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<LI><A NAME="tex2html2668"
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<H1><A NAME="SECTION003900000000000000000">
36. <TT>
<FONT COLOR="#0000ff">httpd</FONT></TT> -- Apache Web Server</A>
</H1>

<P>
<A NAME="chap:apache"></A>
<P>
In this chapter, we will show how to set up a web
server running virtual domains
and dynamic CGI web
pages. HTML is not covered, and you are expected
to have some understanding of what HTML is, or at least where to find
documentation about it.

<P>

<H1><A NAME="SECTION003910000000000000000">
36.1 Web Server Basics</A>
</H1>

<P>
<A NAME="sec:httpdsh"></A>
<P>
In Section <A HREF="node29.html#sec:telnetcnn">26.2</A> we showed a simple HTTP session
with the <TT>
<FONT COLOR="#0000ff">telnet</FONT></TT> command.
A <I>web server</I> is really nothing
more than a program that reads a file from the hard disk whenever a
<TT>
<FONT COLOR="#0000ff">GET&nbsp;/&lt;filename&gt;.html&nbsp;HTTP/1.0</FONT></TT> request comes in
on port 80. Here, we will show a simple web server written in
shell script. <FONT COLOR="#ffa500">[Not by me. The author did not put his name in the source,
so if you are out there, please drop me an email.]</FONT> You will need to add the line

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>www&nbsp;stream&nbsp;&nbsp;tcp&nbsp;&nbsp;nowait&nbsp;&nbsp;nobody&nbsp;&nbsp;/usr/local/sbin/sh-httpd</code><br>
</FONT></TD></TR></TABLE><P>
to your <TT>
<FONT COLOR="#0000ff">/etc/inetd.conf</FONT></TT> file. If you are running
<TT>
<FONT COLOR="#0000ff">xinetd</FONT></TT>, then you will need to add a file containing

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>service&nbsp;www</code><br>
<code>{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;socket_type&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=&nbsp;stream</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;wait&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=&nbsp;no</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;user&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=&nbsp;nobody</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;server&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=&nbsp;/usr/local/sbin/sh-httpd</code><br>
<code>}</code><br>
</FONT></TD></TR></TABLE><P>
to your <TT>
<FONT COLOR="#0000ff">/etc/xinetd.d/</FONT></TT>
directory. Then, you must stop any already running web
servers and restart <TT>
<FONT COLOR="#0000ff">inetd</FONT></TT> (or
<TT>
<FONT COLOR="#0000ff">xinetd</FONT></TT>).

<P>
You will also have to create a log file
(<TT>
<FONT COLOR="#0000ff">/usr/local/var/log/sh-httpd.log</FONT></TT>) and at least
one web page (<TT>
<FONT COLOR="#0000ff">/usr/local/var/sh-www/index.html</FONT></TT>)
for your server to serve. It can contain, say:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;HTML&#062;</code><br>
<code>&nbsp;&#060;HEAD&#062;</code><br>
<code>&nbsp;&nbsp;&#060;TITLE&#062;My&nbsp;First&nbsp;Document&#060;/TITLE&#062;</code><br>
<code>&nbsp;&#060;/HEAD&#062;</code><br>
<code>&nbsp;&#060;BODY&nbsp;bgcolor=#CCCCCC&nbsp;text="#000000"&#062;</code><br>
<code>This&nbsp;is&nbsp;my&nbsp;first&nbsp;document&#060;P&#062;</code><br>
<code>Please&nbsp;visit</code><br>
<code>&nbsp;&nbsp;&#060;A&nbsp;HREF="http://rute.sourceforge.net/"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;The&nbsp;Rute&nbsp;Home&nbsp;Page</code><br>
<code>&nbsp;&nbsp;&#060;/A&#062;</code><br>
<code>for&nbsp;more&nbsp;info.&#060;/P&#062;</code><br>
<code>&nbsp;&#060;/BODY&#062;</code><br>
<code>&#060;/HTML&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Note that the server runs as <TT>
<FONT COLOR="#0000ff">nobody</FONT></TT>, so the log file must be writable
by the <TT>
<FONT COLOR="#0000ff">nobody</FONT></TT> user, and the <TT>
<FONT COLOR="#0000ff">index.html</FONT></TT> file must be readable. Also
note the use of the <TT>
<FONT COLOR="#0000ff">getpeername</FONT></TT> command, which can be changed to <TT>
<FONT COLOR="#0000ff">PEER=""</FONT></TT>
if you do not have the <TT>
<FONT COLOR="#0000ff">netpipes</FONT></TT> package installed. <FONT COLOR="#ffa500">[I am not completely
sure if other commands used here are unavailable on other U<SMALL>NIX</SMALL>
systems.]</FONT>.

