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Template::Manual::Syntax(3)    User Contributed Perl Documentation    Template::Manual::Syntax(3)

NAME
       Template::Manual::Syntax - Directive syntax, structure and semantics

Tag Styles
       By default, template directives are embedded within the character sequences "[%" and "%]".

	   [% PROCESS header %]

	   <h1>Hello World!</h1>
	   <a href="[% page.next %]"><img src="[% icon.next %].gif"></a>

	   [% PROCESS footer %]

       You can change the tag characters using the "START_TAG", "END_TAG" and "TAG_STYLE"
       configuration options. You can also use the "TAGS" directive to define a new tag style for
       the current template file.

       You can also set the "INTERPOLATE" option to allow simple variable references to be
       embedded directly in templates, prefixed by a "$".

	   # INTERPOLATE = 0
	   <td>[% name %]</td>
	   <td>[% email %]</td>

	   # INTERPOLATE = 1
	   <td>$name</td>
	   <td>$email</td>

       Directives may be embedded anywhere in a line of text and can be split across several
       lines.  Insignificant whitespace is generally ignored within the directive.

	   [% INCLUDE header
		title = 'Hello World'
		bgcol = '#ffffff'
	   %]

	   [%INCLUDE menu align='right'%]

	   Name: [% name %]  ([%id%])

Comments
       The "#" character is used to indicate comments within a directive.  When placed
       immediately inside the opening directive tag, it causes the entire directive to be
       ignored.

	   [%# this entire directive is ignored no
	       matter how many lines it wraps onto
	   %]

       In any other position, it causes the remainder of the current line to be treated as a
       comment.

	   [% # this is a comment
	      theta = 20      # so is this
	      rho   = 30      # <aol>me too!</aol>
	   %]

Chomping Whitespace
       You can add "-" or "+" to the immediate start or end of a directive tag to control the
       whitespace chomping options.  See the "PRE_CHOMP" and "POST_CHOMP" options for further
       details.

	   [% BLOCK foo -%]    # remove trailing newline
	   This is block foo
	   [%- END %]	       # remove leading newline

Implicit Directives: GET and SET
       The simplest directives are "GET" and "SET" which retrieve and update variable values
       respectively. The "GET" and "SET" keywords are actually optional as the parser is smart
       enough to see them for what they really are (but note the caveat below on using side-
       effect notation). Thus, you'll generally see:

	   [% SET foo = 10 %]
	   [% GET foo %]

       written as:

	   [% foo = 10 %]
	   [% foo %]

       You can also express simple logical statements as implicit "GET" directives:

	   [% title or template.title or 'Default Title' %]

	   [% mode == 'graphics' ? "Graphics Mode Enabled" : "Text Mode" %]

       All other directives should start with a keyword specified in UPPER CASE (but see the
       "ANYCASE" option).  All directives keywords are in UPPER CASE to make them visually
       distinctive and to distinguish them from variables of the same name but different case.
       It is perfectly valid, for example, to define a variable called "stop" which is entirely
       separate from the "STOP" directive.

	   [% stop = 'Clackett Lane Bus Depot' %]

	   The bus will next stop at [% stop %]    # variable

	   [% STOP %]				   # directive

Block Directives
       Directives such as "FOREACH", "WHILE", "BLOCK", "FILTER", etc., mark the start of a block
       which may contain text or other directives up to the matching "END" directive. Blocks may
       be nested indefinitely. The "IF", "UNLESS", "ELSIF" and "ELSE" directives also define
       blocks and may be grouped together in the usual manner.

	   [% FOREACH item = [ 'foo' 'bar' 'baz' ] %]
	      * Item: [% item %]
	   [% END %]

	   [% BLOCK footer %]
	      Copyright 2000 [% me %]
	      [% INCLUDE company/logo %]
	   [% END %]

	   [% IF foo %]
	      [% FOREACH thing = foo.things %]
		 [% thing %]
	      [% END %]
	   [% ELSIF bar %]
	      [% INCLUDE barinfo %]
	   [% ELSE %]
	      do nothing...
	   [% END %]

       Block directives can also be used in a convenient side-effect notation.

	   [% INCLUDE userinfo FOREACH user = userlist %]

	   [% INCLUDE debugtxt msg="file: $error.info"
		IF debugging %]

	   [% "Danger Will Robinson" IF atrisk %]

       versus:

	   [% FOREACH user = userlist %]
	      [% INCLUDE userinfo %]
	   [% END %]

	   [% IF debugging %]
	      [% INCLUDE debugtxt msg="file: $error.info" %]
	   [% END %]

	   [% IF atrisk %]
	   Danger Will Robinson
	   [% END %]

Capturing Block Output
       The output of a directive can be captured by simply assigning the directive to a variable.

	   [% headtext = PROCESS header title="Hello World" %]

	   [% people = PROCESS userinfo FOREACH user = userlist %]

       This can be used in conjunction with the "BLOCK" directive for defining large blocks of
       text or other content.

	   [% poem = BLOCK %]
	      The boy stood on the burning deck,
	      His fleece was white as snow.
	      A rolling stone gathers no moss,
	      And Keith is sure to follow.
	   [% END %]

       Note one important caveat of using this syntax in conjunction with side-effect notation.
       The following directive does not behave as might be expected:

	   [% var = 'value' IF some_condition %]   # does not work

       In this case, the directive is interpreted as (spacing added for clarity)

	   [% var = IF some_condition %]
	      value
	   [% END %]

       rather than

	   [% IF some_condition %]
	      [% var = 'value' %]
	   [% END %]

       The variable is assigned the output of the "IF" block which returns 'value' if true, but
       nothing if false.  In other words, the following directive will always cause 'var' to be
       cleared.

	   [% var = 'value' IF 0 %]

       To achieve the expected behaviour, the directive should be written as:

	   [% SET var = 'value' IF some_condition %]

Chaining Filters
       Multiple "FILTER" directives can be chained together in sequence.  They are called in the
       order defined, piping the output of one into the input of the next.

	   [% PROCESS somefile FILTER truncate(100) FILTER html %]

       The pipe character, "|", can also be used as an alias for "FILTER".

	   [% PROCESS somefile | truncate(100) | html %]

Multiple Directive Blocks
       Multiple directives can be included within a single tag when delimited by semi-colons.
       Note however that the "TAGS" directive must always be specified in a tag by itself.

	   [% IF title;
		 INCLUDE header;
	      ELSE;
		 INCLUDE other/header  title="Some Other Title";
	      END
	   %]

       versus

	   [% IF title %]
	      [% INCLUDE header %]
	   [% ELSE %]
	      [% INCLUDE other/header  title="Some Other Title" %]
	   [% END %]

perl v5.16.3				    2011-12-20		      Template::Manual::Syntax(3)
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