Commit 4863d9c7 authored by Alexei Kosut's avatar Alexei Kosut
Browse files

Document the change in SCRIPT_NAME/PATH_INFO behavior, and the addition of 

FILEPATH_INFO.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@77293 13f79535-47bb-0310-9956-ffa450edef68
parent f962abe8

docs/manual/cgi_path.html

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Changes for docs/manual/cgi_path.html: 84 added lines, 0 removed lines.
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<html><head>

<title>PATH_INFO Changes in the CGI Environment</title>

</head><body>



<!--#include virtual="header.html" -->

<h1>PATH_INFO Changes in the CGI Environment</h1>



<hr>



<h2><a name="over">Overview</a></h2>



<p>As implemented in Apache 1.1.1 and earlier versions, the method

Apache used to create PATH_INFO in the CGI environment was

counterintiutive, 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>).



<h2><a name="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:

<pre>

     Alias /cgi-ralph /usr/local/httpd/cgi-bin/user.cgi/ralph

</pre>

<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>



<h2><a name="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

gauranteed that

"<code>http://$SERVER_NAME:$SERVER_PORT$SCRIPT_NAME$PATH_INFO</code>"

will always be an accessable URL that points to the current script,

something which was not neccessarily true with previous versions of

Apache.



<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>



<h2><a name="compat">Compatibility with Previous Servers</a></h2>



<p>It may be neccessary 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 existance of FILEPATH_INFO, and use

it if available. Otherwise, it can use PATH_INFO. For example, in

Perl, one might use:

<pre>

    $path_info = $ENV{'FILEPATH_INFO'} || $ENV{'PATH_INFO'};

</pre>



<p>By doing this, a script can work with all servers supporting the

CGI/1.1 specification, including all versions of Apache.</p>



<!--#include virtual="footer.html" -->

</BODY>

</HTML>

docs/manual/cgi_path.html.en

0 → 100644
+84 −0
Changes for docs/manual/cgi_path.html.en: 84 added lines, 0 removed lines.
Original line number Diff line number Diff line 
<html><head>

<title>PATH_INFO Changes in the CGI Environment</title>

</head><body>



<!--#include virtual="header.html" -->

<h1>PATH_INFO Changes in the CGI Environment</h1>



<hr>



<h2><a name="over">Overview</a></h2>



<p>As implemented in Apache 1.1.1 and earlier versions, the method

Apache used to create PATH_INFO in the CGI environment was

counterintiutive, 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>).



<h2><a name="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:

<pre>

     Alias /cgi-ralph /usr/local/httpd/cgi-bin/user.cgi/ralph

</pre>

<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>



<h2><a name="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

gauranteed that

"<code>http://$SERVER_NAME:$SERVER_PORT$SCRIPT_NAME$PATH_INFO</code>"

will always be an accessable URL that points to the current script,

something which was not neccessarily true with previous versions of

Apache.



<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>



<h2><a name="compat">Compatibility with Previous Servers</a></h2>



<p>It may be neccessary 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 existance of FILEPATH_INFO, and use

it if available. Otherwise, it can use PATH_INFO. For example, in

Perl, one might use:

<pre>

    $path_info = $ENV{'FILEPATH_INFO'} || $ENV{'PATH_INFO'};

</pre>



<p>By doing this, a script can work with all servers supporting the

CGI/1.1 specification, including all versions of Apache.</p>



<!--#include virtual="footer.html" -->

</BODY>

</HTML>