github.com/insionng/yougam@v0.0.0-20170714101924-2bc18d833463/libraries/russross/blackfriday/testdata/Markdown Documentation - Syntax.text (about)

     1  Markdown: Syntax
     2  ================
     3  
     4  <ul id="ProjectSubmenu">
     5      <li><a href="/projects/markdown/" title="Markdown Project Page">Main</a></li>
     6      <li><a href="/projects/markdown/basics" title="Markdown Basics">Basics</a></li>
     7      <li><a class="selected" title="Markdown Syntax Documentation">Syntax</a></li>
     8      <li><a href="/projects/markdown/license" title="Pricing and License Information">License</a></li>
     9      <li><a href="/projects/markdown/dingus" title="Online Markdown Web Form">Dingus</a></li>
    10  </ul>
    11  
    12  
    13  *   [Overview](#overview)
    14      *   [Philosophy](#philosophy)
    15      *   [Inline HTML](#html)
    16      *   [Automatic Escaping for Special Characters](#autoescape)
    17  *   [Block Elements](#block)
    18      *   [Paragraphs and Line Breaks](#p)
    19      *   [Headers](#header)
    20      *   [Blockquotes](#blockquote)
    21      *   [Lists](#list)
    22      *   [Code Blocks](#precode)
    23      *   [Horizontal Rules](#hr)
    24  *   [Span Elements](#span)
    25      *   [Links](#link)
    26      *   [Emphasis](#em)
    27      *   [Code](#code)
    28      *   [Images](#img)
    29  *   [Miscellaneous](#misc)
    30      *   [Backslash Escapes](#backslash)
    31      *   [Automatic Links](#autolink)
    32  
    33  
    34  **Note:** This document is itself written using Markdown; you
    35  can [see the source for it by adding '.text' to the URL][src].
    36  
    37    [src]: /projects/markdown/syntax.text
    38  
    39  * * *
    40  
    41  <h2 id="overview">Overview</h2>
    42  
    43  <h3 id="philosophy">Philosophy</h3>
    44  
    45  Markdown is intended to be as easy-to-read and easy-to-write as is feasible.
    46  
    47  Readability, however, is emphasized above all else. A Markdown-formatted
    48  document should be publishable as-is, as plain text, without looking
    49  like it's been marked up with tags or formatting instructions. While
    50  Markdown's syntax has been influenced by several existing text-to-HTML
    51  filters -- including [Setext] [1], [atx] [2], [Textile] [3], [reStructuredText] [4],
    52  [Grutatext] [5], and [EtText] [6] -- the single biggest source of
    53  inspiration for Markdown's syntax is the format of plain text email.
    54  
    55    [1]: http://docutils.sourceforge.net/mirror/setext.html
    56    [2]: http://www.aaronsw.com/2002/atx/
    57    [3]: http://textism.com/tools/textile/
    58    [4]: http://docutils.sourceforge.net/rst.html
    59    [5]: http://www.triptico.com/software/grutatxt.html
    60    [6]: http://ettext.taint.org/doc/
    61  
    62  To this end, Markdown's syntax is comprised entirely of punctuation
    63  characters, which punctuation characters have been carefully chosen so
    64  as to look like what they mean. E.g., asterisks around a word actually
    65  look like \*emphasis\*. Markdown lists look like, well, lists. Even
    66  blockquotes look like quoted passages of text, assuming you've ever
    67  used email.
    68  
    69  
    70  
    71  <h3 id="html">Inline HTML</h3>
    72  
    73  Markdown's syntax is intended for one purpose: to be used as a
    74  format for *writing* for the web.
    75  
    76  Markdown is not a replacement for HTML, or even close to it. Its
    77  syntax is very small, corresponding only to a very small subset of
    78  HTML tags. The idea is *not* to create a syntax that makes it easier
    79  to insert HTML tags. In my opinion, HTML tags are already easy to
    80  insert. The idea for Markdown is to make it easy to read, write, and
    81  edit prose. HTML is a *publishing* format; Markdown is a *writing*
    82  format. Thus, Markdown's formatting syntax only addresses issues that
    83  can be conveyed in plain text.
