forked from cadey/xesite
947 lines
31 KiB
HTML
947 lines
31 KiB
HTML
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<h1>Markdown: Syntax</h1>
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<ul id="ProjectSubmenu">
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<li><a href="/projects/markdown/" title="Markdown Project Page">Main</a></li>
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<li><a href="/projects/markdown/basics" title="Markdown Basics">Basics</a></li>
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<li><a class="selected" title="Markdown Syntax Documentation">Syntax</a></li>
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<li><a href="/projects/markdown/license" title="Pricing and License Information">License</a></li>
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<li><a href="/projects/markdown/dingus" title="Online Markdown Web Form">Dingus</a></li>
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</ul>
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<ul>
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<li><a href="#overview">Overview</a>
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<ul>
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<li><a href="#philosophy">Philosophy</a></li>
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<li><a href="#html">Inline HTML</a></li>
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<li><a href="#autoescape">Automatic Escaping for Special Characters</a></li>
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</ul></li>
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<li><a href="#block">Block Elements</a>
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<ul>
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<li><a href="#p">Paragraphs and Line Breaks</a></li>
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<li><a href="#header">Headers</a></li>
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<li><a href="#blockquote">Blockquotes</a></li>
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<li><a href="#list">Lists</a></li>
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<li><a href="#precode">Code Blocks</a></li>
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<li><a href="#hr">Horizontal Rules</a></li>
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</ul></li>
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<li><a href="#span">Span Elements</a>
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<ul>
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<li><a href="#link">Links</a></li>
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<li><a href="#em">Emphasis</a></li>
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<li><a href="#code">Code</a></li>
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<li><a href="#img">Images</a></li>
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</ul></li>
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<li><a href="#misc">Miscellaneous</a>
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<ul>
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<li><a href="#backslash">Backslash Escapes</a></li>
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<li><a href="#autolink">Automatic Links</a></li>
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</ul></li>
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</ul>
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<p><strong>Note:</strong> This document is itself written using Markdown; you
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can <a href="/projects/markdown/syntax.text">see the source for it by adding '.text' to the URL</a>.</p>
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<hr>
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<h2 id="overview">Overview</h2>
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<h3 id="philosophy">Philosophy</h3>
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<p>Markdown is intended to be as easy-to-read and easy-to-write as is feasible.</p>
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<p>Readability, however, is emphasized above all else. A Markdown-formatted
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document should be publishable as-is, as plain text, without looking
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like it's been marked up with tags or formatting instructions. While
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Markdown's syntax has been influenced by several existing text-to-HTML
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filters -- including <a href="http://docutils.sourceforge.net/mirror/setext.html">Setext</a>, <a href="http://www.aaronsw.com/2002/atx/">atx</a>, <a href="http://textism.com/tools/textile/">Textile</a>, <a href="http://docutils.sourceforge.net/rst.html">reStructuredText</a>,
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<a href="http://www.triptico.com/software/grutatxt.html">Grutatext</a>, and <a href="http://ettext.taint.org/doc/">EtText</a> -- the single biggest source of
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inspiration for Markdown's syntax is the format of plain text email.</p>
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<p>To this end, Markdown's syntax is comprised entirely of punctuation
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characters, which punctuation characters have been carefully chosen so
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as to look like what they mean. E.g., asterisks around a word actually
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look like *emphasis*. Markdown lists look like, well, lists. Even
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blockquotes look like quoted passages of text, assuming you've ever
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used email.</p>
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<h3 id="html">Inline HTML</h3>
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<p>Markdown's syntax is intended for one purpose: to be used as a
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format for <em>writing</em> for the web.</p>
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<p>Markdown is not a replacement for HTML, or even close to it. Its
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syntax is very small, corresponding only to a very small subset of
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HTML tags. The idea is <em>not</em> to create a syntax that makes it easier
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to insert HTML tags. In my opinion, HTML tags are already easy to
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insert. The idea for Markdown is to make it easy to read, write, and
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edit prose. HTML is a <em>publishing</em> format; Markdown is a <em>writing</em>
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format. Thus, Markdown's formatting syntax only addresses issues that
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can be conveyed in plain text.</p>
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<p>For any markup that is not covered by Markdown's syntax, you simply
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use HTML itself. There's no need to preface it or delimit it to
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indicate that you're switching from Markdown to HTML; you just use
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the tags.</p>
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<p>The only restrictions are that block-level HTML elements -- e.g. <code><div></code>,
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<code><table></code>, <code><pre></code>, <code><p></code>, etc. -- must be separated from surrounding
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content by blank lines, and the start and end tags of the block should
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not be indented with tabs or spaces. Markdown is smart enough not
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to add extra (unwanted) <code><p></code> tags around HTML block-level tags.</p>
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<p>For example, to add an HTML table to a Markdown article:</p>
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<pre><code>This is a regular paragraph.
