markdown (7) - Linux Manuals
markdown: The Markdown text formatting syntax
NAME
Markdown - The Markdown text formatting syntax
DESCRIPTION
Philosophy
Markdown is intended to be as easy-to-read and easy-to-write as is feasible.Readability, however, is emphasized above all else. A Markdown-formatted document should be publishable as-is, as plain text, without looking like it's been marked up with tags or formatting instructions. While Markdown's syntax has been influenced by several existing text-to-HTML filters -- including Setext atx Textile reStructuredText Grutatext and EtText -- the single biggest source of inspiration for Markdown's syntax is the format of plain text email.
To this end, Markdown's syntax is comprised entirely of punctuation characters, which punctuation characters have been carefully chosen so as to look like what they mean. E.g., asterisks around a word actually look like *emphasis*. Markdown lists look like, well, lists. Even blockquotes look like quoted passages of text, assuming you've ever used email.
Inline HTML
Markdown's syntax is intended for one purpose: to be used as a format for writing for the web.is not a replacement for HTML, or even close to it. Its syntax is very small, corresponding only to a very small subset of HTML tags. The idea is not to create a syntax that makes it easier to insert HTML tags. In my opinion, HTML tags are already easy to insert. The idea for Markdown is to make it easy to read, write, and edit prose. HTML is a publishing format; Markdown is a writing format. Thus, Markdown's formatting syntax only addresses issues that can be conveyed in plain text.
For any markup that is not covered by Markdown's syntax, you simply use HTML itself. There's no need to preface it or delimit it to indicate that you're switching from Markdown to HTML; you just use the tags.
The only restrictions are that block-level HTML elements -- e.g. <div> <table> <pre> <p> etc. -- must be separated from surrounding content by blank lines, and the start and end tags of the block should not be indented with tabs or spaces. Markdown is smart enough not to add extra (unwanted) <p> tags around HTML block-level tags.
For example, to add an HTML table to a Markdown article:
This is a regular paragraph.
<table>
<tr>
<td>Foo</td>
</tr>
</table>
This is another regular paragraph.
Note that Markdown formatting syntax is not processed within block-level HTML tags. E.g., you can't use Markdown-style *emphasis* inside an HTML block.
Span-level HTML tags -- e.g. <span> <cite> or <del> -- can be used anywhere in a Markdown paragraph, list item, or header. If you want, you can even use HTML tags instead of Markdown formatting; e.g. if you'd prefer to use HTML <a> or <img> tags instead of Markdown's link or image syntax, go right ahead.
Unlike block-level HTML tags, Markdown syntax *is* processed within span-level tags.
Automatic Escaping for Special Characters
In HTML, there are two characters that demand special treatment: `<` and `&`. Left angle brackets are used to start tags; ampersands are used to denote HTML entities. If you want to use them as literal characters, you must escape them as entities, e.g. `<`, and `&`.Ampersands in particular are bedeviling for web writers. If you want to write about 'AT&T', you need to write '`AT&T`'. You even need to escape ampersands within URLs. Thus, if you want to link to:
http://images.google.com/images?num=30&q=larry+bird
you need to encode the URL as:
http://images.google.com/images?num=30&q=larry+bird
in your anchor tag `href` attribute. Needless to say, this is easy to forget, and is probably the single most common source of HTML validation errors in otherwise well-marked-up web sites.
allows you to use these characters naturally, taking care of all the necessary escaping for you. If you use an ampersand as part of an HTML entity, it remains unchanged; otherwise it will be translated into `&`.
So, if you want to include a copyright symbol in your article, you can write:
©
and Markdown will leave it alone. But if you write:
AT&T
will translate it to:
AT&T
Similarly, because Markdown supports inline HTML, if you use angle brackets as delimiters for HTML tags, Markdown will treat them as such. But if you write:
4 < 5
will translate it to:
4 < 5
However, inside Markdown code spans and blocks, angle brackets and ampersands are *always* encoded automatically. This makes it easy to use Markdown to write about HTML code. (As opposed to raw HTML, which is a terrible format for writing about HTML syntax, because every single `<` and `&` in your example code needs to be escaped.)
Block Elements
Paragraphs and Line Breaks
A paragraph is simply one or more consecutive lines of text, separated by one or more blank lines. (A blank line is any line that looks like a blank line -- a line containing nothing but spaces or tabs is considered blank.) Normal paragraphs should not be indented with spaces or tabs.