    84  
    85  For any markup that is not covered by Markdown's syntax, you simply
    86  use HTML itself. There's no need to preface it or delimit it to
    87  indicate that you're switching from Markdown to HTML; you just use
    88  the tags.
    89  
    90  The only restrictions are that block-level HTML elements -- e.g. `<div>`,
    91  `<table>`, `<pre>`, `<p>`, etc. -- must be separated from surrounding
    92  content by blank lines, and the start and end tags of the block should
    93  not be indented with tabs or spaces. Markdown is smart enough not
    94  to add extra (unwanted) `<p>` tags around HTML block-level tags.
    95  
    96  For example, to add an HTML table to a Markdown article:
    97  
    98      This is a regular paragraph.
    99  
   100      <table>
   101          <tr>
   102              <td>Foo</td>
   103          </tr>
   104      </table>
   105  
   106      This is another regular paragraph.
   107  
   108  Note that Markdown formatting syntax is not processed within block-level
   109  HTML tags. E.g., you can't use Markdown-style `*emphasis*` inside an
   110  HTML block.
   111  
   112  Span-level HTML tags -- e.g. `<span>`, `<cite>`, or `<del>` -- can be
   113  used anywhere in a Markdown paragraph, list item, or header. If you
   114  want, you can even use HTML tags instead of Markdown formatting; e.g. if
   115  you'd prefer to use HTML `<a>` or `<img>` tags instead of Markdown's
   116  link or image syntax, go right ahead.
   117  
   118  Unlike block-level HTML tags, Markdown syntax *is* processed within
   119  span-level tags.
   120  
   121  
   122  <h3 id="autoescape">Automatic Escaping for Special Characters</h3>
   123  
   124  In HTML, there are two characters that demand special treatment: `<`
   125  and `&`. Left angle brackets are used to start tags; ampersands are
   126  used to denote HTML entities. If you want to use them as literal
   127  characters, you must escape them as entities, e.g. `&lt;`, and
   128  `&amp;`.
   129  
   130  Ampersands in particular are bedeviling for web writers. If you want to
   131  write about 'AT&T', you need to write '`AT&amp;T`'. You even need to
   132  escape ampersands within URLs. Thus, if you want to link to:
   133  
   134      http://images.google.com/images?num=30&q=larry+bird
   135  
   136  you need to encode the URL as:
   137  
   138      http://images.google.com/images?num=30&amp;q=larry+bird
   139  
   140  in your anchor tag `href` attribute. Needless to say, this is easy to
   141  forget, and is probably the single most common source of HTML validation
   142  errors in otherwise well-marked-up web sites.
   143  
   144  Markdown allows you to use these characters naturally, taking care of
   145  all the necessary escaping for you. If you use an ampersand as part of
   146  an HTML entity, it remains unchanged; otherwise it will be translated
   147  into `&amp;`.
   148  
   149  So, if you want to include a copyright symbol in your article, you can write:
   150  
   151      &copy;
   152  
   153  and Markdown will leave it alone. But if you write:
   154  
   155      AT&T
   156  
   157  Markdown will translate it to:
   158  
   159      AT&amp;T
   160  
   161  Similarly, because Markdown supports [inline HTML](#html), if you use
   162  angle brackets as delimiters for HTML tags, Markdown will treat them as
   163  such. But if you write:
   164  
   165      4 < 5
   166  
   167  Markdown will translate it to:
   168  
   169      4 &lt; 5
   170  
   171  However, inside Markdown code spans and blocks, angle brackets and
   172  ampersands are *always* encoded automatically. This makes it easy to use
   173  Markdown to write about HTML code. (As opposed to raw HTML, which is a
   174  terrible format for writing about HTML syntax, because every single `<`
   175  and `&` in your example code needs to be escaped.)
   176  
   177  
   178  * * *
   179  
   180  
   181  <h2 id="block">Block Elements</h2>
   182  
   183  
   184  <h3 id="p">Paragraphs and Line Breaks</h3>
   185  
   186  A paragraph is simply one or more consecutive lines of text, separated
   187  by one or more blank lines. (A blank line is any line that looks like a
   188  blank line -- a line containing nothing but spaces or tabs is considered
   189  blank.) Normal paragraphs should not be intended with spaces or tabs.
