Load and Convert Strings Using the API

This page explains how to load and convert AsciiDoc-formatted strings using the API. A string is the bare AsciiDoc content (often the contents of a file).

Load an AsciiDoc string

To parse an AsciiDoc-formatted string into a document object model, use:

doc = Asciidoctor.load '*This* is Asciidoctor.'

You can also read AsciiDoc from a file and pass it to the load method:

asciidoc = File.read 'document.adoc', mode: 'r:utf-8'
doc = Asciidoctor.load asciidoc, safe: :safe

Once you have loaded the document, you can convert it by calling the convert method:

doc.convert

However, if you’re only interested in converting the AsciiDoc source when using the API, then it’s better to use a convert entrypoint.

Convert an AsciiDoc string

To convert the AsciiDoc-formatted string directly to HTML, use:

puts Asciidoctor.convert '*This* is Asciidoctor.'

Here’s the output you will see:

<div class="paragraph">
<p><strong>This</strong> is Asciidoctor.</p>
</div>

You can also read AsciiDoc from a file and pass it to the convert method:

asciidoc = File.read 'document.adoc', mode: 'r:utf-8'
html = Asciidoctor.convert asciidoc, safe: :safe

When converting a string, Asciidoctor does not output a standalone document by default. Instead, it generates embedded output. Let’s learn why that is and how to control it.

Embedded output

When you pass an AsciiDoc string to Asciidoctor.convert to convert it to a backend format, such as HTML, the :standalone option is false by default. That means this method only returns the converted content. This content does not include the frame around that content (i.e., the header and footer) that’s included in a standalone document. In other words, it makes an embedded document. This default was chosen to make Asciidoctor consistent with other lightweight markup processors like Markdown.

Here’s what’s included in an embedded document:

  • The document title, but only if the showtitle attribute is set (no attribution and revision information)

  • The table of contents if the toc attribute is enabled (and not macro or preamble)

  • The converted document body

  • The footnotes unless the nofootnotes attribute is set

The embedded document is intended to be included in a template, such as one provided by a static site generator. That template is responsible for providing the styles and library integrations needed for the content to render properly.

Standalone output

You can still generate a standalone document when converting a string. To convert from an AsciiDoc string to a standalone output document, you need to explicitly set the :standalone option to true.

puts Asciidoctor.convert '*This* is Asciidoctor.', standalone: true

Now you’ll get a complete HTML file. The standalone output provides the framing around the content, which includes the styling and all the library integrations the content needs to properly render (e.g., the default stylesheet, MathJax, etc.). If you don’t set the :standalone option to true, you only get the embedded document (i.e., body content).

When the input or output is a file, the :standalone option is enabled by default. Thus, to instruct Asciidoctor to write standalone HTML to a file from an AsciiDoc string, the :to_file option is mandatory.

Asciidoctor.convert '*This* is Asciidoctor.', to_file: 'out.html'

If you want to generate embedded output when starting with a file, set the :standalone option to false. However, most of the time you’ll want to generate a standalone document when converting a file (which is why it’s default).

When converting a string, the TOC is only included by default when using the :standalone option as shown above (whether it’s enabled implicitly or explicitly). However, you can force it to be included without the header and footer by setting the toc attribute with a value of macro and using the toc::[] macro in the string itself.

Convert inline markup only

If you only want the inline markup to be returned, set the :doctype option to 'inline':

puts Asciidoctor.convert '*This* is Asciidoctor.', doctype: 'inline'

In this mode, Asciidoctor will only process the first block (e.g., paragraph) in the document and ignore the rest.

Convert to DocBook

You can produce DocBook 5.0 by setting the :backend option to 'docbook'. Since embedded DocBook isn’t that useful, we also enable the standalone document (i.e., header and footer) by setting the :standalone option to true.

puts Asciidoctor.convert '*This* is Asciidoctor.', standalone: true, backend: 'docbook'