318 lines
9.7 KiB
HTML
318 lines
9.7 KiB
HTML
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<title>File: SPEC</title>
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// ]]>
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</head>
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<body>
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<div id="fileHeader">
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<h1>SPEC</h1>
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<table class="header-table">
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<tr class="top-aligned-row">
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<td><strong>Path:</strong></td>
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<td>SPEC
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</td>
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</tr>
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<tr class="top-aligned-row">
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<td><strong>Last Update:</strong></td>
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<td>Fri Jan 09 17:40:06 +0100 2009</td>
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</tr>
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</table>
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</div>
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<!-- banner header -->
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<div id="bodyContent">
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<div id="contextContent">
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<div id="description">
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<p>
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This specification aims to formalize the <a
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href="../classes/Rack.html">Rack</a> protocol. You can (and should) use <a
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href="../classes/Rack/Lint.html">Rack::Lint</a> to enforce it. When you
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develop middleware, be sure to add a Lint before and after to catch all
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mistakes.
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</p>
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<h1><a href="../classes/Rack.html">Rack</a> applications</h1>
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<p>
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A <a href="../classes/Rack.html">Rack</a> application is an Ruby object
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(not a class) that responds to <tt>call</tt>. It takes exactly one
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argument, the <b>environment</b> and returns an Array of exactly three
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values: The <b>status</b>, the <b>headers</b>, and the <b>body</b>.
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</p>
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<h2>The Environment</h2>
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<p>
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The environment must be an true instance of Hash (no subclassing allowed)
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that includes CGI-like headers. The application is free to modify the
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environment. The environment is required to include these variables
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(adopted from PEP333), except when they‘d be empty, but see below.
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</p>
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<table>
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<tr><td valign="top"><tt>REQUEST_METHOD</tt>:</td><td>The HTTP request method, such as "GET" or "POST". This
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cannot ever be an empty string, and so is always required.
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</td></tr>
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<tr><td valign="top"><tt>SCRIPT_NAME</tt>:</td><td>The initial portion of the request URL‘s "path" that
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corresponds to the application object, so that the application knows its
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virtual "location". This may be an empty string, if the
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application corresponds to the "root" of the server.
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</td></tr>
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<tr><td valign="top"><tt>PATH_INFO</tt>:</td><td>The remainder of the request URL‘s "path", designating the
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virtual "location" of the request‘s target within the
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application. This may be an empty string, if the request URL targets the
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application root and does not have a trailing slash.
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</td></tr>
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<tr><td valign="top"><tt>QUERY_STRING</tt>:</td><td>The portion of the request URL that follows the <tt>?</tt>, if any. May be
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empty, but is always required!
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</td></tr>
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<tr><td valign="top"><tt>SERVER_NAME</tt>, <tt>SERVER_PORT</tt>:</td><td>When combined with <tt>SCRIPT_NAME</tt> and <tt>PATH_INFO</tt>, these
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variables can be used to complete the URL. Note, however, that
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<tt>HTTP_HOST</tt>, if present, should be used in preference to
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<tt>SERVER_NAME</tt> for reconstructing the request URL.
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<tt>SERVER_NAME</tt> and <tt>SERVER_PORT</tt> can never be empty strings,
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and so are always required.
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</td></tr>
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<tr><td valign="top"><tt>HTTP_</tt> Variables:</td><td>Variables corresponding to the client-supplied HTTP request headers (i.e.,
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variables whose names begin with <tt>HTTP_</tt>). The presence or absence
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of these variables should correspond with the presence or absence of the
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appropriate HTTP header in the request.
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</td></tr>
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</table>
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<p>
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In addition to this, the <a href="../classes/Rack.html">Rack</a>
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environment must include these <a
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href="../classes/Rack.html">Rack</a>-specific variables:
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</p>
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<table>
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<tr><td valign="top"><tt>rack.version</tt>:</td><td>The Array [0,1], representing this version of <a
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href="../classes/Rack.html">Rack</a>.
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</td></tr>
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<tr><td valign="top"><tt>rack.url_scheme</tt>:</td><td><tt>http</tt> or <tt>https</tt>, depending on the request URL.
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</td></tr>
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<tr><td valign="top"><tt>rack.input</tt>:</td><td>See below, the input stream.
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</td></tr>
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<tr><td valign="top"><tt>rack.errors</tt>:</td><td>See below, the error stream.
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</td></tr>
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<tr><td valign="top"><tt>rack.multithread</tt>:</td><td>true if the application object may be simultaneously invoked by another
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thread in the same process, false otherwise.
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</td></tr>
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<tr><td valign="top"><tt>rack.multiprocess</tt>:</td><td>true if an equivalent application object may be simultaneously invoked by
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another process, false otherwise.
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</td></tr>
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<tr><td valign="top"><tt>rack.run_once</tt>:</td><td>true if the server expects (but does not guarantee!) that the application
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will only be invoked this one time during the life of its containing
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process. Normally, this will only be true for a server based on CGI (or
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something similar).
