2007-02-11 14:52:07 +00:00
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<html><head><title>CGI Environment Variables</title></head><body><h1><img alt="" src="env_files/CGIlogo.gif"> CGI Environment Variables</h1>
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<hr>
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<p>
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In order to pass data about the information request from the server to
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the script, the server uses command line arguments as well as
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environment variables. These environment variables are set when the
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server executes the gateway program. </p><p>
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</p><hr>
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<h2>Specification</h2>
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<p>
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The following environment variables are not request-specific and are
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set for all requests: </p><p>
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</p><ul>
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2007-03-20 11:30:28 +00:00
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<li> <code>SERVER_SOFTWARE</code> <p>
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2007-02-11 14:52:07 +00:00
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The name and version of the information server software answering
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the request (and running the gateway). Format: name/version </p><p>
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</p></li><li> <code>SERVER_NAME</code> <p>
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The server's hostname, DNS alias, or IP address as it would appear
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in self-referencing URLs. </p><p>
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2007-03-20 11:30:28 +00:00
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</p></li><li> <code>GATEWAY_INTERFACE</code> <p>
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The revision of the CGI specification to which this server
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complies. Format: CGI/revision</p><p>
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</p></li></ul>
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<hr>
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The following environment variables are specific to the request being
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fulfilled by the gateway program: <p>
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</p><ul>
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<li> <a name="protocol"><code>SERVER_PROTOCOL</code></a> <p>
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The name and revision of the information protcol this request came
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in with. Format: protocol/revision </p><p>
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</p></li><li> <code>SERVER_PORT</code> <p>
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The port number to which the request was sent. </p><p>
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</p></li><li> <code>REQUEST_METHOD</code> <p>
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The method with which the request was made. For HTTP, this is
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"GET", "HEAD", "POST", etc. </p><p>
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2007-03-20 11:30:28 +00:00
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</p></li><li> <code>PATH_INFO</code> <p>
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2007-02-11 14:52:07 +00:00
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The extra path information, as given by the client. In other
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words, scripts can be accessed by their virtual pathname, followed
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by extra information at the end of this path. The extra
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information is sent as PATH_INFO. This information should be
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decoded by the server if it comes from a URL before it is passed
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to the CGI script.</p><p>
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</p></li><li> <code>PATH_TRANSLATED</code> <p>
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The server provides a translated version of PATH_INFO, which takes
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the path and does any virtual-to-physical mapping to it. </p><p>
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</p></li><li> <code>SCRIPT_NAME</code> <p>
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A virtual path to the script being executed, used for
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self-referencing URLs. </p><p>
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2007-03-20 11:30:28 +00:00
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</p></li><li> <a name="query"><code>QUERY_STRING</code></a> <p>
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The information which follows the ? in the <a href="http://www.ncsa.uiuc.edu/demoweb/url-primer.html">URL</a>
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which referenced this script. This is the query information. It
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should not be decoded in any fashion. This variable should always
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be set when there is query information, regardless of <a href="http://hoohoo.ncsa.uiuc.edu/cgi/cl.html">command line decoding</a>. </p><p>
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</p></li><li> <code>REMOTE_HOST</code> <p>
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The hostname making the request. If the server does not have this
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information, it should set REMOTE_ADDR and leave this unset.</p><p>
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</p></li><li> <code>REMOTE_ADDR</code> <p>
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The IP address of the remote host making the request. </p><p>
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</p></li><li> <code>AUTH_TYPE</code> <p>
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If the server supports user authentication, and the script is
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protects, this is the protocol-specific authentication method used
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to validate the user. </p><p>
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2007-03-20 11:30:28 +00:00
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</p></li><li> <code>REMOTE_USER</code> <p>
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If the server supports user authentication, and the script is
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protected, this is the username they have authenticated as. </p><p>
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</p></li><li> <code>REMOTE_IDENT</code> <p>
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If the HTTP server supports RFC 931 identification, then this
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variable will be set to the remote user name retrieved from the
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server. Usage of this variable should be limited to logging only.
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</p><p>
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</p></li><li> <a name="ct"><code>CONTENT_TYPE</code></a> <p>
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For queries which have attached information, such as HTTP POST and
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PUT, this is the content type of the data. </p><p>
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</p></li><li> <a name="cl"><code>CONTENT_LENGTH</code></a> <p>
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The length of the said content as given by the client. </p><p>
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</p></li></ul>
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<a name="headers"><hr></a>
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In addition to these, the header lines received from the client, if
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any, are placed into the environment with the prefix HTTP_ followed by
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the header name. Any - characters in the header name are changed to _
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characters. The server may exclude any headers which it has already
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processed, such as Authorization, Content-type, and Content-length. If
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necessary, the server may choose to exclude any or all of these
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headers if including them would exceed any system environment
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limits. <p>
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An example of this is the HTTP_ACCEPT variable which was defined in
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CGI/1.0. Another example is the header User-Agent.</p><p>
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</p><ul>
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<li> <code>HTTP_ACCEPT</code> <p>
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The MIME types which the client will accept, as given by HTTP
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headers. Other protocols may need to get this information from
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elsewhere. Each item in this list should be separated by commas as
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per the HTTP spec. </p><p>
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Format: type/subtype, type/subtype </p><p>
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</p></li><li> <code>HTTP_USER_AGENT</code><p>
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The browser the client is using to send the request. General
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format: <code>software/version library/version</code>.</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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Examples of the setting of environment variables are really much better
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<a href="http://hoohoo.ncsa.uiuc.edu/cgi/examples.html">demonstrated</a> than explained. <p>
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</p><hr>
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<a href="http://hoohoo.ncsa.uiuc.edu/cgi/interface.html"><img alt="[Back]" src="env_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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