<P>

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>35</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>40</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>45</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>50</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>55</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>60</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>65</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>70</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>75</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>80</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>85</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>90</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>95</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>100</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>105</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>110</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>115</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>120</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>VERSION=0.1</code><br>
<code>NAME="ShellHTTPD"</code><br>
<code>DEFCONTENT="text/html"</code><br>
<code>DOCROOT=/usr/local/var/sh-www</code><br>
<code>DEFINDEX=index.html</code><br>
<code>LOGFILE=/usr/local/var/log/sh-httpd.log</code><br>
<code>&nbsp;</code><br>
<code>log()&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;REMOTE_HOST=$1</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;REFERRER=$2</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;CODE=$3</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;SIZE=$4</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;"$REMOTE_HOST&nbsp;$REFERRER&nbsp;-&nbsp;[$REQ_DATE]&nbsp;\</code><br>
<code>\"${REQUEST}\"&nbsp;${CODE}&nbsp;${SIZE}"&nbsp;&#062;&#062;&nbsp;${LOGFILE}&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>print_header()&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"HTTP/1.0&nbsp;200&nbsp;OK\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Server:&nbsp;${NAME}/${VERSION}\r"&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Date:&nbsp;`date`\r"</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>print_error()&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"HTTP/1.0&nbsp;$1&nbsp;$2\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Content-type:&nbsp;$DEFCONTENT\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Connection:&nbsp;close\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Date:&nbsp;`date`\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"$2\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;exit&nbsp;1</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>guess_content_type()&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;FILE=$1</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;CONTENT</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;case&nbsp;${FILE##*.}&nbsp;in</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;html)&nbsp;CONTENT=$DEFCONTENT&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;gz)&nbsp;CONTENT=application/x-gzip&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*)&nbsp;CONTENT=application/octet-stream&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;esac</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Content-type:&nbsp;$CONTENT"</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>do_get()&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;DIR</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;NURL</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;LEN</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;[&nbsp;!&nbsp;-d&nbsp;$DOCROOT&nbsp;]&#059;&nbsp;then</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log&nbsp;${PEER}&nbsp;-&nbsp;404&nbsp;0</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print_error&nbsp;404&nbsp;"No&nbsp;such&nbsp;file&nbsp;or&nbsp;directory"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;fi</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;[&nbsp;-z&nbsp;"${URL##*/}"&nbsp;]&#059;&nbsp;then</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;URL=${URL}${DEFINDEX}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;fi</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;DIR="`dirname&nbsp;$URL`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;[&nbsp;!&nbsp;-d&nbsp;${DOCROOT}/${DIR}&nbsp;]&#059;&nbsp;then</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log&nbsp;${PEER}&nbsp;-&nbsp;404&nbsp;0</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print_error&nbsp;404&nbsp;"Directory&nbsp;not&nbsp;found"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;else</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;cd&nbsp;${DOCROOT}/${DIR}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;NURL="`pwd`/`basename&nbsp;${URL}`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;URL=${NURL}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;fi</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;[&nbsp;!&nbsp;-f&nbsp;${URL}&nbsp;]&#059;&nbsp;then</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log&nbsp;${PEER}&nbsp;-&nbsp;404&nbsp;0</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print_error&nbsp;404&nbsp;"Document&nbsp;not&nbsp;found"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;fi</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;print_header</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;guess_content_type&nbsp;${URL}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;LEN="`ls&nbsp;-l&nbsp;${URL}&nbsp;|&nbsp;tr&nbsp;-s&nbsp;'&nbsp;'&nbsp;|&nbsp;cut&nbsp;-d&nbsp;'&nbsp;'&nbsp;-f&nbsp;5`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;-e&nbsp;"Content-length:&nbsp;$LEN\r\n\r"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;log&nbsp;${PEER}&nbsp;-&nbsp;200&nbsp;${LEN}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;cat&nbsp;${URL}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;sleep&nbsp;3</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>read_request()&nbsp;{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;DIRT</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;local&nbsp;COMMAND</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;read&nbsp;REQUEST</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;read&nbsp;DIRT</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;REQ_DATE="`date&nbsp;+"%d/%b/%Y:%H:%M:%S&nbsp;%z"`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;REQUEST="`echo&nbsp;${REQUEST}&nbsp;|&nbsp;tr&nbsp;-s&nbsp;[:blank:]`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;COMMAND="`echo&nbsp;${REQUEST}&nbsp;|&nbsp;cut&nbsp;-d&nbsp;'&nbsp;'&nbsp;-f&nbsp;1`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;URL="`echo&nbsp;${REQUEST}&nbsp;|&nbsp;cut&nbsp;-d&nbsp;'&nbsp;'&nbsp;-f&nbsp;2`"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;PROTOCOL="`echo&nbsp;${REQUEST}&nbsp;|&nbsp;cut&nbsp;-d&nbsp;'&nbsp;'&nbsp;-f&nbsp;3`"</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;case&nbsp;$COMMAND&nbsp;in</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;HEAD)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print_error&nbsp;501&nbsp;"Not&nbsp;implemented&nbsp;(yet)"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;GET)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;do_get</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;print_error&nbsp;501&nbsp;"Not&nbsp;Implemented"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;esac</code><br>
<code>}</code><br>
<code>&nbsp;</code><br>
<code>#</code><br>
<code>#&nbsp;It&nbsp;was&nbsp;supposed&nbsp;to&nbsp;be&nbsp;clean&nbsp;-&nbsp;without&nbsp;any&nbsp;non-standard&nbsp;utilities</code><br>
<code>#&nbsp;but&nbsp;I&nbsp;want&nbsp;some&nbsp;logging&nbsp;where&nbsp;the&nbsp;connections&nbsp;come&nbsp;from,&nbsp;so</code><br>
<code>#&nbsp;I&nbsp;use&nbsp;just&nbsp;this&nbsp;one&nbsp;utility&nbsp;to&nbsp;get&nbsp;the&nbsp;peer&nbsp;address</code><br>
<code>#</code><br>
<code>#&nbsp;This&nbsp;is&nbsp;from&nbsp;the&nbsp;netpipes&nbsp;package</code><br>
<code>PEER="`getpeername&nbsp;|&nbsp;cut&nbsp;-d&nbsp;'&nbsp;'&nbsp;-f&nbsp;1`"</code><br>
<code>&nbsp;</code><br>
<code>read_request</code><br>
<code>&nbsp;</code><br>
<code>exit&nbsp;0</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Now run <TT>
<FONT COLOR="#0000ff">telnet&nbsp;localhost&nbsp;80</FONT></TT>, as in Section <A HREF="node29.html#sec:telnetcnn">26.2</A>.
If that works and your log files are being properly appended (use <TT>
<FONT COLOR="#0000ff">tail&nbsp;-f&nbsp;</FONT></TT>...),
you can try to connect to <I><TT><A NAME="tex2html50"
  HREF="http://localhost/">http://localhost/</A></TT></I> with a web browser like Netscape.