   190  
   191  The implication of the "one or more consecutive lines of text" rule is
   192  that Markdown supports "hard-wrapped" text paragraphs. This differs
   193  significantly from most other text-to-HTML formatters (including Movable
   194  Type's "Convert Line Breaks" option) which translate every line break
   195  character in a paragraph into a `<br />` tag.
   196  
   197  When you *do* want to insert a `<br />` break tag using Markdown, you
   198  end a line with two or more spaces, then type return.
   199  
   200  Yes, this takes a tad more effort to create a `<br />`, but a simplistic
   201  "every line break is a `<br />`" rule wouldn't work for Markdown.
   202  Markdown's email-style [blockquoting][bq] and multi-paragraph [list items][l]
   203  work best -- and look better -- when you format them with hard breaks.
   204  
   205    [bq]: #blockquote
   206    [l]:  #list
   207  
   208  
   209  
   210  <h3 id="header">Headers</h3>
   211  
   212  Markdown supports two styles of headers, [Setext] [1] and [atx] [2].
   213  
   214  Setext-style headers are "underlined" using equal signs (for first-level
   215  headers) and dashes (for second-level headers). For example:
   216  
   217      This is an H1
   218      =============
   219  
   220      This is an H2
   221      -------------
   222  
   223  Any number of underlining `=`'s or `-`'s will work.
   224  
   225  Atx-style headers use 1-6 hash characters at the start of the line,
   226  corresponding to header levels 1-6. For example:
   227  
   228      # This is an H1
   229  
   230      ## This is an H2
   231  
   232      ###### This is an H6
   233  
   234  Optionally, you may "close" atx-style headers. This is purely
   235  cosmetic -- you can use this if you think it looks better. The
   236  closing hashes don't even need to match the number of hashes
   237  used to open the header. (The number of opening hashes
   238  determines the header level.) :
   239  
   240      # This is an H1 #
   241  
   242      ## This is an H2 ##
   243  
   244      ### This is an H3 ######
   245  
   246  
   247  <h3 id="blockquote">Blockquotes</h3>
   248  
   249  Markdown uses email-style `>` characters for blockquoting. If you're
   250  familiar with quoting passages of text in an email message, then you
   251  know how to create a blockquote in Markdown. It looks best if you hard
   252  wrap the text and put a `>` before every line:
   253  
   254      > This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
   255      > consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
   256      > Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
   257      > 
   258      > Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
   259      > id sem consectetuer libero luctus adipiscing.
   260  
   261  Markdown allows you to be lazy and only put the `>` before the first
   262  line of a hard-wrapped paragraph:
   263  
   264      > This is a blockquote with two paragraphs. Lorem ipsum dolor sit amet,
   265      consectetuer adipiscing elit. Aliquam hendrerit mi posuere lectus.
   266      Vestibulum enim wisi, viverra nec, fringilla in, laoreet vitae, risus.
   267  
   268      > Donec sit amet nisl. Aliquam semper ipsum sit amet velit. Suspendisse
   269      id sem consectetuer libero luctus adipiscing.
   270  
   271  Blockquotes can be nested (i.e. a blockquote-in-a-blockquote) by
   272  adding additional levels of `>`:
   273  
   274      > This is the first level of quoting.
   275      >
   276      > > This is nested blockquote.
   277      >
   278      > Back to the first level.
   279  
   280  Blockquotes can contain other Markdown elements, including headers, lists,
   281  and code blocks:
   282  
   283  	> ## This is a header.
   284  	> 
   285  	> 1.   This is the first list item.
   286  	> 2.   This is the second list item.