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<table>
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<tr>
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<td>Foo</td>
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</tr>
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</table>
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This is another regular paragraph.
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</code></pre>
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<p>Note that Markdown formatting syntax is not processed within block-level
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HTML tags. E.g., you can't use Markdown-style <code>*emphasis*</code> inside an
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HTML block.</p>
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<p>Span-level HTML tags -- e.g. <code><span></code>, <code><cite></code>, or <code><del></code> -- can be
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used anywhere in a Markdown paragraph, list item, or header. If you
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want, you can even use HTML tags instead of Markdown formatting; e.g. if
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you'd prefer to use HTML <code><a></code> or <code><img></code> tags instead of Markdown's
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link or image syntax, go right ahead.</p>
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<p>Unlike block-level HTML tags, Markdown syntax <em>is</em> processed within
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span-level tags.</p>
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<h3 id="autoescape">Automatic Escaping for Special Characters</h3>
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<p>In HTML, there are two characters that demand special treatment: <code><</code>
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and <code>&</code>. Left angle brackets are used to start tags; ampersands are
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used to denote HTML entities. If you want to use them as literal
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characters, you must escape them as entities, e.g. <code>&lt;</code>, and
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<code>&amp;</code>.</p>
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<p>Ampersands in particular are bedeviling for web writers. If you want to
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write about 'AT&T', you need to write '<code>AT&amp;T</code>'. You even need to
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escape ampersands within URLs. Thus, if you want to link to:</p>
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<pre><code>http://images.google.com/images?num=30&q=larry+bird
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</code></pre>
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<p>you need to encode the URL as:</p>
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<pre><code>http://images.google.com/images?num=30&amp;q=larry+bird
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</code></pre>
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<p>in your anchor tag <code>href</code> attribute. Needless to say, this is easy to
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forget, and is probably the single most common source of HTML validation
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errors in otherwise well-marked-up web sites.</p>
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<p>Markdown allows you to use these characters naturally, taking care of
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all the necessary escaping for you. If you use an ampersand as part of
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an HTML entity, it remains unchanged; otherwise it will be translated
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into <code>&amp;</code>.</p>
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<p>So, if you want to include a copyright symbol in your article, you can write:</p>
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<pre><code>&copy;
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</code></pre>
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<p>and Markdown will leave it alone. But if you write:</p>
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<pre><code>AT&T
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</code></pre>
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<p>Markdown will translate it to:</p>
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<pre><code>AT&amp;T
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</code></pre>
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<p>Similarly, because Markdown supports <a href="#html">inline HTML</a>, if you use
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angle brackets as delimiters for HTML tags, Markdown will treat them as
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such. But if you write:</p>
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<pre><code>4 < 5
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</code></pre>
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<p>Markdown will translate it to:</p>
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<pre><code>4 &lt; 5
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</code></pre>
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<p>However, inside Markdown code spans and blocks, angle brackets and
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ampersands are <em>always</em> encoded automatically. This makes it easy to use
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Markdown to write about HTML code. (As opposed to raw HTML, which is a
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terrible format for writing about HTML syntax, because every single <code><</code>
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and <code>&</code> in your example code needs to be escaped.)</p>
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<hr>
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<h2 id="block">Block Elements</h2>
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<h3 id="p">Paragraphs and Line Breaks</h3>
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<p>A paragraph is simply one or more consecutive lines of text, separated
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by one or more blank lines. (A blank line is any line that looks like a
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blank line -- a line containing nothing but spaces or tabs is considered
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blank.) Normal paragraphs should not be intended with spaces or tabs.</p>
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<p>The implication of the "one or more consecutive lines of text" rule is
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that Markdown supports "hard-wrapped" text paragraphs. This differs
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significantly from most other text-to-HTML formatters (including Movable
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Type's "Convert Line Breaks" option) which translate every line break
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character in a paragraph into a <code><br /></code> tag.</p>
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<p>When you <em>do</em> want to insert a <code><br /></code> break tag using Markdown, you
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end a line with two or more spaces, then type return.</p>
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<p>Yes, this takes a tad more effort to create a <code><br /></code>, but a simplistic
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"every line break is a <code><br /></code>" rule wouldn't work for Markdown.
