busybox/docs/cgi/env.html
<<
>>
Prefs
   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 protocol 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