# Earmark—A Pure Elixir Markdown Processor
[](https://travis-ci.org/pragdave/earmark)
[](https://hex.pm/packages/earmark)
[](https://hex.pm/packages/earmark)
[](https://hex.pm/packages/earmark)
## Table Of Contents
<!-- BEGIN generated TOC -->
* [Dependency](#dependency)
* [Usage](#usage)
* [Details](#details)
* [Plugins](#plugins)
* [Contributing](#contributing)
* [Author](#author)
<!-- END generated TOC -->
## Dependency
{ :earmark, "> x.y.z" }
## Usage
<!-- BEGIN inserted moduledoc Earmark -->
### API
#### Earmark.as_html
{:ok, html_doc, []} = Earmark.as_html(markdown)
{:ok, html_doc, deprecation_messages} = Earmark.as_html(markdown)
{:error, html_doc, error_messages} = Earmark.as_html(markdown)
#### Earmark.as_html!
html_doc = Earmark.as_html!(markdown, options)
All messages are printed to _stderr_.
#### Options:
Options can be passed into `as_html` or `as_html!` according to the [documentation](#as_html/2).
html_doc = Earmark.as_html!(markdown)
html_doc = Earmark.as_html!(markdown, options)
Formats the error_messages returned by `as_html` and adds the filename to each.
Then prints them to stderr and just returns the html_doc
### Command line
$ mix escript.build
$ ./earmark file.md
Some options defined in the `Earmark.Options` struct can be specified as command line switches.
Use
$ ./earmark --help
to find out more, but here is a short example
$ ./earmark --smartypants false --code-class-prefix "a- b-" file.md
will call
Earmark.as_html!( ..., %Earmark.Options{smartypants: false, code_class_prefix: "a- b-"})
## Supports
Standard [Gruber markdown][gruber].
[gruber]: <http://daringfireball.net/projects/markdown/syntax>
## Extensions
### Github Flavored Markdown
GFM is supported by default, however as GFM is a moving target and all GFM extension do not make sense in a general context, Earmark does not support all of it, here is a list of what is supported:
* Strike Through
iex(1)> Earmark.as_html! ["~~hello~~"]
"<p><del>hello</del></p>\n"
* Syntax Highlighting
The generated code blocks have a corresponding `class` attribute:
iex(2)> Earmark.as_html! ["```elixir", " [] |> Enum.into(%{})", "```"]
"<pre><code class=\"elixir\"> [] |> Enum.into(%{})</code></pre>\n"
which can be customized with the `code_class_prefix` option
iex(3)> Earmark.as_html! ["```elixir", " [] |> Enum.into(%{})", "```"] , %Earmark.Options{code_class_prefix: "lang-"}
"<pre><code class=\"elixir lang-elixir\"> [] |> Enum.into(%{})</code></pre>\n"
* Tables
Are supported as long as they are preceded by an empty line.
State | Abbrev | Capital
----: | :----: | -------
Texas | TX | Austin
Maine | ME | Augusta
Tables may have leading and trailing vertical bars on each line
| State | Abbrev | Capital |
| ----: | :----: | ------- |
| Texas | TX | Austin |
| Maine | ME | Augusta |
Tables need not have headers, in which case all column alignments
default to left.
| Texas | TX | Austin |
| Maine | ME | Augusta |
Currently we assume there are always spaces around interior vertical
bars. It isn't clear what the expectation is.
### Adding HTML attributes with the IAL extension
#### To block elements
HTML attributes can be added to any block-level element. We use
the Kramdown syntax: add the line `{:` _attrs_ `}` following the block.
_attrs_ can be one or more of:
* `.className`
* `#id`
* name=value, name="value", or name='value'
For example:
# Warning
{: .red}
Do not turn off the engine
if you are at altitude.
{: .boxed #warning spellcheck="true"}
#### To links or images
It is possible to add IAL attributes to generated links or images in the following
format.
iex(4)> markdown = "[link](url) {: .classy}"
...(4)> Earmark.as_html(markdown)
{ :ok, "<p><a href=\"url\" class=\"classy\">link</a></p>\n", []}
For both cases, malformed attributes are ignored and warnings are issued.
iex(5)> [ "Some text", "{:hello}" ] |> Enum.join("\n") |> Earmark.as_html()
{:error, "<p>Some text</p>\n", [{:warning, 2,"Illegal attributes [\"hello\"] ignored in IAL"}]}
It is possible to escape the IAL in both forms if necessary
iex(6)> markdown = "[link](url)\\{: .classy}"
...(6)> Earmark.as_html(markdown)
{:ok, "<p><a href=\"url\">link</a>{: .classy}</p>\n", []}
This of course is not necessary in code blocks or text lines
containing an IAL-like string, as in the following example
iex(7)> markdown = "hello {:world}"
...(7)> Earmark.as_html!(markdown)
"<p>hello {:world}</p>\n"
## Limitations
* Block-level HTML is correctly handled only if each HTML
tag appears on its own line. So
<div>
<div>
hello
</div>
</div>
will work. However. the following won't
<div>
hello</div>
* John Gruber's tests contain an ambiguity when it comes to
lines that might be the start of a list inside paragraphs.
One test says that
This is the text
* of a paragraph
that I wrote
is a single paragraph. The "*" is not significant. However, another
test has
* A list item
* an another
and expects this to be a nested list. But, in reality, the second could just
be the continuation of a paragraph.
I've chosen always to use the second interpretation—a line that looks like
a list item will always be a list item.
* Rendering of block and inline elements.
Block or void HTML elements that are at the absolute beginning of a line end
the preceding paragraph.
