docs/manual/cgi_path.html.en - httpd - Git at Google

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 <title>PATH_INFO Changes in the CGI Environment - Apache HTTP Server</title>
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 <p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p>
 <p class="apache">Apache HTTP Server Version 2.0</p>
 <img alt="" src="./images/feather.gif" /></div>
 <div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="./images/left.gif" /></a></div>
 <div id="path">
 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs-project/">Documentation</a> &gt; <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>PATH_INFO Changes in the CGI Environment</h1>
     <p>As implemented in Apache 1.1.1 and earlier versions, the
     method Apache used to create PATH_INFO in the CGI environment
     was counterintuitive, and could result in crashes in certain
     cases. In Apache 1.2 and beyond, this behavior has changed.
     Although this results in some compatibility problems with
     certain legacy CGI applications, the Apache 1.2 behavior is
     still compatible with the CGI/1.1 specification, and CGI
     scripts can be easily modified (<a href="#compat">see
     below</a>).</p>
   </div>
 <div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#prob">The Problem</a></li>
 <li><img alt="" src="./images/down.gif" /> <a href="#solution">The Solution</a></li>
 <li><img alt="" src="./images/down.gif" /> <a href="#compat">Compatibility with Previous Servers</a></li>
 </ul></div>
 <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
 <div class="section">
 <h2><a name="prob" id="prob">The Problem</a></h2>
     <p>Apache 1.1.1 and earlier implemented the PATH_INFO and
     SCRIPT_NAME environment variables by looking at the filename,
     not the URL. While this resulted in the correct values in many
     cases, when the filesystem path was overloaded to contain path
     information, it could result in errant behavior. For example,
     if the following appeared in a config file:</p>

     <div class="example"><p><code>
       Alias /cgi-ralph /usr/local/httpd/cgi-bin/user.cgi/ralph
     </code></p></div>

     <p>In this case, <code>user.cgi</code> is the CGI script, the
     "/ralph" is information to be passed onto the CGI. If this
     configuration was in place, and a request came for
     "<code>/cgi-ralph/script/</code>", the code would set PATH_INFO
     to "<code>/ralph/script</code>", and SCRIPT_NAME to
     "<code>/cgi-</code>". Obviously, the latter is incorrect. In
     certain cases, this could even cause the server to crash.</p>
   </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
 <div class="section">
 <h2><a name="solution" id="solution">The Solution</a></h2>
     <p>Apache 1.2 and later now determine SCRIPT_NAME and PATH_INFO
     by looking directly at the URL, and determining how much of the
     URL is client-modifiable, and setting PATH_INFO to it. To use
     the above example, PATH_INFO would be set to
     "<code>/script</code>", and SCRIPT_NAME to
     "<code>/cgi-ralph</code>". This makes sense and results in no
     server behavior problems. It also permits the script to be
     guaranteed that
     "<code>http://$SERVER_NAME:$SERVER_PORT$SCRIPT_NAME$PATH_INFO</code>"
     will always be an accessible URL that points to the current
     script, something which was not necessarily true with previous
     versions of Apache.</p>

     <p>However, the "<code>/ralph</code>" information from the
     <code>Alias</code> directive is lost. This is unfortunate, but
     we feel that using the filesystem to pass along this sort of
     information is not a recommended method, and a script making
     use of it "deserves" not to work. Apache 1.2b3 and later,
     however, do provide <a href="#compat">a workaround.</a></p>
   </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
 <div class="section">
 <h2><a name="compat" id="compat">Compatibility with Previous Servers</a></h2>


     <p>It may be necessary for a script that was designed for
     earlier versions of Apache or other servers to need the
     information that the old PATH_INFO variable provided. For this
     purpose, Apache 1.2 (1.2b3 and later) sets an additional
     variable, FILEPATH_INFO. This environment variable contains the
     value that PATH_INFO would have had with Apache 1.1.1.</p>

     <p>A script that wishes to work with both Apache 1.2 and
     earlier versions can simply test for the existence of
     FILEPATH_INFO, and use it if available. Otherwise, it can use
     PATH_INFO. For example, in Perl, one might use:</p>

     <div class="example"><p><code>
       $path_info = $ENV{'FILEPATH_INFO'} || $ENV{'PATH_INFO'};
     </code></p></div>