   287  	> 
   288  	> Here's some example code:
   289  	> 
   290  	>     return shell_exec("echo $input | $markdown_script");
   291  
   292  Any decent text editor should make email-style quoting easy. For
   293  example, with BBEdit, you can make a selection and choose Increase
   294  Quote Level from the Text menu.
   295  
   296  
   297  <h3 id="list">Lists</h3>
   298  
   299  Markdown supports ordered (numbered) and unordered (bulleted) lists.
   300  
   301  Unordered lists use asterisks, pluses, and hyphens -- interchangably
   302  -- as list markers:
   303  
   304      *   Red
   305      *   Green
   306      *   Blue
   307  
   308  is equivalent to:
   309  
   310      +   Red
   311      +   Green
   312      +   Blue
   313  
   314  and:
   315  
   316      -   Red
   317      -   Green
   318      -   Blue
   319  
   320  Ordered lists use numbers followed by periods:
   321  
   322      1.  Bird
   323      2.  McHale
   324      3.  Parish
   325  
   326  It's important to note that the actual numbers you use to mark the
   327  list have no effect on the HTML output Markdown produces. The HTML
   328  Markdown produces from the above list is:
   329  
   330      <ol>
   331      <li>Bird</li>
   332      <li>McHale</li>
   333      <li>Parish</li>
   334      </ol>
   335  
   336  If you instead wrote the list in Markdown like this:
   337  
   338      1.  Bird
   339      1.  McHale
   340      1.  Parish
   341  
   342  or even:
   343  
   344      3. Bird
   345      1. McHale
   346      8. Parish
   347  
   348  you'd get the exact same HTML output. The point is, if you want to,
   349  you can use ordinal numbers in your ordered Markdown lists, so that
   350  the numbers in your source match the numbers in your published HTML.
   351  But if you want to be lazy, you don't have to.
   352  
   353  If you do use lazy list numbering, however, you should still start the
   354  list with the number 1. At some point in the future, Markdown may support
   355  starting ordered lists at an arbitrary number.
   356  
   357  List markers typically start at the left margin, but may be indented by
   358  up to three spaces. List markers must be followed by one or more spaces
   359  or a tab.
   360  
   361  To make lists look nice, you can wrap items with hanging indents:
   362  
   363      *   Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
   364          Aliquam hendrerit mi posuere lectus. Vestibulum enim wisi,
   365          viverra nec, fringilla in, laoreet vitae, risus.
   366      *   Donec sit amet nisl. Aliquam semper ipsum sit amet velit.
   367          Suspendisse id sem consectetuer libero luctus adipiscing.
   368  
   369  But if you want to be lazy, you don't have to:
   370  
   371      *   Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
   372      Aliquam hendrerit mi posuere lectus. Vestibulum enim wisi,
   373      viverra nec, fringilla in, laoreet vitae, risus.
   374      *   Donec sit amet nisl. Aliquam semper ipsum sit amet velit.
   375      Suspendisse id sem consectetuer libero luctus adipiscing.
   376  
   377  If list items are separated by blank lines, Markdown will wrap the
   378  items in `<p>` tags in the HTML output. For example, this input:
   379  
   380      *   Bird
   381      *   Magic
   382  
   383  will turn into:
   384  
   385      <ul>
   386      <li>Bird</li>
   387      <li>Magic</li>
   388      </ul>
   389  
   390  But this:
   391  
   392      *   Bird
   393  
   394      *   Magic
   395  
   396  will turn into:
   397  
   398      <ul>
   399      <li><p>Bird</p></li>
   400      <li><p>Magic</p></li>
   401      </ul>
   402  
   403  List items may consist of multiple paragraphs. Each subsequent
   404  paragraph in a list item must be intended by either 4 spaces
   405  or one tab:
   406  
   407      1.  This is a list item with two paragraphs. Lorem ipsum dolor
   408          sit amet, consectetuer adipiscing elit. Aliquam hendrerit
   409          mi posuere lectus.
   410  
   411          Vestibulum enim wisi, viverra nec, fringilla in, laoreet
   412          vitae, risus. Donec sit amet nisl. Aliquam semper ipsum
   413          sit amet velit.
   414  
   415      2.  Suspendisse id sem consectetuer libero luctus adipiscing.
   416  
   417  It looks nice if you indent every line of the subsequent
   418  paragraphs, but here again, Markdown will allow you to be
   419  lazy:
   420  
   421      *   This is a list item with two paragraphs.
