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| author | (no author) <(no author)@unknown> | 2002-03-18 03:09:33 +0000 |
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| committer | (no author) <(no author)@unknown> | 2002-03-18 03:09:33 +0000 |
| commit | fc08fc78d7beb04687e3d4929207b31e1705c6e8 (patch) | |
| tree | 50626f671b637981b07f222b7f8a2d3057b267c3 /docs/manual/howto/cgi.html.en | |
| parent | 9e3a1fcd41146a0fbaf6f572a3a2502383b29f19 (diff) | |
| download | httpd-CHANGES.tar.gz | |
This commit was manufactured by cvs2svn to create tag 'CHANGES'.CHANGES
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/tags/CHANGES@93990 13f79535-47bb-0310-9956-ffa450edef68
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diff --git a/docs/manual/howto/cgi.html.en b/docs/manual/howto/cgi.html.en deleted file mode 100644 index 8d80d532d5..0000000000 --- a/docs/manual/howto/cgi.html.en +++ /dev/null @@ -1,552 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" - "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> - -<html xmlns="http://www.w3.org/1999/xhtml"> - <head> - <meta name="generator" content="HTML Tidy, see www.w3.org" /> - - <title>Apache Tutorial: Dynamic Content with CGI</title> - <link rev="made" href="mailto:rbowen@rcbowen.com" /> - </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">Dynamic Content with CGI</h1> - <a id="__index__" name="__index__"></a> <!-- INDEX BEGIN --> - - - <ul> - <li><a href="#dynamiccontentwithcgi">Dynamic Content with - CGI</a></li> - - <li> - <a href="#configuringapachetopermitcgi">Configuring Apache - to permit CGI</a> - - <ul> - <li><a href="#scriptalias">ScriptAlias</a></li> - - <li> - <a href="#cgioutsideofscriptaliasdirectories">CGI - outside of ScriptAlias directories</a> - - <ul> - <li><a - href="#explicitlyusingoptionstopermitcgiexecution">Explicitly - using Options to permit CGI execution</a></li> - - <li><a href="#htaccessfiles">.htaccess files</a></li> - </ul> - </li> - </ul> - </li> - - <li> - <a href="#writingacgiprogram">Writing a CGI program</a> - - <ul> - <li><a href="#yourfirstcgiprogram">Your first CGI - program</a></li> - </ul> - </li> - - <li> - <a href="#butitsstillnotworking">But it's still not - working!</a> - - <ul> - <li><a href="#filepermissions">File permissions</a></li> - - <li><a href="#pathinformation">Path information</a></li> - - <li><a href="#syntaxerrors">Syntax errors</a></li> - - <li><a href="#errorlogs">Error logs</a></li> - </ul> - </li> - - <li> - <a href="#whatsgoingonbehindthescenes">What's going on - behind the scenes?</a> - - <ul> - <li><a href="#environmentvariables">Environment - variables</a></li> - - <li><a href="#stdinandstdout">STDIN and STDOUT</a></li> - </ul> - </li> - - <li><a href="#cgimoduleslibraries">CGI - modules/libraries</a></li> - - <li><a href="#formoreinformation">For more - information</a></li> - </ul> - <!-- INDEX END --> - <hr /> - - <h2><a id="dynamiccontentwithcgi" - name="dynamiccontentwithcgi">Dynamic Content with CGI</a></h2> - - <table border="1"> - <tr> - <td valign="top"><strong>Related Modules</strong><br /> - <br /> - <a href="../mod/mod_alias.html">mod_alias</a><br /> - <a href="../mod/mod_cgi.html">mod_cgi</a><br /> - </td> - - <td valign="top"><strong>Related Directives</strong><br /> - <br /> - <a - href="../mod/mod_mime.html#addhandler">AddHandler</a><br /> - <a href="../mod/core.html#options">Options</a><br /> - <a - href="../mod/mod_alias.html#scriptalias">ScriptAlias</a><br /> - </td> - </tr> - </table> - - <p>The CGI (Common Gateway Interface) defines a way for a web - server to interact with external content-generating programs, - which are often referred to as CGI programs or CGI scripts. It - is the simplest, and most common, way to put dynamic content on - your web site. This document will be an introduction to setting - up CGI on your Apache web server, and getting started writing - CGI programs.</p> - <hr /> - - <h2><a id="configuringapachetopermitcgi" - name="configuringapachetopermitcgi">Configuring Apache to - permit CGI</a></h2> - - <p>In order to get your CGI programs to work properly, you'll - need to have Apache configured to permit CGI execution. There - are several ways to do this.