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</td></tr>
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</table>
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<p>
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The server or the application can store their own data in the environment,
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too. The keys must contain at least one dot, and should be prefixed
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uniquely. The prefix <tt>rack.</tt> is reserved for use with the <a
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href="../classes/Rack.html">Rack</a> core distribution and must not be used
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otherwise. The environment must not contain the keys
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<tt>HTTP_CONTENT_TYPE</tt> or <tt>HTTP_CONTENT_LENGTH</tt> (use the
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versions without <tt>HTTP_</tt>). The CGI keys (named without a period)
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must have String values. There are the following restrictions:
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</p>
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<ul>
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<li><tt>rack.version</tt> must be an array of Integers.
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</li>
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<li><tt>rack.url_scheme</tt> must either be <tt>http</tt> or <tt>https</tt>.
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</li>
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<li>There must be a valid input stream in <tt>rack.input</tt>.
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</li>
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<li>There must be a valid error stream in <tt>rack.errors</tt>.
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</li>
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<li>The <tt>REQUEST_METHOD</tt> must be a valid token.
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</li>
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<li>The <tt>SCRIPT_NAME</tt>, if non-empty, must start with <tt>/</tt>
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</li>
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<li>The <tt>PATH_INFO</tt>, if non-empty, must start with <tt>/</tt>
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</li>
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<li>The <tt>CONTENT_LENGTH</tt>, if given, must consist of digits only.
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</li>
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<li>One of <tt>SCRIPT_NAME</tt> or <tt>PATH_INFO</tt> must be set.
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<tt>PATH_INFO</tt> should be <tt>/</tt> if <tt>SCRIPT_NAME</tt> is empty.
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<tt>SCRIPT_NAME</tt> never should be <tt>/</tt>, but instead be empty.
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</li>
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</ul>
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<h3>The Input Stream</h3>
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<p>
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The input stream must respond to <tt>gets</tt>, <tt>each</tt> and
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<tt>read</tt>.
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</p>
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<ul>
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<li><tt>gets</tt> must be called without arguments and return a string, or
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<tt>nil</tt> on EOF.
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</li>
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<li><tt>read</tt> must be called without or with one integer argument and
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return a string, or <tt>nil</tt> on EOF.
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</li>
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<li><tt>each</tt> must be called without arguments and only yield Strings.
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</li>
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<li><tt>close</tt> must never be called on the input stream.
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</li>
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</ul>
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<h3>The Error Stream</h3>
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<p>
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The error stream must respond to <tt>puts</tt>, <tt>write</tt> and
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<tt>flush</tt>.
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</p>
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<ul>
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<li><tt>puts</tt> must be called with a single argument that responds to
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<tt>to_s</tt>.
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</li>
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<li><tt>write</tt> must be called with a single argument that is a String.
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</li>
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<li><tt>flush</tt> must be called without arguments and must be called in order
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to make the error appear for sure.
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</li>
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<li><tt>close</tt> must never be called on the error stream.
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</li>
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</ul>
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<h2>The Response</h2>
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<h3>The Status</h3>
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<p>
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The status, if parsed as integer (<tt>to_i</tt>), must be greater than or
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equal to 100.
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</p>
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<h3>The Headers</h3>
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<p>
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The header must respond to each, and yield values of key and value. The
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header keys must be Strings. The header must not contain a <tt>Status</tt>
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key, contain keys with <tt>:</tt> or newlines in their name, contain keys
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names that end in <tt>-</tt> or <tt>_</tt>, but only contain keys that
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consist of letters, digits, <tt>_</tt> or <tt>-</tt> and start with a
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letter. The values of the header must respond to each. The values passed on
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each must be Strings and not contain characters below 037.
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</p>
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<h3>The Content-Type</h3>
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<p>
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There must be a <tt>Content-Type</tt>, except when the <tt>Status</tt> is
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1xx, 204 or 304, in which case there must be none given.
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</p>
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<h3>The Content-Length</h3>
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<p>
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There must be a <tt>Content-Length</tt>, except when the <tt>Status</tt> is
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1xx, 204 or 304, in which case there must be none given.
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</p>
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<h3>The Body</h3>
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<p>
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The Body must respond to each and must only yield String values. If the
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Body responds to close, it will be called after iteration. The Body
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commonly is an Array of Strings, the application instance itself, or a
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File-like object.
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</p>
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<h2>Thanks</h2>
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<p>
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Some parts of this specification are adopted from PEP333: Python Web Server
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Gateway Interface v1.0 (<a
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href="http://www.python.org/dev/peps/pep-0333">www.python.org/dev/peps/pep-0333</a>/).
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I‘d like to thank everyone involved in that effort.
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</p>
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</div>
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</div>
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<div id="validator-badges">
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<p><small><a href="http://validator.w3.org/check/referer">[Validate]</a></small></p>
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</html> |