| 1 | <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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| 2 | <hr>
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| 3 |
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| 4 | <p>
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| 5 |
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| 6 | In order to pass data about the information request from the server to
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| 7 | the script, the server uses command line arguments as well as
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| 8 | environment variables. These environment variables are set when the
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| 9 | server executes the gateway program. </p><p>
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| 10 |
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| 11 | </p><hr>
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| 12 | <h2>Specification</h2>
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| 13 |
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| 14 | <p>
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| 15 | The following environment variables are not request-specific and are
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| 16 | set for all requests: </p><p>
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| 17 |
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| 18 | </p><ul>
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| 19 | <li> <code>SERVER_SOFTWARE</code> <p>
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| 20 |
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| 21 | The name and version of the information server software answering
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| 22 | the request (and running the gateway). Format: name/version </p><p>
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| 23 |
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| 24 | </p></li><li> <code>SERVER_NAME</code> <p>
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| 25 | The server's hostname, DNS alias, or IP address as it would appear
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| 26 | in self-referencing URLs. </p><p>
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| 27 |
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| 28 | </p></li><li> <code>GATEWAY_INTERFACE</code> <p>
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| 29 | The revision of the CGI specification to which this server
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| 30 | complies. Format: CGI/revision</p><p>
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| 31 |
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| 32 | </p></li></ul>
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| 33 |
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| 34 | <hr>
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| 35 |
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| 36 | The following environment variables are specific to the request being
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| 37 | fulfilled by the gateway program: <p>
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| 38 |
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| 39 | </p><ul>
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| 40 | <li> <a name="protocol"><code>SERVER_PROTOCOL</code></a> <p>
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| 41 | The name and revision of the information protcol this request came
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| 42 | in with. Format: protocol/revision </p><p>
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| 43 |
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| 44 | </p></li><li> <code>SERVER_PORT</code> <p>
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| 45 | The port number to which the request was sent. </p><p>
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| 46 |
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| 47 | </p></li><li> <code>REQUEST_METHOD</code> <p>
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| 48 | The method with which the request was made. For HTTP, this is
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| 49 | "GET", "HEAD", "POST", etc. </p><p>
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| 50 |
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| 51 | </p></li><li> <code>PATH_INFO</code> <p>
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| 52 | The extra path information, as given by the client. In other
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| 53 | words, scripts can be accessed by their virtual pathname, followed
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| 54 | by extra information at the end of this path. The extra
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| 55 | information is sent as PATH_INFO. This information should be
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| 56 | decoded by the server if it comes from a URL before it is passed
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| 57 | to the CGI script.</p><p>
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| 58 |
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| 59 | </p></li><li> <code>PATH_TRANSLATED</code> <p>
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| 60 | The server provides a translated version of PATH_INFO, which takes
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| 61 | the path and does any virtual-to-physical mapping to it. </p><p>
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| 62 |
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| 63 | </p></li><li> <code>SCRIPT_NAME</code> <p>
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| 64 | A virtual path to the script being executed, used for
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| 65 | self-referencing URLs. </p><p>
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| 66 |
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| 67 | </p></li><li> <a name="query"><code>QUERY_STRING</code></a> <p>
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| 68 | The information which follows the ? in the <a href="http://www.ncsa.uiuc.edu/demoweb/url-primer.html">URL</a>
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| 69 | which referenced this script. This is the query information. It
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| 70 | should not be decoded in any fashion. This variable should always
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| 71 | 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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| 72 |
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| 73 | </p></li><li> <code>REMOTE_HOST</code> <p>
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| 74 | The hostname making the request. If the server does not have this
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| 75 | information, it should set REMOTE_ADDR and leave this unset.</p><p>
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| 76 |
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| 77 | </p></li><li> <code>REMOTE_ADDR</code> <p>
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| 78 | The IP address of the remote host making the request. </p><p>
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| 79 |
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| 80 | </p></li><li> <code>AUTH_TYPE</code> <p>
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| 81 | If the server supports user authentication, and the script is
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| 82 | protects, this is the protocol-specific authentication method used
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| 83 | to validate the user. </p><p>
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| 84 |
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| 85 | </p></li><li> <code>REMOTE_USER</code> <p>
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| 86 | If the server supports user authentication, and the script is
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| 87 | protected, this is the username they have authenticated as. </p><p>
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| 88 | </p></li><li> <code>REMOTE_IDENT</code> <p>
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| 89 | If the HTTP server supports RFC 931 identification, then this
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| 90 | variable will be set to the remote user name retrieved from the
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| 91 | server. Usage of this variable should be limited to logging only.
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| 92 | </p><p>
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| 93 |
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| 94 | </p></li><li> <a name="ct"><code>CONTENT_TYPE</code></a> <p>
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| 95 | For queries which have attached information, such as HTTP POST and
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| 96 | PUT, this is the content type of the data. </p><p>
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| 97 |
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| 98 | </p></li><li> <a name="cl"><code>CONTENT_LENGTH</code></a> <p>
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| 99 | The length of the said content as given by the client. </p><p>
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| 100 |
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| 101 | </p></li></ul>
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| 102 |
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| 103 |
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| 104 | <a name="headers"><hr></a>
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| 105 |
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| 106 | In addition to these, the header lines received from the client, if
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| 107 | any, are placed into the environment with the prefix HTTP_ followed by
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| 108 | the header name. Any - characters in the header name are changed to _
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| 109 | characters. The server may exclude any headers which it has already
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| 110 | processed, such as Authorization, Content-type, and Content-length. If
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| 111 | necessary, the server may choose to exclude any or all of these
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| 112 | headers if including them would exceed any system environment
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| 113 | limits. <p>
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| 114 |
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| 115 | An example of this is the HTTP_ACCEPT variable which was defined in
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| 116 | CGI/1.0. Another example is the header User-Agent.</p><p>
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| 117 |
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| 118 | </p><ul>
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| 119 | <li> <code>HTTP_ACCEPT</code> <p>
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| 120 | The MIME types which the client will accept, as given by HTTP
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| 121 | headers. Other protocols may need to get this information from
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| 122 | elsewhere. Each item in this list should be separated by commas as
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| 123 | per the HTTP spec. </p><p>
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| 124 |
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| 125 | Format: type/subtype, type/subtype </p><p>
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| 126 |
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| 127 |
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| 128 | </p></li><li> <code>HTTP_USER_AGENT</code><p>
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| 129 |
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| 130 | The browser the client is using to send the request. General
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| 131 | format: <code>software/version library/version</code>.</p><p>
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| 132 |
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| 133 | </p></li></ul>
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| 134 |
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| 135 | <hr>
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| 136 | <h2>Examples</h2>
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| 137 |
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| 138 | Examples of the setting of environment variables are really much better
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| 139 | <a href="http://hoohoo.ncsa.uiuc.edu/cgi/examples.html">demonstrated</a> than explained. <p>
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| 140 |
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| 141 | </p><hr>
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| 142 |
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| 143 | <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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| 144 | interface specification</a> <p>
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| 145 |
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| 146 | CGI - Common Gateway Interface
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| 147 | </p><address><a href="http://hoohoo.ncsa.uiuc.edu/cgi/mailtocgi.html">cgi@ncsa.uiuc.edu</a></address>
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| 148 |
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| 149 | </body></html>
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