The implication of the Qq one or more consecutive lines of text rule is that Markdown supports Qq hard-wrapped Dtext paragraphs. This differs significantly from most other text-to-HTML formatters (including Movable Type's Qq Convert Line Breaks option) which translate every line break character in a paragraph into a `<br />` tag.
When you *do* want to insert a `<br />` break tag using Markdown, you end a line with two or more spaces, then type return.
Yes, this takes a tad more effort to create a `<br />`, but a simplistic
"every line break is a `<br />`" rule wouldn't work for Markdown.
Markdown's email-style
Sx blockquoting
Setext-style headers are
`underlined'
using equal signs (for first-level
headers) and dashes (for second-level headers). For example:
Any number of underlining `=`'s or `-`'s will work.
Atx-style headers use 1-6 hash characters at the start of the line,
corresponding to header levels 1-6. For example:
Optionally, you may
Qq close
atx-style headers. This is purely
cosmetic -- you can use this if you think it looks better. The
closing hashes don't even need to match the number of hashes
used to open the header. (The number of opening hashes
determines the header level.) :
allows you to be lazy and only put the `>` before the first
line of a hard-wrapped paragraph:
Blockquotes can be nested (i.e. a blockquote-in-a-blockquote) by
adding additional levels of `>`:
Blockquotes can contain other Markdown elements, including headers, lists,
and code blocks:
Any decent text editor should make email-style quoting easy. For
example, with BBEdit, you can make a selection and choose Increase
Quote Level from the Text menu.
Unordered lists use asterisks, pluses, and hyphens -- interchangably
-- as list markers:
is equivalent to:
and:
Ordered lists use numbers followed by periods:
It's important to note that the actual numbers you use to mark the
list have no effect on the HTML output Markdown produces. The HTML
Markdown produces from the above list is:
If you instead wrote the list in Markdown like this:
or even:
you'd get the exact same HTML output. The point is, if you want to,
you can use ordinal numbers in your ordered Markdown lists, so that
the numbers in your source match the numbers in your published HTML.
But if you want to be lazy, you don't have to.
If you do use lazy list numbering, however, you should still start the
list with the number 1. At some point in the future, Markdown may support
starting ordered lists at an arbitrary number.
List markers typically start at the left margin, but may be indented by
up to three spaces. List markers must be followed by one or more spaces
or a tab.
To make lists look nice, you can wrap items with hanging indents:
But if you want to be lazy, you don't have to:
If list items are separated by blank lines, Markdown will wrap the
items in `<p>` tags in the HTML output. For example, this input:
will turn into:
But this:
will turn into:
List items may consist of multiple paragraphs. Each subsequent
paragraph in a list item must be intended by either 4 spaces
or one tab:
It looks nice if you indent every line of the subsequent
paragraphs, but here again, Markdown will allow you to be
lazy:
To put a blockquote within a list item, the blockquote's `>`
delimiters need to be indented:
To put a code block within a list item, the code block needs
to be indented *twice* -- 8 spaces or two tabs:
It's worth noting that it's possible to trigger an ordered list by
accident, by writing something like this:
In other words, a *number-period-space* sequence at the beginning of a
line. To avoid this, you can backslash-escape the period:
To produce a code block in Markdown, simply indent every line of the
block by at least 4 spaces or 1 tab. For example, given this input:
will generate:
One level of indentation -- 4 spaces or 1 tab -- is removed from each
line of the code block. For example, this:
will turn into:
A code block continues until it reaches a line that is not indented
(or the end of the article).
Within a code block, ampersands (`&`) and angle brackets (`<` and `>`)
are automatically converted into HTML entities. This makes it very
easy to include example HTML source code using Markdown -- just paste
it and indent it, and Markdown will handle the hassle of encoding the
ampersands and angle brackets. For example, this:
will turn into:
Regular Markdown syntax is not processed within code blocks. E.g.,
asterisks are just literal asterisks within a code block. This means
it's also easy to use Markdown to write about Markdown's own syntax.
In both styles, the link text is delimited by [square brackets].
To create an inline link, use a set of regular parentheses immediately
after the link text's closing square bracket. Inside the parentheses,
put the URL where you want the link to point, along with an *optional*
title for the link, surrounded in quotes. For example:
Will produce:
If you're referring to a local resource on the same server, you can
use relative paths:
Reference-style links use a second set of square brackets, inside
which you place a label of your choosing to identify the link:
You can optionally use a space to separate the sets of brackets:
Then, anywhere in the document, you define your link label like this,
on a line by itself:
That is:
The following three link definitions are equivalent:
Note
There is a known bug in Markdown.pl 1.0.1 which prevents
single quotes from being used to delimit link titles.