<P>
Notice also that the command <TT>
<FONT COLOR="#0000ff">getsockname</FONT></TT> (which
tells you which of your own IP addresses the remote client connected
to) could allow the script to serve pages from a different directory for
each IP address. This is <I>virtual domains</I> in a nutshell. <FONT COLOR="#ffa500">[Groovy,
baby, I'm in a giant nutshell.... how do I get out?]</FONT>
<P>

<H1><A NAME="SECTION003920000000000000000">
36.2 Installing and Configuring Apache</A>
</H1>

<P>
Because all distributions package Apache in a different way, here I
assume Apache to have been installed from its source tree, rather
than from a <TT>
<FONT COLOR="#0000ff">.deb</FONT></TT> or <TT>
<FONT COLOR="#0000ff">.rpm</FONT></TT> package.
You can refer to Section <A HREF="node27.html#sec:gnupackages">24.1</A> on how to install Apache
from its source <TT>
<FONT COLOR="#0000ff">.tar.gz</FONT></TT> file like any other GNU package.
(You can even install it under Windows, Windows NT, or OS/2.)
The source tree is, of course, available from
<EM>The Apache Home Page</EM> <I>&lt;<TT><A NAME="tex2html51"
  HREF="http://www.apache.org">http://www.apache.org</A></TT>&gt;</I>.
Here I assume you have installed it in <TT>
<FONT COLOR="#0000ff">&#45;&#45;prefix=/opt/apache/</FONT></TT>.
In the process, Apache will have dumped a huge reference manual
into
<TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/manual/</FONT></TT>.