Thusly
mypara
<hr>
Becomes
<p>mypara</p>
<hr>
While
mypara
<hr>
will be transformed into
<p>mypara
<hr></p>
## Integration
### Syntax Highlighting
All backquoted or fenced code blocks with a language string are rendered with the given
language as a _class_ attribute of the _code_ tag.
For example:
iex(8)> [
...(8)> "```elixir",
...(8)> " @tag :hello",
...(8)> "```"
...(8)> ] |> Earmark.as_html!()
"<pre><code class=\"elixir\"> @tag :hello</code></pre>\n"
will be rendered as shown in the doctest above.
If you want to integrate with a syntax highlighter with different conventions you can add more classes by specifying prefixes that will be
put before the language string.
Prism.js for example needs a class `language-elixir`. In order to achieve that goal you can add `language-`
as a `code_class_prefix` to `Earmark.Options`.
In the following example we want more than one additional class, so we add more prefixes.
Earmark.as_html!(..., %Earmark.Options{code_class_prefix: "lang- language-"})
which is rendering
<pre><code class="elixir lang-elixir language-elixir">...
As for all other options `code_class_prefix` can be passed into the `earmark` executable as follows:
earmark --code-class-prefix "language- lang-" ...
## Timeouts
By default, that is if the `timeout` option is not set Earmark uses parallel mapping as implemented in `Earmark.pmap/2`,
which uses `Task.await` with its default timeout of 5000ms.
In rare cases that might not be enough.
By indicating a longer `timeout` option in milliseconds Earmark will use parallel mapping as implemented in `Earmark.pmap/3`,
which will pass `timeout` to `Task.await`.
In both cases one can override the mapper function with either the `mapper` option (used if and only if `timeout` is nil) or the
`mapper_with_timeout` function (used otherwise).
For the escript only the `timeout` command line argument can be used.
## Security
Please be aware that Markdown is not a secure format. It produces
HTML from Markdown and HTML. It is your job to sanitize and or
filter the output of `Earmark.as_html` if you cannot trust the input
and are to serve the produced HTML on the Web.
<!-- END inserted moduledoc Earmark -->
## Details
<!-- BEGIN inserted functiondoc Earmark.as_html/2 -->
Given a markdown document (as either a list of lines or
a string containing newlines), returns a tuple containing either
`{:ok, html_doc, error_messages}`, or `{:error, html_doc, error_messages}`
Where `html_doc` is an HTML representation of the markdown document and
`error_messages` is a list of tuples with the following elements
- `severity` e.g. `:error`, `:warning` or `:deprecation`
- line number in input where the error occurred
- description of the error
`options` can be an `%Earmark.Options{}` structure, or can be passed in as a `Keyword` argument (with legal keys for `%Earmark.Options`
* `renderer`: ModuleName
The module used to render the final document. Defaults to
`Earmark.HtmlRenderer`
* `gfm`: boolean
True by default. Turns on the supported Github Flavored Markdown extensions
* `breaks`: boolean
Only applicable if `gfm` is enabled. Makes all line breaks
significant (so every line in the input is a new line in the
output.
* `code_class_prefix`: binary
Code blocks will be rendered with prefixed class names, which might be necessary for
usage with 3rd party libraries.
Earmark.as_html("```elixir\nCode\n```", code_class_prefix: "my_prefix_")
{:ok, "<pre><code class=\"elixir my_prefix_elixir\">Code\```</code></pre>\n", []}
* `smartypants`: boolean
Turns on smartypants processing, so quotes become curly, two
or four hyphens become en and em dashes, and so on. True by
default.
So, to format the document in `original` and disable smartypants,
you'd call
alias Earmark.Options
Earmark.as_html(original, %Options{smartypants: false})
* `pure_links`: boolean
Pure links of the form `~r{\bhttps?://\S+\b}` are not rendered as links in this version yet.
However, by setting the `pure_links` option to `true` one can enable this behavior.
There are three possible cases
- Default (option is set to `nil`), gives a deprecation warning
```elixir
Earmark.as_html("https://github.com/pragdave")
{:ok, "<p>https://github.com/pragdave</p>\n",
[
{:deprecation, 1,
"The string "https://github.com/pragdave/earmark" will be rendered as a link if the option `pure_links` is enabled.\nThis will be the case by default in version 1.4.\nDisable the option explicitly with `false` to avoid this message."}
]}
```
- `pure_links: true`
```elixir
Earmark.as_html("https://github.com/pragdave", pure_links: true)
{:ok,
"<p><a href="https://github.com/pragdave">https://github.com/pragdave</a></p>\n", []}
```
- Explicitly setting `pure_links` to `false` surpresses the deprecation warning
```elixir
Earmark.as_html("https://github.com/pragdave", pure_links: false)
{:ok, "<p>https://github.com/pragdave</p>\n", []}
```
<!-- END inserted functiondoc Earmark.as_html/2 -->
## Plugins
<!-- BEGIN inserted moduledoc Earmark.Plugin -->
DEPRECATED!!!
<!-- END inserted moduledoc Earmark.Plugin -->
## Contributing
Pull Requests are happily accepted.
Please be aware of one _caveat_ when correcting/improving `README.md`.
The `README.md` is generated by the mix task `readme` from `README.template` and
docstrings by means of `%moduledoc` or `%functiondoc` directives.
Please identify the origin of the generated text you want to correct and then
apply your changes there.
Then issue the mix task `readme`, this is important to have a correctly updated `README.md` after the merge of
your PR.
Thank you all who have already helped with Earmark, your names are duely noted in [CHANGELOG.md](CHANGELOG.md).
## Author
Copyright © 2014,5,6,7,8 Dave Thomas, The Pragmatic Programmers
@/+pragdave, dave@pragprog.com
# LICENSE
Same as Elixir, which is Apache License v2.0. Please refer to [LICENSE](LICENSE) for details.
SPDX-License-Identifier: Apache-2.0
