1<html><head><title>CGI Environment Variables</title></head><body><h1><img alt="" src="env_files/CGIlogo.gif"> CGI Environment Variables</h1> 2<hr> 3 4<p> 5 6In order to pass data about the information request from the server to 7the script, the server uses command line arguments as well as 8environment variables. These environment variables are set when the 9server executes the gateway program. </p><p> 10 11</p><hr> 12<h2>Specification</h2> 13 14 <p> 15The following environment variables are not request-specific and are 16set for all requests: </p><p> 17 18</p><ul> 19<li> <code>SERVER_SOFTWARE</code> <p> 20 21 The name and version of the information server software answering 22 the request (and running the gateway). Format: name/version </p><p> 23 24</p></li><li> <code>SERVER_NAME</code> <p> 25 The server's hostname, DNS alias, or IP address as it would appear 26 in self-referencing URLs. </p><p> 27 28</p></li><li> <code>GATEWAY_INTERFACE</code> <p> 29 The revision of the CGI specification to which this server 30 complies. Format: CGI/revision</p><p> 31 32</p></li></ul> 33 34<hr> 35 36The following environment variables are specific to the request being 37fulfilled by the gateway program: <p> 38 39</p><ul> 40<li> <a name="protocol"><code>SERVER_PROTOCOL</code></a> <p> 41 The name and revision of the information protcol this request came 42 in with. Format: protocol/revision </p><p> 43 44</p></li><li> <code>SERVER_PORT</code> <p> 45 The port number to which the request was sent. </p><p> 46 47</p></li><li> <code>REQUEST_METHOD</code> <p> 48 The method with which the request was made. For HTTP, this is 49 "GET", "HEAD", "POST", etc. </p><p> 50 51</p></li><li> <code>PATH_INFO</code> <p> 52 The extra path information, as given by the client. In other 53 words, scripts can be accessed by their virtual pathname, followed 54 by extra information at the end of this path. The extra 55 information is sent as PATH_INFO. This information should be 56 decoded by the server if it comes from a URL before it is passed 57 to the CGI script.</p><p> 58 59</p></li><li> <code>PATH_TRANSLATED</code> <p> 60 The server provides a translated version of PATH_INFO, which takes 61 the path and does any virtual-to-physical mapping to it. </p><p> 62 63</p></li><li> <code>SCRIPT_NAME</code> <p> 64 A virtual path to the script being executed, used for 65 self-referencing URLs. </p><p> 66 67</p></li><li> <a name="query"><code>QUERY_STRING</code></a> <p> 68 The information which follows the ? in the <a href="http://www.ncsa.uiuc.edu/demoweb/url-primer.html">URL</a> 69 which referenced this script. This is the query information. It 70 should not be decoded in any fashion. This variable should always 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> 72 73</p></li><li> <code>REMOTE_HOST</code> <p> 74 The hostname making the request. If the server does not have this 75 information, it should set REMOTE_ADDR and leave this unset.</p><p> 76 77</p></li><li> <code>REMOTE_ADDR</code> <p> 78 The IP address of the remote host making the request. </p><p> 79 80</p></li><li> <code>AUTH_TYPE</code> <p> 81 If the server supports user authentication, and the script is 82 protects, this is the protocol-specific authentication method used 83 to validate the user. </p><p> 84 85</p></li><li> <code>REMOTE_USER</code> <p> 86 If the server supports user authentication, and the script is 87 protected, this is the username they have authenticated as. </p><p> 88</p></li><li> <code>REMOTE_IDENT</code> <p> 89 If the HTTP server supports RFC 931 identification, then this 90 variable will be set to the remote user name retrieved from the 91 server. Usage of this variable should be limited to logging only. 92 </p><p> 93 94</p></li><li> <a name="ct"><code>CONTENT_TYPE</code></a> <p> 95 For queries which have attached information, such as HTTP POST and 96 PUT, this is the content type of the data. </p><p> 97 98</p></li><li> <a name="cl"><code>CONTENT_LENGTH</code></a> <p> 99 The length of the said content as given by the client. </p><p> 100 101</p></li></ul> 102 103 104<a name="headers"><hr></a> 105 106In addition to these, the header lines received from the client, if 107any, are placed into the environment with the prefix HTTP_ followed by 108the header name. Any - characters in the header name are changed to _ 109characters. The server may exclude any headers which it has already 110processed, such as Authorization, Content-type, and Content-length. If 111necessary, the server may choose to exclude any or all of these 112headers if including them would exceed any system environment 113limits. <p> 114 115An example of this is the HTTP_ACCEPT variable which was defined in 116CGI/1.0. Another example is the header User-Agent.</p><p> 117 118</p><ul> 119<li> <code>HTTP_ACCEPT</code> <p> 120 The MIME types which the client will accept, as given by HTTP 121 headers. Other protocols may need to get this information from 122 elsewhere. Each item in this list should be separated by commas as 123 per the HTTP spec. </p><p> 124 125 Format: type/subtype, type/subtype </p><p> 126 127 128</p></li><li> <code>HTTP_USER_AGENT</code><p> 129 130 The browser the client is using to send the request. General 131format: <code>software/version library/version</code>.</p><p> 132 133</p></li></ul> 134 135<hr> 136<h2>Examples</h2> 137 138Examples of the setting of environment variables are really much better 139<a href="http://hoohoo.ncsa.uiuc.edu/cgi/examples.html">demonstrated</a> than explained. <p> 140 141</p><hr> 142 143<a href="http://hoohoo.ncsa.uiuc.edu/cgi/interface.html"><img alt="[Back]" src="env_files/back.gif">Return to the 144interface specification</a> <p> 145 146CGI - Common Gateway Interface 147</p><address><a href="http://hoohoo.ncsa.uiuc.edu/cgi/mailtocgi.html">cgi@ncsa.uiuc.edu</a></address> 148 149</body></html> 150
