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diff --git a/docs/manual/env.html b/docs/manual/env.html deleted file mode 100644 index f436e32819..0000000000 --- a/docs/manual/env.html +++ /dev/null @@ -1,305 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> -<HTML> -<HEAD> -<TITLE>Environment Variables in Apache</TITLE> -</HEAD> - -<!-- Background white, links blue (unvisited), navy (visited), red (active) --> -<BODY - BGCOLOR="#FFFFFF" - TEXT="#000000" - LINK="#0000FF" - VLINK="#000080" - ALINK="#FF0000" -> -<!--#include virtual="header.html" --> -<h1 align="center">Environment Variables in Apache</h1> - -<p>Many operating systems provide a facility for storage and -transmission of information called environment variables. Apache uses -environment variables in many ways to control operations and to -communicate with other programs like CGI scripts. This document -explains some of the ways to use environment variables in Apache.</p> - -<ul> -<li><a href="#setting">Setting Environment Variables</a></li> -<li><a href="#using">Using Environment Variables</a></li> -<li><a href="#special">Special Purpose Environment Variables</a></li> -<li><a href="#examples">Examples</a></li> -</ul> - -<hr> - -<h2><a name="setting">Setting Environment Variables</a></h2> - -<table border="1"> -<tr><td valign="top"> -<strong>Related Modules</strong><br><br> - -<a href="mod/mod_env.html">mod_env</a><br> -<a href="mod/mod_rewrite.html">mod_rewrite</a><br> -<a href="mod/mod_setenvif.html">mod_setenvif</a><br> -<a href="mod/mod_unique_id.html">mod_unique_id</a><br> - -</td><td valign="top"> -<strong>Related Directives</strong><br><br> - -<A HREF="mod/mod_setenvif.html#BrowserMatch">BrowserMatch</A><br> -<A HREF="mod/mod_setenvif.html#BrowserMatchNoCase">BrowserMatchNoCase</A><br> -<A HREF="mod/mod_env.html#passenv">PassEnv</A><br> -<A HREF="mod/mod_rewrite.html#RewriteRule">RewriteRule</A><br> -<A HREF="mod/mod_env.html#setenv">SetEnv</A><br> -<A HREF="mod/mod_setenvif.html#SetEnvIf">SetEnvIf</A><br> -<A HREF="mod/mod_setenvif.html#SetEnvIfNoCase">SetEnvIfNoCase</A><br> -<A HREF="mod/mod_env.html#unsetenv">UnsetEnv</A><br> -</td></tr></table> - -<h3>Basic Environment Manipulation</h3> - -<p>The most basic way to set an environment variable in Apache is -using the unconditional <code>SetEnv</code> directive. Variables -may also be passed from the environment of the shell which started -the server using the <code>PassEnv</code> directive.</p> - -<h3>Conditional Per-Request Settings</h3> - -<p>For additional flexibility, the directives provided by mod_setenvif -allow environment variables to be set on a per-request basis, -conditional on characteristics of particular requests. For example, a -variable could be set only when a specific browser (User-Agent) is -making a request, or only when a specific Referer [sic] header is -found. Even more flexibility is available through the mod_rewrite's -<code>RewriteRule</code> which uses the <code>[E=...]</code> option to -set environment variables.</p> - -<h3>Unique Identifiers</h3> - -<p>Finally, mod_unique_id sets the environment variable -<code>UNIQUE_ID</code> for each request to a value which is guaranteed -to be unique across "all" requests under very specific conditions.</p> - -<h3>Standard CGI Variables</h3> - -<p>In addition to all environment variables set within the Apache -configuration and passed from the shell, CGI scripts and SSI pages are -provided with a set of environment variables containing -meta-information about the request as required by the <a -href="misc/FAQ.html#cgi-spec">CGI specification</a>.</p> - -<h3>Some Caveats</h3> - -<ul> - -<li>It is not possible to override or change the standard CGI -variables using the environment manipulation directives.</li> - -<li>When <a href="suexec.html">suexec</a> is used to launch CGI -scripts, the environment will be cleaned down to a set of -<em>safe</em> variables before CGI scripts are launched. The list of -<em>safe</em> variables is defined at compile-time in -<code>suexec.c</code>.</li> - -<li>For portability reasons, the names of environment variables -may contain only letters, numbers, and the underscore character. -In addition, the first character may not be a number. Characters -which do not match this restriction will be replaced by an -underscore when passed to CGI scripts and SSI pages.</li> - -</ul> - - -<hr> - -<h2><a name="using">Using Environment Variables</a></h2> - -<table border=1><tr><td valign="top"> -<strong>Related Modules</strong><br><br> - -<a href="mod/mod_access.html">mod_access</a><br> -<a href="mod/mod_cgi.html">mod_cgi</a><br> -<a href="mod/mod_include.html">mod_include</a><br> -<a href="mod/mod_log_config.html">mod_log_config</a><br> -<a href="mod/mod_rewrite.html">mod_rewrite</a><br> - -</td><td valign="top"> -<strong>Related Directives</strong><br><br> - -<A HREF="mod/mod_access.html#allow">Allow</A><br> -<a href="mod/mod_log_config.html#customlog">CustomLog</a><br> -<A HREF="mod/mod_access.html#deny">Deny</A><br> -<a href="mod/mod_log_config.html#logformat">LogFormat</a><br> -<A HREF="mod/mod_rewrite.html#RewriteCond">RewriteCond</A><br> -<A HREF="mod/mod_rewrite.html#RewriteRule">RewriteRule</A><br> - -</td></tr></table> - -<h3>CGI Scripts</h3> - -<p>One of the primary uses of environment variables is to communicate -information to CGI scripts. As discussed above, the environment -passed to CGI scripts includes standard meta-information about the request -in addition to any variables set within the Apache configuration. -For more details, see the <a href="howto/cgi.html">CGI tutorial</a>. -</p> - -<h3>SSI Pages</h3> - -<p>Server-parsed (SSI) documents processed by mod_include's -<code>server-parsed</code> handler can print environment variables -using