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|
= Preprocessor Extension Example
:navtitle: Preprocessor
Purpose::
Skim off front matter from the top of the document that gets used by site generators like Jekyll and Awestruct.
== sample-with-front-matter.adoc
[source,asciidoc]
----
tags: [announcement, website]
---
= Document Title
content
[subs=+attributes]
.Captured front matter
....
---
{front-matter}
---
....
----
== FrontMatterPreprocessor
[source,ruby]
----
require 'asciidoctor'
require 'asciidoctor/extensions'
class FrontMatterPreprocessor < Asciidoctor::Extensions::Preprocessor
def process document, reader
lines = reader.lines # get raw lines
return reader if lines.empty?
front_matter = []
if lines.first.chomp == '---'
original_lines = lines.dup
lines.shift
while !lines.empty? && lines.first.chomp != '---'
front_matter << lines.shift
end
if (first = lines.first).nil? || first.chomp != '---'
lines = original_lines
else
lines.shift
document.attributes['front-matter'] = front_matter.join.chomp
# advance the reader by the number of lines taken
(front_matter.length + 2).times { reader.advance }
end
end
reader
end
end
----
== Usage
[source,ruby]
----
Asciidoctor::Extensions.register do
preprocessor FrontMatterPreprocessor
end
Asciidoctor.convert_file 'sample-with-front-matter.adoc', safe: :safe
----
|