   422  
   423          This is the second paragraph in the list item. You're
   424      only required to indent the first line. Lorem ipsum dolor
   425      sit amet, consectetuer adipiscing elit.
   426  
   427      *   Another item in the same list.
   428  
   429  To put a blockquote within a list item, the blockquote's `>`
   430  delimiters need to be indented:
   431  
   432      *   A list item with a blockquote:
   433  
   434          > This is a blockquote
   435          > inside a list item.
   436  
   437  To put a code block within a list item, the code block needs
   438  to be indented *twice* -- 8 spaces or two tabs:
   439  
   440      *   A list item with a code block:
   441  
   442              <code goes here>
   443  
   444  
   445  It's worth noting that it's possible to trigger an ordered list by
   446  accident, by writing something like this:
   447  
   448      1986. What a great season.
   449  
   450  In other words, a *number-period-space* sequence at the beginning of a
   451  line. To avoid this, you can backslash-escape the period:
   452  
   453      1986\. What a great season.
   454  
   455  
   456  
   457  <h3 id="precode">Code Blocks</h3>
   458  
   459  Pre-formatted code blocks are used for writing about programming or
   460  markup source code. Rather than forming normal paragraphs, the lines
   461  of a code block are interpreted literally. Markdown wraps a code block
   462  in both `<pre>` and `<code>` tags.
   463  
   464  To produce a code block in Markdown, simply indent every line of the
   465  block by at least 4 spaces or 1 tab. For example, given this input:
   466  
   467      This is a normal paragraph:
   468  
   469          This is a code block.
   470  
   471  Markdown will generate:
   472  
   473      <p>This is a normal paragraph:</p>
   474  
   475      <pre><code>This is a code block.
   476      </code></pre>
   477  
   478  One level of indentation -- 4 spaces or 1 tab -- is removed from each
   479  line of the code block. For example, this:
   480  
   481      Here is an example of AppleScript:
   482  
   483          tell application "Foo"
   484              beep
   485          end tell
   486  
   487  will turn into:
   488  
   489      <p>Here is an example of AppleScript:</p>
   490  
   491      <pre><code>tell application "Foo"
   492          beep
   493      end tell
   494      </code></pre>
   495  
   496  A code block continues until it reaches a line that is not indented
   497  (or the end of the article).
   498  
   499  Within a code block, ampersands (`&`) and angle brackets (`<` and `>`)
   500  are automatically converted into HTML entities. This makes it very
   501  easy to include example HTML source code using Markdown -- just paste
   502  it and indent it, and Markdown will handle the hassle of encoding the
   503  ampersands and angle brackets. For example, this:
   504  
   505          <div class="footer">
   506              &copy; 2004 Foo Corporation
   507          </div>
   508  
   509  will turn into:
   510  
   511      <pre><code>&lt;div class="footer"&gt;
   512          &amp;copy; 2004 Foo Corporation
   513      &lt;/div&gt;
   514      </code></pre>
   515  
   516  Regular Markdown syntax is not processed within code blocks. E.g.,
   517  asterisks are just literal asterisks within a code block. This means
   518  it's also easy to use Markdown to write about Markdown's own syntax.
   519  
   520  
   521  
   522  <h3 id="hr">Horizontal Rules</h3>
   523  
   524  You can produce a horizontal rule tag (`<hr />`) by placing three or
   525  more hyphens, asterisks, or underscores on a line by themselves. If you
   526  wish, you may use spaces between the hyphens or asterisks. Each of the
   527  following lines will produce a horizontal rule:
   528  
   529      * * *
   530  
   531      ***
   532  
   533      *****
   534  	
   535      - - -
   536  
   537      ---------------------------------------
   538  
   539  	_ _ _
   540  
   541  
   542  * * *
   543  
   544  <h2 id="span">Span Elements</h2>
   545  
   546  <h3 id="link">Links</h3>
   547  
   548  Markdown supports two style of links: *inline* and *reference*.
   549  
   550  In both styles, the link text is delimited by [square brackets].
   551  
   552  To create an inline link, use a set of regular parentheses immediately
   553  after the link text's closing square bracket. Inside the parentheses,
   554  put the URL where you want the link to point, along with an *optional*
   555  title for the link, surrounded in quotes. For example:
   556  
   557      This is [an example](http://example.com/ "Title") inline link.
   558  
   559      [This link](http://example.net/) has no title attribute.