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Markdown's email-style <a href="#blockquote">blockquoting</a> and multi-paragraph <a href="#list">list items</a>
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work best -- and look better -- when you format them with hard breaks.</p>
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<h3 id="header">Headers</h3>
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<p>Markdown supports two styles of headers, <a href="http://docutils.sourceforge.net/mirror/setext.html">Setext</a> and <a href="http://www.aaronsw.com/2002/atx/">atx</a>.</p>
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<p>Setext-style headers are "underlined" using equal signs (for first-level
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headers) and dashes (for second-level headers). For example:</p>
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<pre><code>This is an H1
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=============
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This is an H2
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-------------
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</code></pre>
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<p>Any number of underlining <code>=</code>'s or <code>-</code>'s will work.</p>
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<p>Atx-style headers use 1-6 hash characters at the start of the line,
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corresponding to header levels 1-6. For example:</p>
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<pre><code># This is an H1
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## This is an H2
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###### This is an H6
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</code></pre>
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<p>Optionally, you may "close" atx-style headers. This is purely
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cosmetic -- you can use this if you think it looks better. The
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closing hashes don't even need to match the number of hashes
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used to open the header. (The number of opening hashes
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determines the header level.) :</p>
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<pre><code># This is an H1 #
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## This is an H2 ##
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### This is an H3 ######
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</code></pre>
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<h3 id="blockquote">Blockquotes</h3>
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<p>Markdown uses email-style <code>></code> characters for blockquoting. If you're
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familiar with quoting passages of text in an email message, then you
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know how to create a blockquote in Markdown. It looks best if you hard
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wrap the text and put a <code>></code> before every line:</p>
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<pre><code>> This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
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> consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
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> Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
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>
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> Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
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> id sem consectetuer libero luctus adipiscing.
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</code></pre>
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<p>Markdown allows you to be lazy and only put the <code>></code> before the first
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line of a hard-wrapped paragraph:</p>
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<pre><code>> This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
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consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
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Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
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> Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
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id sem consectetuer libero luctus adipiscing.
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</code></pre>
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<p>Blockquotes can be nested (i.e. a blockquote-in-a-blockquote) by
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adding additional levels of <code>></code>:</p>
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<pre><code>> This is the first level of quoting.
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>
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> > This is nested blockquote.
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>
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> Back to the first level.
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</code></pre>
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<p>Blockquotes can contain other Markdown elements, including headers, lists,
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and code blocks:</p>
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<pre><code>> ## This is a header.
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>
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> 1. This is the first list item.
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> 2. This is the second list item.
