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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