   560  
   561  Will produce:
   562  
   563      <p>This is <a href="http://example.com/" title="Title">
   564      an example</a> inline link.</p>
   565  
   566      <p><a href="http://example.net/">This link</a> has no
   567      title attribute.</p>
   568  
   569  If you're referring to a local resource on the same server, you can
   570  use relative paths:
   571  
   572      See my [About](/about/) page for details.
   573  
   574  Reference-style links use a second set of square brackets, inside
   575  which you place a label of your choosing to identify the link:
   576  
   577      This is [an example][id] reference-style link.
   578  
   579  You can optionally use a space to separate the sets of brackets:
   580  
   581      This is [an example] [id] reference-style link.
   582  
   583  Then, anywhere in the document, you define your link label like this,
   584  on a line by itself:
   585  
   586      [id]: http://example.com/  "Optional Title Here"
   587  
   588  That is:
   589  
   590  *   Square brackets containing the link identifier (optionally
   591      indented from the left margin using up to three spaces);
   592  *   followed by a colon;
   593  *   followed by one or more spaces (or tabs);
   594  *   followed by the URL for the link;
   595  *   optionally followed by a title attribute for the link, enclosed
   596      in double or single quotes.
   597  
   598  The link URL may, optionally, be surrounded by angle brackets:
   599  
   600      [id]: <http://example.com/>  "Optional Title Here"
   601  
   602  You can put the title attribute on the next line and use extra spaces
   603  or tabs for padding, which tends to look better with longer URLs:
   604  
   605      [id]: http://example.com/longish/path/to/resource/here
   606          "Optional Title Here"
   607  
   608  Link definitions are only used for creating links during Markdown
   609  processing, and are stripped from your document in the HTML output.
   610  
   611  Link definition names may constist of letters, numbers, spaces, and punctuation -- but they are *not* case sensitive. E.g. these two links:
   612  
   613  	[link text][a]
   614  	[link text][A]
   615  
   616  are equivalent.
   617  
   618  The *implicit link name* shortcut allows you to omit the name of the
   619  link, in which case the link text itself is used as the name.
   620  Just use an empty set of square brackets -- e.g., to link the word
   621  "Google" to the google.com web site, you could simply write:
   622  
   623  	[Google][]
   624  
   625  And then define the link:
   626  
   627  	[Google]: http://google.com/
   628  
   629  Because link names may contain spaces, this shortcut even works for
   630  multiple words in the link text:
   631  
   632  	Visit [Daring Fireball][] for more information.
   633  
   634  And then define the link:
   635  	
   636  	[Daring Fireball]: http://daringfireball.net/
   637  
   638  Link definitions can be placed anywhere in your Markdown document. I
   639  tend to put them immediately after each paragraph in which they're
   640  used, but if you want, you can put them all at the end of your
   641  document, sort of like footnotes.
   642  
   643  Here's an example of reference links in action:
   644  
   645      I get 10 times more traffic from [Google] [1] than from
   646      [Yahoo] [2] or [MSN] [3].
   647  
   648        [1]: http://google.com/        "Google"
   649        [2]: http://search.yahoo.com/  "Yahoo Search"
   650        [3]: http://search.msn.com/    "MSN Search"
   651  
   652  Using the implicit link name shortcut, you could instead write:
   653  
   654      I get 10 times more traffic from [Google][] than from
   655      [Yahoo][] or [MSN][].