     <p>By doing this, a script can work with all servers supporting
     the CGI/1.1 specification, including all versions of
     Apache.</p>
   </div></div>
 <div id="footer">
 <p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p>
 <p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p></div>
 </body></html>
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	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
	This file is generated from xml source: DO NOT EDIT
	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
	-->
	<title>PATH_INFO Changes in the CGI Environment - Apache HTTP Server</title>
	<link href="./style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
	<link href="./style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
	<link href="./style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
	<link href="./images/favicon.ico" rel="shortcut icon" /></head>
	<body id="manual-page"><div id="page-header">
	<p class="menu"><a href="./mod/">Modules</a> \| <a href="./mod/directives.html">Directives</a> \| <a href="./faq/">FAQ</a> \| <a href="./glossary.html">Glossary</a> \| <a href="./sitemap.html">Sitemap</a></p>
	<p class="apache">Apache HTTP Server Version 2.0</p>
	<img alt="" src="./images/feather.gif" /></div>
	<div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div>
	<div id="path">
	<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>PATH_INFO Changes in the CGI Environment</h1>
	<p>As implemented in Apache 1.1.1 and earlier versions, the
	method Apache used to create PATH_INFO in the CGI environment
	was counterintuitive, and could result in crashes in certain
	cases. In Apache 1.2 and beyond, this behavior has changed.
	Although this results in some compatibility problems with
	certain legacy CGI applications, the Apache 1.2 behavior is
	still compatible with the CGI/1.1 specification, and CGI
	scripts can be easily modified (<a href="#compat">see
	below</a>).</p>
	</div>
	<div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#prob">The Problem</a></li>
	<li><img alt="" src="./images/down.gif" /> <a href="#solution">The Solution</a></li>
	<li><img alt="" src="./images/down.gif" /> <a href="#compat">Compatibility with Previous Servers</a></li>
	</ul></div>
	<div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
	<div class="section">
	<h2><a name="prob" id="prob">The Problem</a></h2>
	<p>Apache 1.1.1 and earlier implemented the PATH_INFO and
	SCRIPT_NAME environment variables by looking at the filename,
	not the URL. While this resulted in the correct values in many
	cases, when the filesystem path was overloaded to contain path
	information, it could result in errant behavior. For example,
	if the following appeared in a config file:</p>

	<div class="example"><p><code>
	Alias /cgi-ralph /usr/local/httpd/cgi-bin/user.cgi/ralph
	</code></p></div>

	<p>In this case, <code>user.cgi</code> is the CGI script, the
	"/ralph" is information to be passed onto the CGI. If this
	configuration was in place, and a request came for
	"<code>/cgi-ralph/script/</code>", the code would set PATH_INFO
	to "<code>/ralph/script</code>", and SCRIPT_NAME to
	"<code>/cgi-</code>". Obviously, the latter is incorrect. In
	certain cases, this could even cause the server to crash.</p>
	</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
	<div class="section">
	<h2><a name="solution" id="solution">The Solution</a></h2>
	<p>Apache 1.2 and later now determine SCRIPT_NAME and PATH_INFO
	by looking directly at the URL, and determining how much of the
	URL is client-modifiable, and setting PATH_INFO to it. To use
	the above example, PATH_INFO would be set to
	"<code>/script</code>", and SCRIPT_NAME to
	"<code>/cgi-ralph</code>". This makes sense and results in no
	server behavior problems. It also permits the script to be
	guaranteed that
	"<code>http://$SERVER_NAME:$SERVER_PORT$SCRIPT_NAME$PATH_INFO</code>"
	will always be an accessible URL that points to the current
	script, something which was not necessarily true with previous
	versions of Apache.</p>

	<p>However, the "<code>/ralph</code>" information from the
	<code>Alias</code> directive is lost. This is unfortunate, but
	we feel that using the filesystem to pass along this sort of
	information is not a recommended method, and a script making
	use of it "deserves" not to work. Apache 1.2b3 and later,
	however, do provide <a href="#compat">a workaround.</a></p>
	</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
	<div class="section">
	<h2><a name="compat" id="compat">Compatibility with Previous Servers</a></h2>


	<p>It may be necessary for a script that was designed for
	earlier versions of Apache or other servers to need the
	information that the old PATH_INFO variable provided. For this
	purpose, Apache 1.2 (1.2b3 and later) sets an additional
	variable, FILEPATH_INFO. This environment variable contains the
	value that PATH_INFO would have had with Apache 1.1.1.</p>

	<p>A script that wishes to work with both Apache 1.2 and
	earlier versions can simply test for the existence of
	FILEPATH_INFO, and use it if available. Otherwise, it can use
	PATH_INFO. For example, in Perl, one might use:</p>

	<div class="example"><p><code>
	$path_info = $ENV{'FILEPATH_INFO'} \|\| $ENV{'PATH_INFO'};
	</code></p></div>

	<p>By doing this, a script can work with all servers supporting
	the CGI/1.1 specification, including all versions of
	Apache.</p>
	</div></div>
	<div id="footer">
	<p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p>
	<p class="menu"><a href="./mod/">Modules</a> \| <a href="./mod/directives.html">Directives</a> \| <a href="./faq/">FAQ</a> \| <a href="./glossary.html">Glossary</a> \| <a href="./sitemap.html">Sitemap</a></p></div>
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