spec.txt   spec.txt 
--- ---
标题: CommonMark 规范 标题: CommonMark 规范
作者 作者
- John MacFarlane - John MacFarlane
version: 0.11 version: 0.12
date: 2014-11-10 date: 2014-11-10
... ...
# 引言 # 引言
## 什么是 Markdown？ ## 什么是 Markdown？
Markdown 是一种用于编写结构化文档的纯文本格式， Markdown 是一种用于编写结构化文档的纯文本格式，
基于在电子邮件和 usenet 帖子中用于表示格式的约定。 基于在电子邮件和 usenet 帖子中用于表示格式的约定。
它由 John Gruber 于 2004 年开发，他编写了 它由 John Gruber 于 2004 年开发，他编写了
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and title are given immediately after the link text. In [reference and title are given immediately after the link text. In [reference
links](#reference-links) the destination and title are defined elsewhere links](#reference-links) the destination and title are defined elsewhere
in the document. in the document.
A [link text](@link-text) consists of a sequence of zero or more A [link text](@link-text) consists of a sequence of zero or more
inline elements enclosed by square brackets (`[` and `]`). The inline elements enclosed by square brackets (`[` and `]`). The
following rules apply following rules apply
- Links may not contain other links, at any level of nesting. - Links may not contain other links, at any level of nesting.
- Brackets are allowed in the link text only if (a) they are - Brackets are allowed in the [link text](#link-text) only if (a) they
backslash-escaped or (b) they appear as a matched pair of brackets, are backslash-escaped or (b) they appear as a matched pair of brackets,
with an open bracket `[`, a sequence of zero or more inlines, and with an open bracket `[`, a sequence of zero or more inlines, and
a close bracket `]`. a close bracket `]`.
- Backtick [code spans](#code-span), [autolinks](#autolink), and - Backtick [code spans](#code-span), [autolinks](#autolink), and
raw [HTML tags](#html-tag) bind more tightly raw [HTML tags](#html-tag) bind more tightly
than the brackets in link text. Thus, for example, than the brackets in link text. Thus, for example,
`` [foo`]` `` could not be a link text, since the second `]` `` [foo`]` `` could not be a link text, since the second `]`
is part of a code span. is part of a code span.
- The brackets in link text bind more tightly than markers for - The brackets in link text bind more tightly than markers for
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<p>[foo]<a href="/url1">bar</a></p> <p>[foo]<a href="/url1">bar</a></p>
. .
## Images ## Images
Syntax for images is like the syntax for links, with one Syntax for images is like the syntax for links, with one
difference. Instead of [link text](#link-text), we have an [image difference. Instead of [link text](#link-text), we have an [image
description](@image-description). The rules for this are the description](@image-description). The rules for this are the
same as for [link text](#link-text), except that (a) an same as for [link text](#link-text), except that (a) an
image description starts with `![` rather than `[`, and image description starts with `![` rather than `[`, and
(b) an image description may contain links, but not images (b) an image description may contain links.
(even deeply nested). An image description has inline elements An image description has inline elements
as its contents. When an image is rendered to HTML, as its contents. When an image is rendered to HTML,
this is standardly used as the image's `alt` attribute. this is standardly used as the image's `alt` attribute.
. .
![foo](/url "title") ![foo](/url "title")
. .
<p><img src="/url" alt="foo" title="title" /></p> <p><img src="/url" alt="foo" title="title" /></p>
. .
. .
![foo *bar*] ![foo *bar*]
[foo *bar*]: train.jpg "train & tracks" [foo *bar*]: train.jpg "train & tracks"
. .
<p><img src="train.jpg" alt="foo bar" title="train &amp; tracks" /></p> <p><img src="train.jpg" alt="foo bar" title="train &amp; tracks" /></p>
. .
. .
![foo ![bar](/url)](/url2) ![foo ![bar](/url)](/url2)
. .
<p>![foo <img src="/url" alt="bar" />](/url2)</p> <p><img src="/url2" alt="foo bar" /></p>
. .
. .
![foo [bar](/url)](/url2) ![foo [bar](/url)](/url2)
. .
<p><img src="/url2" alt="foo bar" /></p> <p><img src="/url2" alt="foo bar" /></p>
. .
Though this spec is concerned with parsing, not rendering, it is Though this spec is concerned with parsing, not rendering, it is
recommended that in rendering to HTML, only the plain string content recommended that in rendering to HTML, only the plain string content
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