   656  
   657        [google]: http://google.com/        "Google"
   658        [yahoo]:  http://search.yahoo.com/  "Yahoo Search"
   659        [msn]:    http://search.msn.com/    "MSN Search"
   660  
   661  Both of the above examples will produce the following HTML output:
   662  
   663      <p>I get 10 times more traffic from <a href="http://google.com/"
   664      title="Google">Google</a> than from
   665      <a href="http://search.yahoo.com/" title="Yahoo Search">Yahoo</a>
   666      or <a href="http://search.msn.com/" title="MSN Search">MSN</a>.</p>
   667  
   668  For comparison, here is the same paragraph written using
   669  Markdown's inline link style:
   670  
   671      I get 10 times more traffic from [Google](http://google.com/ "Google")
   672      than from [Yahoo](http://search.yahoo.com/ "Yahoo Search") or
   673      [MSN](http://search.msn.com/ "MSN Search").
   674  
   675  The point of reference-style links is not that they're easier to
   676  write. The point is that with reference-style links, your document
   677  source is vastly more readable. Compare the above examples: using
   678  reference-style links, the paragraph itself is only 81 characters
   679  long; with inline-style links, it's 176 characters; and as raw HTML,
   680  it's 234 characters. In the raw HTML, there's more markup than there
   681  is text.
   682  
   683  With Markdown's reference-style links, a source document much more
   684  closely resembles the final output, as rendered in a browser. By
   685  allowing you to move the markup-related metadata out of the paragraph,
   686  you can add links without interrupting the narrative flow of your
   687  prose.
   688  
   689  
   690  <h3 id="em">Emphasis</h3>
   691  
   692  Markdown treats asterisks (`*`) and underscores (`_`) as indicators of
   693  emphasis. Text wrapped with one `*` or `_` will be wrapped with an
   694  HTML `<em>` tag; double `*`'s or `_`'s will be wrapped with an HTML
   695  `<strong>` tag. E.g., this input:
   696  
   697      *single asterisks*
   698  
   699      _single underscores_
   700  
   701      **double asterisks**
   702  
   703      __double underscores__
   704  
   705  will produce:
   706  
   707      <em>single asterisks</em>
   708  
   709      <em>single underscores</em>
   710  
   711      <strong>double asterisks</strong>
   712  
   713      <strong>double underscores</strong>
   714  
   715  You can use whichever style you prefer; the lone restriction is that
   716  the same character must be used to open and close an emphasis span.
   717  
   718  Emphasis can be used in the middle of a word:
   719  
   720      un*fucking*believable
   721  
   722  But if you surround an `*` or `_` with spaces, it'll be treated as a
   723  literal asterisk or underscore.
   724  
   725  To produce a literal asterisk or underscore at a position where it
   726  would otherwise be used as an emphasis delimiter, you can backslash
   727  escape it:
   728  
   729      \*this text is surrounded by literal asterisks\*
   730  
   731  
   732  
   733  <h3 id="code">Code</h3>
   734  
   735  To indicate a span of code, wrap it with backtick quotes (`` ` ``).
   736  Unlike a pre-formatted code block, a code span indicates code within a
   737  normal paragraph. For example:
   738  
   739      Use the `printf()` function.
   740  
   741  will produce:
   742  
   743      <p>Use the <code>printf()</code> function.</p>
   744  
   745  To include a literal backtick character within a code span, you can use
   746  multiple backticks as the opening and closing delimiters:
   747  
   748      ``There is a literal backtick (`) here.``
   749  
   750  which will produce this:
   751  
   752      <p><code>There is a literal backtick (`) here.</code></p>
   753  
   754  The backtick delimiters surrounding a code span may include spaces --
   755  one after the opening, one before the closing. This allows you to place
   756  literal backtick characters at the beginning or end of a code span:
   757  
   758  	A single backtick in a code span: `` ` ``
   759  	
   760  	A backtick-delimited string in a code span: `` `foo` ``
   761  
   762  will produce:
   763  
   764  	<p>A single backtick in a code span: <code>`</code></p>
   765  	
   766  	<p>A backtick-delimited string in a code span: <code>`foo`</code></p>
   767  
   768  With a code span, ampersands and angle brackets are encoded as HTML
   769  entities automatically, which makes it easy to include example HTML
   770  tags. Markdown will turn this:
   771  
   772      Please don't use any `<blink>` tags.
   773  
   774  into:
   775  
   776      <p>Please don't use any <code>&lt;blink&gt;</code> tags.</p>
   777  
   778  You can write this:
   779  
   780      `&#8212;` is the decimal-encoded equivalent of `&mdash;`.