<P>

<H2><A NAME="SECTION003921000000000000000">
36.2.1 Sample <TT>
<FONT COLOR="#0000ff">httpd.conf</FONT></TT></A>
</H2>

<P>
Apache has several legacy configuration files: <TT>
<FONT COLOR="#0000ff">access.conf</FONT></TT> and
<TT>
<FONT COLOR="#0000ff">srm.conf</FONT></TT> are two of them. These files are now deprecated and should
be left empty. A single configuration file <TT>
<FONT COLOR="#0000ff">/opt/apache/conf/httpd.conf</FONT></TT>
may contain at minimum:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>35</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>40</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>ServerType&nbsp;standalone</code><br>
<code>ServerRoot&nbsp;"/opt/apache"</code><br>
<code>PidFile&nbsp;/opt/apache/logs/httpd.pid</code><br>
<code>ScoreBoardFile&nbsp;/opt/apache/logs/httpd.scoreboard</code><br>
<code>Port&nbsp;80</code><br>
<code>User&nbsp;nobody</code><br>
<code>Group&nbsp;nobody</code><br>
<code>HostnameLookups&nbsp;Off</code><br>
<code>ServerAdmin&nbsp;webmaster@cranzgot.co.za</code><br>
<code>UseCanonicalName&nbsp;On</code><br>
<code>ServerSignature&nbsp;On</code><br>
<code>DefaultType&nbsp;text/plain</code><br>
<code>ErrorLog&nbsp;/opt/apache/logs/error_log</code><br>
<code>LogLevel&nbsp;warn</code><br>
<code>LogFormat&nbsp;"%h&nbsp;%l&nbsp;%u&nbsp;%t&nbsp;\"%r\"&nbsp;%&#062;s&nbsp;%b"&nbsp;common</code><br>
<code>CustomLog&nbsp;/opt/apache/logs/access_log&nbsp;common</code><br>
<code>DocumentRoot&nbsp;"/opt/apache/htdocs"</code><br>
<code>DirectoryIndex&nbsp;index.html</code><br>
<code>AccessFileName&nbsp;.htaccess</code><br>
<code>&#060;Directory&nbsp;/&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;FollowSymLinks</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;None</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;Deny,Allow</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Deny&nbsp;from&nbsp;All</code><br>
<code>&#060;/Directory&#062;</code><br>
<code>&#060;Files&nbsp;~&nbsp;"^\.ht"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Deny&nbsp;from&nbsp;all</code><br>
<code>&#060;/Files&#062;</code><br>
<code>&#060;Directory&nbsp;"/opt/apache/htdocs"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;Indexes&nbsp;FollowSymLinks&nbsp;MultiViews</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;All</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
<code>&#060;Directory&nbsp;"/opt/apache/htdocs/home/*/www"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;Indexes&nbsp;MultiViews</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;None</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
<code>UserDir&nbsp;/opt/apache/htdocs/home/*/www</code><br>
</FONT></TD></TR></TABLE><P>

<P>
With the config file ready, you can move the
<TT>
<FONT COLOR="#0000ff">index.html</FONT></TT> file above to <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/</FONT></TT>.
You will notice the complete Apache manual and a demo
page already installed there; you can move them to another directory
for the time being. Now run

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>/opt/apache/bin/httpd&nbsp;-X</code><br>
</FONT></TD></TR></TABLE><P>
and then point your web browser to <I><TT><A NAME="tex2html52"
  HREF="http://localhost/">http://localhost/</A></TT></I>
as before.