</p> - - <h3><a id="scriptalias" name="scriptalias">ScriptAlias</a></h3> - - <p>The <code>ScriptAlias</code> directive tells Apache that a - particular directory is set aside for CGI programs. Apache will - assume that every file in this directory is a CGI program, and - will attempt to execute it, when that particular resource is - requested by a client.</p> - - <p>The <code>ScriptAlias</code> directive looks like:</p> -<pre> - ScriptAlias /cgi-bin/ /usr/local/apache/cgi-bin/ -</pre> - - <p>The example shown is from your default - <code>httpd.conf</code> configuration file, if you installed - Apache in the default location. The <code>ScriptAlias</code> - directive is much like the <code>Alias</code> directive, which - defines a URL prefix that is to mapped to a particular - directory. <code>Alias</code> and <code>ScriptAlias</code> are - usually used for directories that are outside of the - <code>DocumentRoot</code> directory. The difference between - <code>Alias</code> and <code>ScriptAlias</code> is that - <code>ScriptAlias</code> has the added meaning that everything - under that URL prefix will be considered a CGI program. So, the - example above tells Apache that any request for a resource - beginning with <code>/cgi-bin/</code> should be served from the - directory <code>/usr/local/apache/cgi-bin/</code>, and should - be treated as a CGI program.</p> - - <p>For example, if the URL - <code>http://dev.rcbowen.com/cgi-bin/test.pl</code> is - requested, Apache will attempt to execute the file - <code>/usr/local/apache/cgi-bin/test.pl</code> and return the - output. Of course, the file will have to exist, and be - executable, and return output in a particular way, or Apache - will return an error message.</p> - - <h3><a id="cgioutsideofscriptaliasdirectories" - name="cgioutsideofscriptaliasdirectories">CGI outside of - ScriptAlias directories</a></h3> - - <p>CGI programs are often restricted to - <code>ScriptAlias</code>'ed directories for security reasons. - In this way, administrators can tightly control who is allowed - to use CGI programs. However, if the proper security - precautions are taken, there is no reason why CGI programs - cannot be run from arbitrary directories. For example, you may - wish to let users have web content in their home directories - with the <code>UserDir</code> directive. If they want to have - their own CGI programs, but don't have access to the main - <code>cgi-bin</code> directory, they will need to be able to - run CGI programs elsewhere.</p> - - <h3><a id="explicitlyusingoptionstopermitcgiexecution" - name="explicitlyusingoptionstopermitcgiexecution">Explicitly - using Options to permit CGI execution</a></h3> - - <p>You could explicitly use the <code>Options</code> directive, - inside your main server configuration file, to specify that CGI - execution was permitted in a particular directory:</p> -<pre> - <Directory /usr/local/apache/htdocs/somedir> - Options +ExecCGI - </Directory> -</pre> - - <p>The above directive tells Apache to permit the execution of - CGI files. You will also need to tell the server what files are - CGI files. The following <code>AddHandler</code> directive - tells the server to treat all files with the <code>cgi</code> - or <code>pl</code> extension as CGI programs:</p> -<pre> - AddHandler cgi-script cgi pl -</pre> - - <h3><a id="htaccessfiles" name="htaccessfiles">.htaccess - files</a></h3> - - <p>A <code>.htaccess</code> file is a way to set configuration - directives on a per-directory basis. When Apache serves a - resource, it looks in the directory from which it is serving a - file for a file called <code>.htaccess</code>, and, if it finds - it, it will apply directives found therein. - <code>.htaccess</code> files can be permitted with the - <code>AllowOverride</code> directive, which specifies what - types of directives can appear in these files, or if they are - not allowed at all. To permit the directive we will need for - this purpose, the following configuration will be needed in - your main server configuration:</p> -<pre> - AllowOverride Options -</pre> - - <p>In the <code>.htaccess</code> file, you'll need the - following directive:</p> -<pre> - Options +ExecCGI -</pre> - - <p>which tells Apache that execution of CGI programs is - permitted in this directory.</p> - <hr /> - - <h2><a id="writingacgiprogram" - name="writingacgiprogram">Writing a CGI program</a></h2> - - <p>There are two main differences between ``regular'' - programming, and CGI programming.