the <code>echo</code> element, and can use environment variables -in flow control elements to makes parts of a page conditional on -characteristics of a request. Apache also provides SSI pages with the -standard CGI environment variables as discussed above. For more -details, see the <a href="howto/ssi.html">SSI tutorial</a>. -</p> - -<h3>Access Control</h3> - -<p>Access to the server can be controlled based on the value of -environment variables using the <code>allow from env=</code> and -<code>deny from env=</code></a> directives. In combination with -<code>SetEnvIf</code>, this allows for flexible control of access to -the server based on characteristics of the client. For example, you -can use these directives to deny access to a particular browser -(User-Agent). -</p> - -<h3>Conditional Logging</h3> - -<p>Environment variables can be logged in the access log using the -<code>LogFormat</code> option <code>%e</code>. In addition, the -decision on whether or not to log requests can be made based on the -status of environment variables using the conditional form of the -<code>CustomLog</code> directive. In combination with -<code>SetEnvIf</code> this allows for flexible control of which -requests are logged. For example, you can choose not to log requests -for filenames ending in <code>gif</code>, or you can choose to only -log requests from clients which are outside your subnet. -</p> - -<h3>URL Rewriting</h3> - -<p>The <code>%{ENV:...}</code> form of <em>TestString</em> in the -<code>RewriteCond</code> allows mod_rewrite's rewrite engine to make -decisions conditional on environment variables. Note that the -variables accessible in mod_rewrite without the <code>ENV:</code> -prefix are not actually environment variables. Rather, they -are variables special to mod_rewrite which cannot be accessed from -other modules.</p> - -<hr> - -<H2><a name="special">Special Purpose Environment Variables</a></H2> -<P> -Interoperability problems have led to the introduction of -mechanisms to modify the way Apache behaves when talking to particular -clients. To make these mechanisms as flexible as possible, they -are invoked by defining environment variables, typically with -<A HREF="mod/mod_setenvif.html#browsermatch">BrowserMatch</A>, though -<A HREF="mod/mod_env.html#setenv">SetEnv</A> and -<A HREF="mod/mod_env.html#passenv">PassEnv</A> could also be used, for -example. -</P> - -<H2>downgrade-1.0</H2> -<P> -This forces the request to be treated as a HTTP/1.0 request even if it -was in a later dialect. -</P> - -<H2>force-no-vary</H2> -<P> -This causes any <CODE>Vary</CODE> fields to be removed from the response -header before it is sent back to the client. Some clients don't -interpret this field correctly (see the -<A HREF="misc/known_client_problems.html">known client problems</A> -page); setting this variable can work around this problem. Setting -this variable also implies <STRONG>force-response-1.0</STRONG>. -</P> - -<H2>force-response-1.0</H2> -<P> -This forces an HTTP/1.0 response when set. It was originally implemented as a -result of a problem with AOL's proxies. Some clients may not behave correctly -when given an HTTP/1.1 response, and this can be used to interoperate with -them. -</P> - -<H2>nokeepalive</H2> -<P> -This disables <A HREF="mod/core.html#keepalive">KeepAlive</A> when set. -</P> - - -<hr> - -<h2><a name="examples">Examples</a></h2> - -<h3>Changing protocol behavior with misbehaving clients</h3> - -<p>We recommend that the following lines be included in httpd.conf -to deal with known client problems.</p> - -<pre> -# -# The following directives modify normal HTTP response behavior. -# The first directive disables keepalive for Netscape 2.x and browsers that -# spoof it. There are known problems with these browser implementations. -# The second directive is for Microsoft Internet Explorer 4.0b2 -# which has a broken HTTP/1.1 implementation and does not properly -# support keepalive when it is used on 301 or 302 (redirect) responses. -# -BrowserMatch "Mozilla/2" nokeepalive -BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0 - -# -# The following directive disables HTTP/1.1 responses to browsers which -# are in violation of the HTTP/1.0 spec by not being able to grok a -# basic 1.1 response. -# -BrowserMatch "RealPlayer 4\.0" force-response-1.0 -BrowserMatch "Java/1\.0" force-response-1.0 -BrowserMatch "JDK/1\.0" force-response-1.0 -</pre> - -<h3>Do not log requests for images in the access log</h3> - -<p>This example keeps requests for images from appearing -in the access log. It can be easily modified to prevent logging -of particular directories, or to prevent logging of requests -coming from particular hosts.</p> - -<pre> - SetEnvIf Request_URI \.gif image-request - SetEnvIf Request_URI \.jpg image-request - SetEnvIf Request_URI \.png image-request - CustomLog logs/access_log env=!image-request -</pre> - -<h3>Prevent "Image Theft"</h3> - -<p>This example shows how to keep people not on your server from using -images on your server as inline-images on their pages. This is not -a recommended configuration, but it can work in limited -circumstances. We assume that all your images are in a directory -called /web/images.</p> - -<pre> - SetEnvIf Referer "^http://www.example.com/" local_referal - # Allow browsers that do not send Referer info - SetEnvIf Referer "^$" local_referal - <Directory /web/images> - Order Deny,Allow - Deny from all - Allow from env=local_referal - </Directory> -</pre> - -<p>For more information about this technique, see the ApacheToday -tutorial "<a -href="http://apachetoday.com/news_story.php3?ltsn=2000-06-14-002-01-PS">Keeping -Your Images from Adorning Other Sites</a>".</p> - -<!--#include virtual="footer.html" --> -</BODY> -</HTML> |