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>
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> Here's some example code:
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>
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> return shell_exec("echo $input | $markdown_script");
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</code></pre>
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<p>Any decent text editor should make email-style quoting easy. For
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example, with BBEdit, you can make a selection and choose Increase
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Quote Level from the Text menu.</p>
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<h3 id="list">Lists</h3>
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<p>Markdown supports ordered (numbered) and unordered (bulleted) lists.</p>
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<p>Unordered lists use asterisks, pluses, and hyphens -- interchangably
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-- as list markers:</p>
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<pre><code>* Red
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* Green
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* Blue
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</code></pre>
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<p>is equivalent to:</p>
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<pre><code>+ Red
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+ Green
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+ Blue
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</code></pre>
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<p>and:</p>
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<pre><code>- Red
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- Green
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- Blue
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</code></pre>
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<p>Ordered lists use numbers followed by periods:</p>
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<pre><code>1. Bird
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2. McHale
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3. Parish
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</code></pre>
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<p>It's important to note that the actual numbers you use to mark the
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list have no effect on the HTML output Markdown produces. The HTML
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Markdown produces from the above list is:</p>
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<pre><code><ol>
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<li>Bird</li>
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<li>McHale</li>
|
||
|
|
<li>Parish</li>
|
||
|
|
</ol>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>If you instead wrote the list in Markdown like this:</p>
|
||
|
|
|
||
|
|
<pre><code>1. Bird
|
||
|
|
1. McHale
|
||
|
|
1. Parish
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>or even:</p>
|
||
|
|
|
||
|
|
<pre><code>3. Bird
|
||
|
|
1. McHale
|
||
|
|
8. Parish
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<p>To make lists look nice, you can wrap items with hanging indents:</p>
|
||
|
|
|
||
|
|
<pre><code>* 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.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>But if you want to be lazy, you don't have to:</p>
|
||
|
|
|
||
|
|
<pre><code>* 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.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>If list items are separated by blank lines, Markdown will wrap the
|
||
|
|
items in <code><p></code> tags in the HTML output. For example, this input:</p>
|
||
|
|
|
||
|
|
<pre><code>* Bird
|
||
|
|
* Magic
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will turn into:</p>
|
||
|
|
|
||
|
|
<pre><code><ul>
|
||
|
|
<li>Bird</li>
|
||
|
|
<li>Magic</li>
|
||
|
|
</ul>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>But this:</p>
|
||
|
|
|
||
|
|
<pre><code>* Bird
|
||
|
|
|
||
|
|
* Magic
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will turn into:</p>
|
||
|
|
|
||
|
|
<pre><code><ul>
|
||
|
|
<li><p>Bird</p></li>
|
||
|
|
<li><p>Magic</p></li>
|
||
|
|
</ul>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>List items may consist of multiple paragraphs. Each subsequent
|
||
|
|
paragraph in a list item must be intended by either 4 spaces
|
||
|
|
or one tab:</p>
|
||
|
|
|
||
|
|
<pre><code>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.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>It looks nice if you indent every line of the subsequent
|
||
|
|
paragraphs, but here again, Markdown will allow you to be
|
||
|
|
lazy:</p>
|
||
|
|
|
||
|
|
<pre><code>* 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.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>To put a blockquote within a list item, the blockquote's <code>></code>
|
||
|
|
delimiters need to be indented:</p>
|
||
|
|
|
||
|
|
<pre><code>* A list item with a blockquote:
|
||
|
|
|
||
|
|
> This is a blockquote
|
||
|
|
> inside a list item.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>To put a code block within a list item, the code block needs
|
||
|
|
to be indented <em>twice</em> -- 8 spaces or two tabs:</p>
|
||
|
|
|
||
|
|
<pre><code>* A list item with a code block:
|
||
|
|
|
||
|
|
<code goes here>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>It's worth noting that it's possible to trigger an ordered list by
|
||
|
|
accident, by writing something like this:</p>
|
||
|
|
|
||
|
|
<pre><code>1986. What a great season.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>In other words, a <em>number-period-space</em> sequence at the beginning of a
|
||
|
|
line. To avoid this, you can backslash-escape the period:</p>
|
||
|
|
|
||
|
|
<pre><code>1986\. What a great season.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<h3 id="precode">Code Blocks</h3>
|
||
|
|
|
||
|
|
<p>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 <code><pre></code> and <code><code></code> tags.</p>
|
||
|
|
|
||
|
|
<p>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:</p>
|
||
|
|
|
||
|
|
<pre><code>This is a normal paragraph:
|
||
|
|
|
||
|
|
This is a code block.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Markdown will generate:</p>
|
||
|
|
|
||
|
|
<pre><code><p>This is a normal paragraph:</p>
|
||
|
|
|
||
|
|
<pre><code>This is a code block.