   781  
   782  to produce:
   783  
   784      <p><code>&amp;#8212;</code> is the decimal-encoded
   785      equivalent of <code>&amp;mdash;</code>.</p>
   786  
   787  
   788  
   789  <h3 id="img">Images</h3>
   790  
   791  Admittedly, it's fairly difficult to devise a "natural" syntax for
   792  placing images into a plain text document format.
   793  
   794  Markdown uses an image syntax that is intended to resemble the syntax
   795  for links, allowing for two styles: *inline* and *reference*.
   796  
   797  Inline image syntax looks like this:
   798  
   799      ![Alt text](/path/to/img.jpg)
   800  
   801      ![Alt text](/path/to/img.jpg "Optional title")
   802  
   803  That is:
   804  
   805  *   An exclamation mark: `!`;
   806  *   followed by a set of square brackets, containing the `alt`
   807      attribute text for the image;
   808  *   followed by a set of parentheses, containing the URL or path to
   809      the image, and an optional `title` attribute enclosed in double
   810      or single quotes.
   811  
   812  Reference-style image syntax looks like this:
   813  
   814      ![Alt text][id]
   815  
   816  Where "id" is the name of a defined image reference. Image references
   817  are defined using syntax identical to link references:
   818  
   819      [id]: url/to/image  "Optional title attribute"
   820  
   821  As of this writing, Markdown has no syntax for specifying the
   822  dimensions of an image; if this is important to you, you can simply
   823  use regular HTML `<img>` tags.
   824  
   825  
   826  * * *
   827  
   828  
   829  <h2 id="misc">Miscellaneous</h2>
   830  
   831  <h3 id="autolink">Automatic Links</h3>
   832  
   833  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:
   834  
   835      <http://example.com/>
   836      
   837  Markdown will turn this into:
   838  
   839      <a href="http://example.com/">http://example.com/</a>
   840  
   841  Automatic links for email addresses work similarly, except that
   842  Markdown will also perform a bit of randomized decimal and hex
   843  entity-encoding to help obscure your address from address-harvesting
   844  spambots. For example, Markdown will turn this:
   845  
   846      <address@example.com>
   847  
   848  into something like this:
   849  
   850      <a href="&#x6D;&#x61;i&#x6C;&#x74;&#x6F;:&#x61;&#x64;&#x64;&#x72;&#x65;
   851      &#115;&#115;&#64;&#101;&#120;&#x61;&#109;&#x70;&#x6C;e&#x2E;&#99;&#111;
   852      &#109;">&#x61;&#x64;&#x64;&#x72;&#x65;&#115;&#115;&#64;&#101;&#120;&#x61;
   853      &#109;&#x70;&#x6C;e&#x2E;&#99;&#111;&#109;</a>
   854  
   855  which will render in a browser as a clickable link to "address@example.com".
   856  
   857  (This sort of entity-encoding trick will indeed fool many, if not
   858  most, address-harvesting bots, but it definitely won't fool all of
   859  them. It's better than nothing, but an address published in this way
   860  will probably eventually start receiving spam.)
   861  
   862  
   863  
   864  <h3 id="backslash">Backslash Escapes</h3>
   865  
   866  Markdown allows you to use backslash escapes to generate literal
   867  characters which would otherwise have special meaning in Markdown's
   868  formatting syntax. For example, if you wanted to surround a word with
   869  literal asterisks (instead of an HTML `<em>` tag), you can backslashes
   870  before the asterisks, like this:
   871  
   872      \*literal asterisks\*
   873  
   874  Markdown provides backslash escapes for the following characters:
   875  
   876      \   backslash
   877      `   backtick
   878      *   asterisk
   879      _   underscore
   880      {}  curly braces
   881      []  square brackets
   882      ()  parentheses
   883      #   hash mark
   884  	+	plus sign
   885  	-	minus sign (hyphen)
   886      .   dot
   887      !   exclamation mark
   888