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apache-site... No thirty. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@81322 13f79535-47bb-0310-9956-ffa450edef68
94 lines
3.7 KiB
Plaintext
94 lines
3.7 KiB
Plaintext
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML><HEAD>
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<TITLE>PATH_INFO Changes in the CGI Environment</TITLE>
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</HEAD>
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<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
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<BODY
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#000080"
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ALINK="#FF0000"
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>
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<!--#include virtual="header.html" -->
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<H1 ALIGN="CENTER">PATH_INFO Changes in the CGI Environment</H1>
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<HR>
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<H2><A NAME="over">Overview</A></H2>
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<P>As implemented in Apache 1.1.1 and earlier versions, the method
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Apache used to create PATH_INFO in the CGI environment was
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counterintuitive, and could result in crashes in certain cases. In
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Apache 1.2 and beyond, this behavior has changed. Although this
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results in some compatibility problems with certain legacy CGI
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applications, the Apache 1.2 behavior is still compatible with the
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CGI/1.1 specification, and CGI scripts can be easily modified (<A
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HREF="#compat">see below</A>).
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<H2><A NAME="prob">The Problem</A></H2>
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<P>Apache 1.1.1 and earlier implemented the PATH_INFO and SCRIPT_NAME
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environment variables by looking at the filename, not the URL. While
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this resulted in the correct values in many cases, when the filesystem
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path was overloaded to contain path information, it could result in
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errant behavior. For example, if the following appeared in a config
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file:
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<PRE>
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Alias /cgi-ralph /usr/local/httpd/cgi-bin/user.cgi/ralph
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</PRE>
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<P>In this case, <CODE>user.cgi</CODE> is the CGI script, the "/ralph"
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is information to be passed onto the CGI. If this configuration was in
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place, and a request came for "<CODE>/cgi-ralph/script/</CODE>", the
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code would set PATH_INFO to "<CODE>/ralph/script</CODE>", and
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SCRIPT_NAME to "<CODE>/cgi-</CODE>". Obviously, the latter is
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incorrect. In certain cases, this could even cause the server to
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crash.</P>
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<H2><A NAME="solution">The Solution</A></H2>
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<P>Apache 1.2 and later now determine SCRIPT_NAME and PATH_INFO by
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looking directly at the URL, and determining how much of the URL is
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client-modifiable, and setting PATH_INFO to it. To use the above
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example, PATH_INFO would be set to "<CODE>/script</CODE>", and
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SCRIPT_NAME to "<CODE>/cgi-ralph</CODE>". This makes sense and results
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in no server behavior problems. It also permits the script to be
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guaranteed that
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"<CODE>http://$SERVER_NAME:$SERVER_PORT$SCRIPT_NAME$PATH_INFO</CODE>"
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will always be an accessible URL that points to the current script,
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something which was not necessarily true with previous versions of
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Apache.
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<P>However, the "<CODE>/ralph</CODE>"
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information from the <CODE>Alias</CODE> directive is lost. This is
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unfortunate, but we feel that using the filesystem to pass along this
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sort of information is not a recommended method, and a script making
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use of it "deserves" not to work. Apache 1.2b3 and later, however, do
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provide <A HREF="#compat">a workaround.</A>
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<H2><A NAME="compat">Compatibility with Previous Servers</A></H2>
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<P>It may be necessary for a script that was designed for earlier
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versions of Apache or other servers to need the information that the
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old PATH_INFO variable provided. For this purpose, Apache 1.2 (1.2b3
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and later) sets an additional variable, FILEPATH_INFO. This
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environment variable contains the value that PATH_INFO would have had
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with Apache 1.1.1.</P>
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<P>A script that wishes to work with both Apache 1.2 and earlier
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versions can simply test for the existence of FILEPATH_INFO, and use
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it if available. Otherwise, it can use PATH_INFO. For example, in
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Perl, one might use:
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<PRE>
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$path_info = $ENV{'FILEPATH_INFO'} || $ENV{'PATH_INFO'};
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</PRE>
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<P>By doing this, a script can work with all servers supporting the
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CGI/1.1 specification, including all versions of Apache.</P>
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<!--#include virtual="footer.html" -->
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</BODY>
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</HTML>
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