|
||
|
|
</code></pre>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>One level of indentation -- 4 spaces or 1 tab -- is removed from each
|
||
|
|
line of the code block. For example, this:</p>
|
||
|
|
|
||
|
|
<pre><code>Here is an example of AppleScript:
|
||
|
|
|
||
|
|
tell application "Foo"
|
||
|
|
beep
|
||
|
|
end tell
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will turn into:</p>
|
||
|
|
|
||
|
|
<pre><code><p>Here is an example of AppleScript:</p>
|
||
|
|
|
||
|
|
<pre><code>tell application "Foo"
|
||
|
|
beep
|
||
|
|
end tell
|
||
|
|
</code></pre>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>A code block continues until it reaches a line that is not indented
|
||
|
|
(or the end of the article).</p>
|
||
|
|
|
||
|
|
<p>Within a code block, ampersands (<code>&</code>) and angle brackets (<code><</code> and <code>></code>)
|
||
|
|
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:</p>
|
||
|
|
|
||
|
|
<pre><code> <div class="footer">
|
||
|
|
&copy; 2004 Foo Corporation
|
||
|
|
</div>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will turn into:</p>
|
||
|
|
|
||
|
|
<pre><code><pre><code>&lt;div class="footer"&gt;
|
||
|
|
&amp;copy; 2004 Foo Corporation
|
||
|
|
&lt;/div&gt;
|
||
|
|
</code></pre>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<h3 id="hr">Horizontal Rules</h3>
|
||
|
|
|
||
|
|
<p>You can produce a horizontal rule tag (<code><hr /></code>) 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:</p>
|
||
|
|
|
||
|
|
<pre><code>* * *
|
||
|
|
|
||
|
|
***
|
||
|
|
|
||
|
|
*****
|
||
|
|
|
||
|
|
- - -
|
||
|
|
|
||
|
|
---------------------------------------
|
||
|
|
|
||
|
|
_ _ _
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
|
||
|
|
<h2 id="span">Span Elements</h2>
|
||
|
|
|
||
|
|
<h3 id="link">Links</h3>
|
||
|
|
|
||
|
|
<p>Markdown supports two style of links: <em>inline</em> and <em>reference</em>.</p>
|
||
|
|
|
||
|
|
<p>In both styles, the link text is delimited by [square brackets].</p>
|
||
|
|
|
||
|
|
<p>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 <em>optional</em>
|
||
|
|
title for the link, surrounded in quotes. For example:</p>
|
||
|
|
|
||
|
|
<pre><code>This is [an example](http://example.com/ "Title") inline link.
|
||
|
|
|
||
|
|
[This link](http://example.net/) has no title attribute.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Will produce:</p>
|
||
|
|
|
||
|
|
<pre><code><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>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>If you're referring to a local resource on the same server, you can
|
||
|
|
use relative paths:</p>
|
||
|
|
|
||
|
|
<pre><code>See my [About](/about/) page for details.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Reference-style links use a second set of square brackets, inside
|
||
|
|
which you place a label of your choosing to identify the link:</p>
|
||
|
|
|
||
|
|
<pre><code>This is [an example][id] reference-style link.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>You can optionally use a space to separate the sets of brackets:</p>
|
||
|
|
|
||
|
|
<pre><code>This is [an example] [id] reference-style link.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Then, anywhere in the document, you define your link label like this,
|
||
|
|
on a line by itself:</p>
|
||
|
|
|
||
|
|
<pre><code>[id]: http://example.com/ "Optional Title Here"
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>That is:</p>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>Square brackets containing the link identifier (optionally
|
||
|
|
indented from the left margin using up to three spaces);</li>
|
||
|
|
<li>followed by a colon;</li>
|
||
|
|
<li>followed by one or more spaces (or tabs);</li>
|
||
|
|
<li>followed by the URL for the link;</li>
|
||
|
|
<li>optionally followed by a title attribute for the link, enclosed
|
||
|
|
in double or single quotes.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>The link URL may, optionally, be surrounded by angle brackets:</p>
|
||
|
|
|
||
|
|
<pre><code>[id]: <http://example.com/> "Optional Title Here"
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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:</p>
|
||
|
|
|
||
|
|
<pre><code>[id]: http://example.com/longish/path/to/resource/here
|
||
|
|
"Optional Title Here"
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Link definitions are only used for creating links during Markdown
|
||
|
|
processing, and are stripped from your document in the HTML output.</p>
|
||
|
|
|
||
|
|
<p>Link definition names may constist of letters, numbers, spaces, and punctuation -- but they are <em>not</em> case sensitive. E.g. these two links:</p>
|
||
|
|
|
||
|
|
<pre><code>[link text][a]
|
||
|
|
[link text][A]
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>are equivalent.</p>
|
||
|
|
|
||
|
|
<p>The <em>implicit link name</em> 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
|
||
|
|
"Google" to the google.com web site, you could simply write:</p>
|
||
|
|
|
||
|
|
<pre><code>[Google][]
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>And then define the link:</p>
|
||
|
|
|
||
|
|
<pre><code>[Google]: http://google.com/
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Because link names may contain spaces, this shortcut even works for
|
||
|
|
multiple words in the link text:</p>
|
||
|
|
|
||
|
|
<pre><code>Visit [Daring Fireball][] for more information.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>And then define the link:</p>
|
||
|
|
|
||
|
|
<pre><code>[Daring Fireball]: http://daringfireball.net/
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<p>Here's an example of reference links in action:</p>
|
||
|
|
|
||
|
|
<pre><code>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"
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Using the implicit link name shortcut, you could instead write:</p>
|
||
|
|
|
||
|
|
<pre><code>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"
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Both of the above examples will produce the following HTML output:</p>
|
||
|
|
|
||
|
|
<pre><code><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>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>For comparison, here is the same paragraph written using
|
||
|
|
Markdown's inline link style:</p>
|
||
|
|
|
||
|
|
<pre><code>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").
