTML element (the href attribute is terminated by the first " after Earth: leaving Mostly Harmless" dangling on the end of the tag in precisely the way that harmless things shouldn't dangle). So don't do that. Always use the uri filter to encode your URL parameters.

However, you should not use the uri filter to encode an entire URL.

<a href="[% page_url | uri %]">   # WRONG!

This will incorrectly encode any reserved characters like : and / and that's almost certainly not what you want in this case. Instead you should use the url (note spelling) filter for this purpose.

<a href="[% page_url | url %]">   # CORRECT

Please note that this behaviour was changed in version 2.16 of the Template Toolkit. Prior to that, the uri filter did not encode the reserved characters, making it technically incorrect according to the RFC 2396 specification (since superceded by RFC2732 and RFC3986). So we fixed it in 2.16 and provided the url filter to implement the old behaviour of not encoding reserved characters.

As of version 2.26 of the Template Toolkit, the uri and url filters use the unsafe character set defined by RFC3986. This means that certain characters ((, ), ~, *, ! and the single quote ') are now deemed unsafe and will be escaped as hex character sequences. The double quote character (") is now deemed safe and will not be escaped.

If you want to enable the old behaviour then call the use_rfc2732() method in Template::Filters

use Template::Filters
Template::Filters->use_rfc2732;

🔗 url

The url filter is a less aggressive version of the uri filter. It encodes any characters outside of the permitted URI character set (as defined by RFC 2396) into %nn hex escapes. However, unlike the uri filter, the url filter does not encode the reserved characters &, @, /, ;, :, =, +, ? and $.

↔️ indent(pad)

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,dots)

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...

If you want to use something other than ... you can pass that as a second argument.

[% FILTER truncate(26, '…') %]
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 IN myorg.userlist %]
   [% FILTER redirect("users/${user.id}.html") %]
      [% INCLUDE userinfo %]
   [% END %]
[% END %]

or more succinctly, using side-effect notation:

[%  FOREACH user IN myorg.userlist;
      INCLUDE userinfo
        FILTER redirect("users/${user.id}.html");
    END
%]

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).

📋 NAME 🚀 Quick Reference