</p> - - <p>First, all output from your CGI program must be preceded by - a MIME-type header. This is HTTP header that tells the client - what sort of content it is receiving. Most of the time, this - will look like:</p> -<pre> - Content-type: text/html -</pre> - - <p>Secondly, your output needs to be in HTML, or some other - format that a browser will be able to display. Most of the - time, this will be HTML, but occasionally you might write a CGI - program that outputs a gif image, or other non-HTML - content.</p> - - <p>Apart from those two things, writing a CGI program will look - a lot like any other program that you might write.</p> - - <h3><a id="yourfirstcgiprogram" name="yourfirstcgiprogram">Your - first CGI program</a></h3> - - <p>The following is an example CGI program that prints one line - to your browser. Type in the following, save it to a file - called <code>first.pl</code>, and put it in your - <code>cgi-bin</code> directory.</p> -<pre> - #!/usr/bin/perl - print "Content-type: text/html\r\n\r\n"; - print "Hello, World."; -</pre> - - <p>Even if you are not familiar with Perl, you should be able - to see what is happening here. The first line tells Apache (or - whatever shell you happen to be running under) that this - program can be executed by feeding the file to the interpreter - found at the location <code>/usr/bin/perl</code>. The second - line prints the content-type declaration we talked about, - followed by two carriage-return newline pairs. This puts a - blank line after the header, to indicate the end of the HTTP - headers, and the beginning of the body. The third line prints - the string ``Hello, World.'' And that's the end of it.</p> - - <p>If you open your favorite browser and tell it to get the - address</p> -<pre> - http://www.example.com/cgi-bin/first.pl -</pre> - - <p>or wherever you put your file, you will see the one line - <code>Hello, World.</code> appear in your browser window. It's - not very exciting, but once you get that working, you'll have a - good chance of getting just about anything working.</p> - <hr /> - - <h2><a id="butitsstillnotworking" - name="butitsstillnotworking">But it's still not - working!</a></h2> - - <p>There are four basic things that you may see in your browser - when you try to access your CGI program from the web:</p> - - <dl> - <dt>The output of your CGI program</dt> - - <dd>Great! That means everything worked fine.<br /> - <br /> - </dd> - - <dt>The source code of your CGI program or a "POST Method Not - Allowed" message</dt> - - <dd>That means that you have not properly configured Apache - to process your CGI program. Reread the section on <a - href="#configuringapachetopermitcgi">configuring Apache</a> - and try to find what you missed.<br /> - <br /> - </dd> - - <dt>A message starting with "Forbidden"</dt> - - <dd>That means that there is a permissions problem. Check the - <a href="#errorlogs">Apache error log</a> and the section - below on <a href="#filepermissions">file - permissions</a>.<br /> - <br /> - </dd> - - <dt>A message saying "Internal Server Error"</dt> - - <dd>If you check the <a href="#errorlogs">Apache error - log</a>, you will probably find that it says "Premature end - of script headers", possibly along with an error message - generated by your CGI program. In this case, you will want to - check each of the below sections to see what might be - preventing your CGI program from emitting the proper HTTP - headers.</dd> - </dl> - - <h3><a id="filepermissions" name="filepermissions">File - permissions</a></h3> - - <p>Remember that the server does not run as you. That is, when - the server starts up, it is running with the permissions of an - unprivileged user - usually ``nobody'', or ``www'' - and so it - will need extra permissions to execute files that are owned by - you. Usually, the way to give a file sufficient permissions to - be executed by ``nobody'' is to give everyone execute - permission on the file:</p> -<pre> - chmod a+x first.pl -</pre> - - <p>Also, if your program reads from, or writes to, any other - files, those files will need to have the correct permissions to - permit this.