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<h3 id="em">Emphasis</h3>
|
||
|
|
|
||
|
|
<p>Markdown treats asterisks (<code>*</code>) and underscores (<code>_</code>) as indicators of
|
||
|
|
emphasis. Text wrapped with one <code>*</code> or <code>_</code> will be wrapped with an
|
||
|
|
HTML <code><em></code> tag; double <code>*</code>'s or <code>_</code>'s will be wrapped with an HTML
|
||
|
|
<code><strong></code> tag. E.g., this input:</p>
|
||
|
|
|
||
|
|
<pre><code>*single asterisks*
|
||
|
|
|
||
|
|
_single underscores_
|
||
|
|
|
||
|
|
**double asterisks**
|
||
|
|
|
||
|
|
__double underscores__
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will produce:</p>
|
||
|
|
|
||
|
|
<pre><code><em>single asterisks</em>
|
||
|
|
|
||
|
|
<em>single underscores</em>
|
||
|
|
|
||
|
|
<strong>double asterisks</strong>
|
||
|
|
|
||
|
|
<strong>double underscores</strong>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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.</p>
|
||
|
|
|
||
|
|
<p>Emphasis can be used in the middle of a word:</p>
|
||
|
|
|
||
|
|
<pre><code>un*fucking*believable
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>But if you surround an <code>*</code> or <code>_</code> with spaces, it'll be treated as a
|
||
|
|
literal asterisk or underscore.</p>
|
||
|
|
|
||
|
|
<p>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:</p>
|
||
|
|
|
||
|
|
<pre><code>\*this text is surrounded by literal asterisks\*
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<h3 id="code">Code</h3>
|
||
|
|
|
||
|
|
<p>To indicate a span of code, wrap it with backtick quotes (<code>`</code>).
|
||
|
|
Unlike a pre-formatted code block, a code span indicates code within a
|
||
|
|
normal paragraph. For example:</p>
|
||
|
|
|
||
|
|
<pre><code>Use the `printf()` function.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will produce:</p>
|
||
|
|
|
||
|
|
<pre><code><p>Use the <code>printf()</code> function.</p>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>To include a literal backtick character within a code span, you can use
|
||
|
|
multiple backticks as the opening and closing delimiters:</p>
|
||
|
|
|
||
|
|
<pre><code>``There is a literal backtick (`) here.``
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>which will produce this:</p>
|
||
|
|
|
||
|
|
<pre><code><p><code>There is a literal backtick (`) here.</code></p>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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:</p>
|
||
|
|
|
||
|
|
<pre><code>A single backtick in a code span: `` ` ``
|
||
|
|
|
||
|
|
A backtick-delimited string in a code span: `` `foo` ``
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>will produce:</p>
|
||
|
|
|
||
|
|
<pre><code><p>A single backtick in a code span: <code>`</code></p>
|
||
|
|
|
||
|
|
<p>A backtick-delimited string in a code span: <code>`foo`</code></p>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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:</p>
|
||
|
|
|
||
|
|
<pre><code>Please don't use any `<blink>` tags.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>into:</p>
|
||
|
|
|
||
|
|
<pre><code><p>Please don't use any <code>&lt;blink&gt;</code> tags.</p>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>You can write this:</p>
|
||
|
|
|
||
|
|
<pre><code>`&#8212;` is the decimal-encoded equivalent of `&mdash;`.
