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126 lines
4.4 KiB
HTML
126 lines
4.4 KiB
HTML
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<html><head><title>CGI Script output</title></head><body><h1><img alt="" src="out_files/CGIlogo.gif"> CGI Script Output</h1>
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<hr>
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<h2>Script output</h2>
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The script sends its output to stdout. This output can either be a
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document generated by the script, or instructions to the server for
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retrieving the desired output. <p>
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</p><hr>
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<h2>Script naming conventions</h2>
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Normally, scripts produce output which is interpreted and sent back to
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the client. An advantage of this is that the scripts do not need to
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send a full HTTP/1.0 header for every request. <p>
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<a name="nph">
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Some scripts may want to avoid the extra overhead of the server
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parsing their output, and talk directly to the client. In order to
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distinguish these scripts from the other scripts, CGI requires that
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the script name begins with nph- if a script does not want the server
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to parse its header. In this case, it is the script's responsibility
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to return a valid HTTP/1.0 (or HTTP/0.9) response to the client. </a></p><p>
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</p><hr>
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<h2><a name="nph">Parsed headers</a></h2>
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<a name="nph">The output of scripts begins with a small header. This header consists
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of text lines, in the same format as an </a><a href="http://www.w3.org/hypertext/WWW/Protocols/HTTP/Object_Headers.html">
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HTTP header</a>, terminated by a blank line (a line with only a
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linefeed or CR/LF). <p>
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Any headers which are not server directives are sent directly back to
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the client. Currently, this specification defines three server
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directives:</p><p>
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</p><ul>
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<li> <code>Content-type</code> <p>
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This is the MIME type of the document you are returning. </p><p>
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</p></li><li> <code>Location</code> <p>
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This is used to specify to the server that you are returning a
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reference to a document rather than an actual document. </p><p>
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If the argument to this is a URL, the server will issue a redirect
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to the client. </p><p>
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If the argument to this is a virtual path, the server will
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retrieve the document specified as if the client had requested
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that document originally. ? directives will work in here, but #
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directives must be redirected back to the client.</p><p>
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</p></li><li> <a name="status"><code>Status</code></a><p>
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This is used to give the server an HTTP/1.0 <a href="http://www.w3.org/hypertext/WWW/Protocols/HTTP/HTRESP.html">status
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line</a> to send to the client. The format is <code>nnn xxxxx</code>,
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where <code>nnn</code> is the 3-digit status code, and
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<code>xxxxx</code> is the reason string, such as "Forbidden".</p><p>
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</p></li></ul>
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<hr>
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<h2>Examples</h2>
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Let's say I have a fromgratz to HTML converter. When my converter is
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finished with its work, it will output the following on stdout (note
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that the lines beginning and ending with --- are just for illustration
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and would not be output): <p>
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</p><pre>--- start of output ---
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Content-type: text/html
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--- end of output ---
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</pre>
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Note the blank line after Content-type. <p>
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Now, let's say I have a script which, in certain instances, wants to
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return the document <code>/path/doc.txt</code> from this server just
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as if the user had actually requested
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<code>http://server:port/path/doc.txt</code> to begin with. In this
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case, the script would output: </p><p>
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</p><pre>--- start of output ---
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Location: /path/doc.txt
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--- end of output ---
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</pre>
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The server would then perform the request and send it to the client.
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<p>
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Let's say that I have a script which wants to reference our gopher
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server. In this case, if the script wanted to refer the user to
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<code>gopher://gopher.ncsa.uiuc.edu/</code>, it would output: </p><p>
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</p><pre>--- start of output ---
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Location: gopher://gopher.ncsa.uiuc.edu/
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--- end of output ---
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</pre>
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Finally, I have a script which wants to talk to the client directly.
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In this case, if the script is referenced with <a href="http://hoohoo.ncsa.uiuc.edu/cgi/env.html#protocol"><code>SERVER_PROTOCOL</code></a> of HTTP/1.0,
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the script would output the following HTTP/1.0 response: <p>
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</p><pre>--- start of output ---
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HTTP/1.0 200 OK
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Server: NCSA/1.0a6
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Content-type: text/plain
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This is a plaintext document generated on the fly just for you.
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--- end of output ---
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</pre>
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<hr>
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<a href="http://hoohoo.ncsa.uiuc.edu/cgi/interface.html"><img alt="[Back]" src="out_files/back.gif">Return to the
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interface specification</a> <p>
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CGI - Common Gateway Interface
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</p><address><a href="http://hoohoo.ncsa.uiuc.edu/cgi/mailtocgi.html">cgi@ncsa.uiuc.edu</a></address>
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</body></html>
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