The link URL may, optionally, be surrounded by angle brackets:
You can put the title attribute on the next line and use extra spaces
or tabs for padding, which tends to look better with longer URLs:
Link definitions are only used for creating links during Markdown
processing, and are stripped from your document in the HTML output.
Link definition names may constist of letters, numbers, spaces, and
punctuation -- but they are
not
case sensitive. E.g. these two
links:
are equivalent.
The
implicit link name
shortcut allows you to omit the name of the
link, in which case the link text itself is used as the name.
Just use an empty set of square brackets -- e.g., to link the word
Qq Google
to the google.com web site, you could simply write:
And then define the link:
Because link names may contain spaces, this shortcut even works for
multiple words in the link text:
And then define the link:
Link definitions can be placed anywhere in your Markdown document. I
tend to put them immediately after each paragraph in which they're
used, but if you want, you can put them all at the end of your
document, sort of like footnotes.
Here's an example of reference links in action:
Using the implicit link name shortcut, you could instead write:
Both of the above examples will produce the following HTML output:
For comparison, here is the same paragraph written using
Markdown's inline link style:
The point of reference-style links is not that they're easier to
write. The point is that with reference-style links, your document
source is vastly more readable. Compare the above examples: using
reference-style links, the paragraph itself is only 81 characters
long; with inline-style links, it's 176 characters; and as raw HTML,
it's 234 characters. In the raw HTML, there's more markup than there
is text.
With Markdown's reference-style links, a source document much more
closely resembles the final output, as rendered in a browser. By
allowing you to move the markup-related metadata out of the paragraph,
you can add links without interrupting the narrative flow of your
prose.
will produce:
You can use whichever style you prefer; the lone restriction is that
the same character must be used to open and close an emphasis span.
Emphasis can be used in the middle of a word:
But if you surround an `*` or `_` with spaces, it'll be treated as a
literal asterisk or underscore.
To produce a literal asterisk or underscore at a position where it
would otherwise be used as an emphasis delimiter, you can backslash
escape it:
will produce:
To include a literal backtick character within a code span, you can use
multiple backticks as the opening and closing delimiters:
which will produce this:
The backtick delimiters surrounding a code span may include spaces --
one after the opening, one before the closing. This allows you to place
literal backtick characters at the beginning or end of a code span:
will produce:
With a code span, ampersands and angle brackets are encoded as HTML
entities automatically, which makes it easy to include example HTML
tags. Markdown will turn this:
into:
You can write this:
to produce:
Markdown uses an image syntax that is intended to resemble the syntax
for links, allowing for two styles:
inline
and
reference
Inline image syntax looks like this:
That is:
Reference-style image syntax looks like this:
Where
Qq id
is the name of a defined image reference. Image references
are defined using syntax identical to link references:
will turn this into:
Automatic links for email addresses work similarly, except that
Markdown will also perform a bit of randomized decimal and hex
entity-encoding to help obscure your address from address-harvesting
spambots. For example, Markdown will turn this:
into something like this:
which will render in a browser as a clickable link to
Qq address [at] example.com .
(This sort of entity-encoding trick will indeed fool many, if not
most, address-harvesting bots, but it definitely won't fool all of
them. It's better than nothing, but an address published in this way
will probably eventually start receiving spam.)
provides backslash escapes for the following characters:
http://daringfireball.net/projects/markdown
Headers
supports two styles of headers,
Setext
and
atx
This is an H1
=============
This is an H2
-------------
# This is an H1
## This is an H2
###### This is an H6
# This is an H1 #
## This is an H2 ##
### This is an H3 ######
Blockquotes
uses email-style `>` characters for blockquoting. If you're
familiar with quoting passages of text in an email message, then you
know how to create a blockquote in Markdown. It looks best if you hard
wrap the text and put a `>` before every line:
> This is a blockquote with two paragraphs. Lorem ipsum
> dolor sit amet, consectetuer adipiscing elit. Aliquam
> hendrerit mi posuere lectus. Vestibulum enim wisi,
> viverra nec, fringilla in, laoreet vitae, risus.