</p> - - <p>The exception to this is when the server is configured to - use <a href="../suexec.html">suexec</a>. This program allows - CGI programs to be run under different user permissions, - depending on which virtual host or user home directory they are - located in. Suexec has very strict permission checking, and any - failure in that checking will result in your CGI programs - failing with an "Internal Server Error". In this case, you will - need to check the suexec log file to see what specific security - check is failing.</p> - - <h3><a id="pathinformation" name="pathinformation">Path - information</a></h3> - - <p>When you run a program from your command line, you have - certain information that is passed to the shell without you - thinking about it. For example, you have a path, which tells - the shell where it can look for files that you reference.</p> - - <p>When a program runs through the web server as a CGI program, - it does not have that path. Any programs that you invoke in - your CGI program (like 'sendmail', for example) will need to be - specified by a full path, so that the shell can find them when - it attempts to execute your CGI program.</p> - - <p>A common manifestation of this is the path to the script - interpreter (often <code>perl</code>) indicated in the first - line of your CGI program, which will look something like:</p> -<pre> - #!/usr/bin/perl -</pre> - - <p>Make sure that this is in fact the path to the - interpreter.</p> - - <h3><a id="syntaxerrors" name="syntaxerrors">Syntax - errors</a></h3> - - <p>Most of the time when a CGI program fails, it's because of a - problem with the program itself. This is particularly true once - you get the hang of this CGI stuff, and no longer make the - above two mistakes. Always attempt to run your program from the - command line before you test if via a browser. This will - eliminate most of your problems.</p> - - <h3><a id="errorlogs" name="errorlogs">Error logs</a></h3> - - <p>The error logs are your friend. Anything that goes wrong - generates message in the error log. You should always look - there first. If the place where you are hosting your web site - does not permit you access to the error log, you should - probably host your site somewhere else. Learn to read the error - logs, and you'll find that almost all of your problems are - quickly identified, and quickly solved.</p> - <hr /> - - <h2><a id="whatsgoingonbehindthescenes" - name="whatsgoingonbehindthescenes">What's going on behind the - scenes?</a></h2> - - <p>As you become more advanced in CGI programming, it will - become useful to understand more about what's happening behind - the scenes. Specifically, how the browser and server - communicate with one another. Because although it's all very - well to write a program that prints ``Hello, World.'', it's not - particularly useful.</p> - - <h3><a id="environmentvariables" - name="environmentvariables">Environment variables</a></h3> - - <p>Environment variables are values that float around you as - you use your computer. They are useful things like your path - (where the computer searches for a the actual file implementing - a command when you type it), your username, your terminal type, - and so on. For a full list of your normal, every day - environment variables, type <code>env</code> at a command - prompt.</p> - - <p>During the CGI transaction, the server and the browser also - set environment variables, so that they can communicate with - one another. These are things like the browser type (Netscape, - IE, Lynx), the server type (Apache, IIS, WebSite), the name of - the CGI program that is being run, and so on.</p> - - <p>These variables are available to the CGI programmer, and are - half of the story of the client-server communication. The - complete list of required variables is at <a - href="http://hoohoo.ncsa.uiuc.edu/cgi/env.html">http://hoohoo.ncsa.uiuc.edu/cgi/env.html</a></p> - - <p>This simple Perl CGI program will display all of the - environment variables that are being passed around. Two similar - programs are included in the <code>cgi-bin</code> directory of - the Apache distribution. Note that some variables are required, - while others are optional, so you may see some variables listed - that were not in the official list. In addition, Apache - provides many different ways for you to <a - href="../env.html">add your own environment variables</a> to - the basic ones provided by default.</p> -<pre> - #!