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>to produce:</p>
|
||
|
|
|
||
|
|
<pre><code><p><code>&amp;#8212;</code> is the decimal-encoded
|
||
|
|
equivalent of <code>&amp;mdash;</code>.</p>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<h3 id="img">Images</h3>
|
||
|
|
|
||
|
|
<p>Admittedly, it's fairly difficult to devise a "natural" syntax for
|
||
|
|
placing images into a plain text document format.</p>
|
||
|
|
|
||
|
|
<p>Markdown uses an image syntax that is intended to resemble the syntax
|
||
|
|
for links, allowing for two styles: <em>inline</em> and <em>reference</em>.</p>
|
||
|
|
|
||
|
|
<p>Inline image syntax looks like this:</p>
|
||
|
|
|
||
|
|
<pre><code>
|
||
|
|
|
||
|
|
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>That is:</p>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>An exclamation mark: <code>!</code>;</li>
|
||
|
|
<li>followed by a set of square brackets, containing the <code>alt</code>
|
||
|
|
attribute text for the image;</li>
|
||
|
|
<li>followed by a set of parentheses, containing the URL or path to
|
||
|
|
the image, and an optional <code>title</code> attribute enclosed in double
|
||
|
|
or single quotes.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<p>Reference-style image syntax looks like this:</p>
|
||
|
|
|
||
|
|
<pre><code>![Alt text][id]
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Where "id" is the name of a defined image reference. Image references
|
||
|
|
are defined using syntax identical to link references:</p>
|
||
|
|
|
||
|
|
<pre><code>[id]: url/to/image "Optional title attribute"
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>As of this writing, Markdown has no syntax for specifying the
|
||
|
|
dimensions of an image; if this is important to you, you can simply
|
||
|
|
use regular HTML <code><img></code> tags.</p>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
|
||
|
|
<h2 id="misc">Miscellaneous</h2>
|
||
|
|
|
||
|
|
<h3 id="autolink">Automatic Links</h3>
|
||
|
|
|
||
|
|
<p>Markdown supports a shortcut style for creating "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 show the actual text of a URL or email address, and also have it be a clickable link, you can do this:</p>
|
||
|
|
|
||
|
|
<pre><code><http://example.com/>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Markdown will turn this into:</p>
|
||
|
|
|
||
|
|
<pre><code><a href="http://example.com/">http://example.com/</a>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>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:</p>
|
||
|
|
|
||
|
|
<pre><code><address@example.com>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>into something like this:</p>
|
||
|
|
|
||
|
|
<pre><code><a href="&#x6D;&#x61;i&#x6C;&#x74;&#x6F;:&#x61;&#x64;&#x64;&#x72;&#x65;
|
||
|
|
&#115;&#115;&#64;&#101;&#120;&#x61;&#109;&#x70;&#x6C;e&#x2E;&#99;&#111;
|
||
|
|
&#109;">&#x61;&#x64;&#x64;&#x72;&#x65;&#115;&#115;&#64;&#101;&#120;&#x61;
|
||
|
|
&#109;&#x70;&#x6C;e&#x2E;&#99;&#111;&#109;</a>
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>which will render in a browser as a clickable link to "address@example.com".</p>
|
||
|
|
|
||
|
|
<p>(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.)</p>
|
||
|
|
|
||
|
|
<h3 id="backslash">Backslash Escapes</h3>
|
||
|
|
|
||
|
|
<p>Markdown 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 <code><em></code> tag), you can backslashes
|
||
|
|
before the asterisks, like this:</p>
|
||
|
|
|
||
|
|
<pre><code>\*literal asterisks\*
|
||
|
|
</code></pre>
|
||
|
|
|
||
|
|
<p>Markdown provides backslash escapes for the following characters:</p>
|
||
|
|
|
||
|
|
<pre><code>\ backslash
|
||
|
|
` backtick
|
||
|
|
* asterisk
|
||
|
|
_ underscore
|
||
|
|
{} curly braces
|
||
|
|
[] square brackets
|
||
|
|
() parentheses
|
||
|
|
# hash mark
|
||
|
|
+ plus sign
|
||
|
|
- minus sign (hyphen)
|
||
|
|
. dot
|
||
|
|
! exclamation mark
|
||
|
|
</code></pre>
|