>
> Donec sit amet nisl. Aliquam semper ipsum sit amet
> velit. Suspendisse id sem consectetuer libero luctus
> adipiscing.
> This is a blockquote with two paragraphs. Lorem ipsum
dolor sit amet, consectetuer adipiscing elit. Aliquam
hendrerit mi posuere lectus. Vestibulum enim wisi,
viverra nec, fringilla in, laoreet vitae, risus.
> Donec sit amet nisl. Aliquam semper ipsum sit amet
velit. Suspendisse id sem consectetuer libero luctus
adipiscing.
> This is the first level of quoting.
>
> > This is nested blockquote.
>
> Back to the first level.
> ## This is a header.
>
> 1. This is the first list item.
> 2. This is the second list item.
>
> Here's some example code:
>
> return shell_exec("echo $input | $markdown_script");
Lists
supports ordered (numbered) and unordered (bulleted) lists.
* Red
* Green
* Blue
+ Red
+ Green
+ Blue
- Red
- Green
- Blue
1. Bird
2. McHale
3. Parish
<ol>
<li>Bird</li>
<li>McHale</li>
<li>Parish</li>
</ol>
1. Bird
1. McHale
1. Parish
3. Bird
1. McHale
8. Parish
* Lorem ipsum dolor sit amet, consectetuer adipiscing
elit. Aliquam hendrerit mi posuere lectus. Vestibulum
enim wisi, viverra nec, fringilla in, laoreet vitae,
risus.
* Donec sit amet nisl. Aliquam semper ipsum sit amet
velit. Suspendisse id sem consectetuer libero luctus
adipiscing.
* Lorem ipsum dolor sit amet, consectetuer adipiscing
elit. Aliquam hendrerit mi posuere lectus. Vestibulum
enim wisi, viverra nec, fringilla in, laoreet vitae,
risus.
* Donec sit amet nisl. Aliquam semper ipsum sit amet
velit. Suspendisse id sem consectetuer libero luctus
adipiscing.
* Bird
* Magic
<ul>
<li>Bird</li>
<li>Magic</li>
</ul>
* Bird
* Magic
<ul>
<li><p>Bird</p></li>
<li><p>Magic</p></li>
</ul>
1. This is a list item with two paragraphs. Lorem ipsum
dolor sit amet, consectetuer adipiscing elit. Aliquam
hendrerit mi posuere lectus.
Vestibulum enim wisi, viverra nec, fringilla in,
laoreet vitae, risus. Donec sit amet nisl. Aliquam
semper ipsum sit amet velit.
2. Suspendisse id sem consectetuer libero luctus
adipiscing.
* This is a list item with two paragraphs.
This is the second paragraph in the list item.
You're only required to indent the first line. Lorem
ipsum dolor sit amet, consectetuer adipiscing elit.
* Another item in the same list.
* A list item with a blockquote:
> This is a blockquote
> inside a list item.
* A list item with a code block:
<code goes here>
1986. What a great season.
1986\. What a great season.
Code Blocks
Pre-formatted code blocks are used for writing about programming or
markup source code. Rather than forming normal paragraphs, the lines
of a code block are interpreted literally. Markdown wraps a code block
in both `<pre>` and `<code>` tags.
This is a normal paragraph:
This is a code block.
<p>This is a normal paragraph:</p>
<pre><code>This is a code block.
</code></pre>
Here is an example of AppleScript:
tell application "Foo"
beep
end tell
<p>Here is an example of AppleScript:</p>
<pre><code>tell application "Foo"
beep
end tell
</code></pre>
<div class="footer">
© 2004 Foo Corporation
</div>
<pre><code><div class="footer">
&copy; 2004 Foo Corporation
</div>
</code></pre>
Horizontal Rules
You can produce a horizontal rule tag (`<hr />`) by placing three or
more hyphens, asterisks, or underscores on a line by themselves. If you
wish, you may use spaces between the hyphens or asterisks. Each of the
following lines will produce a horizontal rule:
* * *
***
*****
- - -
---------------------------------------
Span Elements
Links
supports two style of links:
inline
and
reference
This is [an example](http://example.com/ "Title") inline link.
[This link](http://example.net/) has no title attribute.
<p>This is <a href="http://example.com/" title="Title">
an example</a> inline link.</p>
<p><a href="http://example.net/">This link</a> has no
title attribute.</p>
See my [About](/about/) page for details.
This is [an example][id] reference-style link.