/usr/bin/perl - print "Content-type: text/html\n\n"; - foreach $key (keys %ENV) { - print "$key --> $ENV{$key}<br>"; - } -</pre> - - <h3><a id="stdinandstdout" name="stdinandstdout">STDIN and - STDOUT</a></h3> - - <p>Other communication between the server and the client - happens over standard input (<code>STDIN</code>) and standard - output (<code>STDOUT</code>). In normal everyday context, - <code>STDIN</code> means the keyboard, or a file that a program - is given to act on, and <code>STDOUT</code> usually means the - console or screen.</p> - - <p>When you <code>POST</code> a web form to a CGI program, the - data in that form is bundled up into a special format and gets - delivered to your CGI program over <code>STDIN</code>. The - program then can process that data as though it was coming in - from the keyboard, or from a file</p> - - <p>The ``special format'' is very simple. A field name and its - value are joined together with an equals (=) sign, and pairs of - values are joined together with an ampersand (&). - Inconvenient characters like spaces, ampersands, and equals - signs, are converted into their hex equivalent so that they - don't gum up the works. The whole data string might look - something like:</p> -<pre> - name=Rich%20Bowen&city=Lexington&state=KY&sidekick=Squirrel%20Monkey -</pre> - - <p>You'll sometimes also see this type of string appended to - the a URL. When that is done, the server puts that string into - the environment variable called <code>QUERY_STRING</code>. - That's called a <code>GET</code> request. Your HTML form - specifies whether a <code>GET</code> or a <code>POST</code> is - used to deliver the data, by setting the <code>METHOD</code> - attribute in the <code>FORM</code> tag.</p> - - <p>Your program is then responsible for splitting that string - up into useful information. Fortunately, there are libraries - and modules available to help you process this data, as well as - handle other of the aspects of your CGI program.</p> - <hr /> - - <h2><a id="cgimoduleslibraries" name="cgimoduleslibraries">CGI - modules/libraries</a></h2> - - <p>When you write CGI programs, you should consider using a - code library, or module, to do most of the grunt work for you. - This leads to fewer errors, and faster development.</p> - - <p>If you're writing CGI programs in Perl, modules are - available on <a href="http://www.cpan.org/">CPAN</a>. The most - popular module for this purpose is CGI.pm. You might also - consider CGI::Lite, which implements a minimal set of - functionality, which is all you need in most programs.</p> - - <p>If you're writing CGI programs in C, there are a variety of - options. One of these is the CGIC library, from <a - href="http://www.boutell.com/cgic/">http://www.boutell.com/cgic/</a></p> - <hr /> - - <h2><a id="formoreinformation" name="formoreinformation">For - more information</a></h2> - - <p>There are a large number of CGI resources on the web. You - can discuss CGI problems with other users on the Usenet group - comp.infosystems.www.authoring.cgi. And the -servers mailing - list from the HTML Writers Guild is a great source of answers - to your questions. You can find out more at <a - href="http://www.hwg.org/lists/hwg-servers/">http://www.hwg.org/lists/hwg-servers/</a></p> - - <p>And, of course, you should probably read the CGI - specification, which has all the details on the operation of - CGI programs. You can find the original version at the <a - href="http://hoohoo.ncsa.uiuc.edu/cgi/interface.html">NCSA</a> - and there is an updated draft at the <a - href="http://web.golux.com/coar/cgi/">Common Gateway Interface - RFC project</a>.</p> - - <p>When you post a question about a CGI problem that you're - having, whether to a mailing list, or to a newsgroup, make sure - you provide enough information about what happened, what you - expected to happen, and how what actually happened was - different, what server you're running, what language your CGI - program was in, and, if possible, the offending code. This will - make finding your problem much simpler.</p> - - <p>Note that questions about CGI problems should - <strong>never</strong> be posted to the Apache bug database - unless you are sure you have found a problem in the Apache - source code.</p> - <!--#include virtual="footer.html" --> - </body> -</html> - |