This is [an example] [id] reference-style link.
[id]: http://example.com/ "Optional Title Here"
[foo]: http://example.com/ "Optional Title Here"
[foo]: http://example.com/ 'Optional Title Here'
[foo]: http://example.com/ (Optional Title Here)
[id]: <http://example.com/> "Optional Title Here"
[id]: http://example.com/longish/path/to/resource/here
"Optional Title Here"
[link text][a]
[link text][A]
[Google][]
[Google]: http://google.com/
Visit [Daring Fireball][] for more information.
[Daring Fireball]: http://daringfireball.net/
I get 10 times more traffic from [Google] [1] than from
[Yahoo] [2] or [MSN] [3].
[1]: http://google.com/ "Google"
[2]: http://search.yahoo.com/ "Yahoo Search"
[3]: http://search.msn.com/ "MSN Search"
I get 10 times more traffic from [Google][] than from
[Yahoo][] or [MSN][].
[google]: http://google.com/ "Google"
[yahoo]: http://search.yahoo.com/ "Yahoo Search"
[msn]: http://search.msn.com/ "MSN Search"
<p>I get 10 times more traffic from <a href="http://google.com/"
title="Google">Google</a> than from
<a href="http://search.yahoo.com/" title="Yahoo Search">Yahoo</a>
or
<a href="http://search.msn.com/" title="MSN Search">MSN</a>.</p>
I get 10 times more traffic from
[Google](http://google.com/ "Google") than from
[Yahoo](http://search.yahoo.com/ "Yahoo Search") or
[MSN](http://search.msn.com/ "MSN Search").
Emphasis
Markdown treats asterisks (`*`) and underscores (`_`) as indicators of
emphasis. Text wrapped with one `*` or `_` will be wrapped with an
HTML `<em>` tag; double `*`'s or `_`'s will be wrapped with an HTML
`<strong>` tag. E.g., this input:
*single asterisks*
_single underscores_
**double asterisks**
__double underscores__
<em>single asterisks</em>
<em>single underscores</em>
<strong>double asterisks</strong>
<strong>double underscores</strong>
un*fucking*believable
\*this text is surrounded by literal asterisks\*
Code
To indicate a span of code, wrap it with backtick quotes (`` ` ``).
Unlike a pre-formatted code block, a code span indicates code within a
normal paragraph. For example:
Use the `printf()` function.
<p>Use the <code>printf()</code> function.</p>
``There is a literal backtick (`) here.``
<p><code>There is a literal backtick (`) here.</code></p>
A single backtick in a code span: `` ` ``
A backtick-delimited string in a code span: `` `foo` ``
<p>A single backtick in a code span: <code>`</code></p>
<p>A backtick-delimited string in a code span: <code>`foo`</code></p>
Please don't use any `<blink>` tags.
<p>Please don't use any <code><blink></code> tags.</p>
`—` is the decimal-encoded equivalent of `—`.
<p><code>&#8212;</code> is the decimal-encoded
equivalent of <code>&mdash;</code>.</p>
Images
Admittedly, it's fairly difficult to devise a
Qq natural
syntax for placing images into a plain text document format.
![Alt text][id]
[id]: url/to/image =Optional size "Optional title attribute"
Miscellaneous
Automatic Links
supports a shortcut style for creating
Qq automatic
links for URLs and email addresses: simply surround the URL or email
address with angle brackets. What this means is that if you want to
<http://example.com/>
<a href="http://example.com/">http://example.com/</a>
<address [at] example.com>
<a href="mailto:addre
ss@example.co
m">address@exa
mple.com</a>
Backslash Escapes
allows you to use backslash escapes to generate literal
characters which would otherwise have special meaning in Markdown's
formatting syntax. For example, if you wanted to surround a word with
literal asterisks (instead of an HTML `<em>` tag), you add backslashes
before the asterisks, like this:
\*literal asterisks\*
BUGS
assumes that tabs are set to 4 spaces.
AUTHOR
John Gruber
http://daringfireball.net/
SEE ALSO
markdown(1),
markdown(3),
mkd-callbacks3,
mkd-functions3,
mkd-extensions7.
http://docutils.sourceforge.net/mirror/setext.html
http://www.aaronsw.com/2002/atx/
http://textism.com/tools/textile/
http://docutils.sourceforge.net/rst.html
http://www.triptico.com/software/grutatxt.html
http://ettext.taint.org/doc/