<P>

<H2><A NAME="SECTION003922000000000000000">
36.2.2 Common directives</A>
</H2>

<P>
Here is a description of the options. Each option is called
a <I>directive</I> in Apache terminology. A complete
list of basic directives is in the file <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/manual/mod/core.html</FONT></TT>.
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ServerType</FONT></TT></STRONG></DT>
<DD>As discussed in Section <A HREF="node32.html#sec:servinetdstand">29.2</A>,
some services can run standalone or from <TT>
<FONT COLOR="#0000ff">inetd</FONT></TT> (or <TT>
<FONT COLOR="#0000ff">xinetd</FONT></TT>).
This directive can be exactly <TT>
<FONT COLOR="#0000ff">standalone</FONT></TT> or <TT>
<FONT COLOR="#0000ff">inetd</FONT></TT>. If you choose
<TT>
<FONT COLOR="#0000ff">inetd</FONT></TT>, you will need to add an appropriate line into your <TT>
<FONT COLOR="#0000ff">inetd</FONT></TT>
configuration, although a web server should almost certainly choose standalone
mode.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ServerRoot</FONT></TT></STRONG></DT>
<DD>This is the directory
superstructure <FONT COLOR="#ffa500">[See page <A HREF="node20.html#page:directsuper"><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>.]</FONT> under which
Apache is installed. It will always be the same as the value passed to <TT>
<FONT COLOR="#0000ff">&#45;&#45;prefix=</FONT></TT>.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">PidFile</FONT></TT></STRONG></DT>
<DD>Many system
services store the process ID in a file for
shutdown and monitoring purposes. On most distributions, the
file is <TT>
<FONT COLOR="#0000ff">/var/run/httpd.pid</FONT></TT>.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ScoreBoardFile</FONT></TT></STRONG></DT>
<DD>This option is used for communication between Apache parent and child
processes on some non-U<SMALL>NIX</SMALL> systems.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Port</FONT></TT></STRONG></DT>
<DD>This is the TCP port for standalone servers to listen on.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">User</FONT></TT>, <TT>
<FONT COLOR="#0000ff">Group</FONT></TT></STRONG></DT>
<DD>This option is
important for security. It forces <TT>
<FONT COLOR="#0000ff">httpd</FONT></TT> to user
<TT>
<FONT COLOR="#0000ff">nobody</FONT></TT> privileges. If the web server is ever hacked, the attack will not be
able to gain more than the privileges of the <TT>
<FONT COLOR="#0000ff">nobody</FONT></TT> user.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">HostnameLookups</FONT></TT></STRONG></DT>
<DD>To
force a reverse DNS lookup
on every connecting host, set this directive to <TT>
<FONT COLOR="#0000ff">on</FONT></TT>. To force
a forward lookup on every reverse lookup, set this to <TT>
<FONT COLOR="#0000ff">double</FONT></TT>. This option is
for logging purposes since access control does a reverse and forward reverse lookup
anyway if required. It should certainly be <TT>
<FONT COLOR="#0000ff">off</FONT></TT> if you want to reduce latency.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ServerAdmin</FONT></TT></STRONG></DT>
<DD>Error messages include this email address.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">UseCanonicalName</FONT></TT></STRONG></DT>
<DD>If Apache has to return a URL for any reason,
it will normally return the full name of the server. Setting to <TT>
<FONT COLOR="#0000ff">off</FONT></TT>
uses the very host name sent by the client.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ServerSignature</FONT></TT></STRONG></DT>
<DD>Add the server name to HTML error messages.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">DefaultType</FONT></TT></STRONG></DT>
<DD>All files returned to the client have a type field
specifying how the file should be displayed. If Apache cannot deduce the type,
it assumes the MIME Type to be <TT>
<FONT COLOR="#0000ff">text/plain</FONT></TT>. See Section <A HREF="node15.html#sec:mimeencap">12.6.2</A>
for a discussion of MIME types.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ErrorLog</FONT></TT></STRONG></DT>
<DD>Where errors get logged, usually <TT>
<FONT COLOR="#0000ff">/var/log/httpd/error_log</FONT></TT>
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">LogLevel</FONT></TT></STRONG></DT>
<DD>How much info to log.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">LogFormat</FONT></TT></STRONG></DT>
<DD>Define a new log format. Here we
defined a log format and call
it <TT>
<FONT COLOR="#0000ff">common</FONT></TT>. Multiple lines are allowed. Lots of interesting information can actually be
logged: See <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/manual/mod/mod_log_config.html</FONT></TT> for a full description.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">CustomLog</FONT></TT></STRONG></DT>
<DD>The log file name and its (previously defined) format.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">DocumentRoot</FONT></TT></STRONG></DT>
<DD>This directive specifies the top-level
directory that client connections
will see. The string <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/</FONT></TT> is prepended to any file lookup, and
hence a URL <I><TT><A NAME="tex2html53"
  HREF="http://localhost/manual/index.html.en">http://localhost/manual/index.html.en</A></TT></I> will return the file
<TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/manual/index.html.en</FONT></TT>.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">DirectoryIndex</FONT></TT></STRONG></DT>
<DD>This directive gives the default file to try serve for
URLs that contain only a directory name. If a file <TT>
<FONT COLOR="#0000ff">index.html</FONT></TT> does not
exist under that directory, an index of the directory is sent to the client.
Other common configurations use <TT>
<FONT COLOR="#0000ff">index.htm</FONT></TT> or <TT>
<FONT COLOR="#0000ff">default.html</FONT></TT>.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">AccessFileName</FONT></TT></STRONG></DT>
<DD>Before serving a file to a client, Apache reads
additional directives from a file <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT> in the same directory as the requested
file. If a parent directory contains a <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT> instead, this one will take
priority. The <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT> file contains directives that limit access to the
directory, as discussed below.
</DD>
</DL>

<P>
The above is merely the general configuration of Apache. To actually
serve pages, you need to define directories, each with a particular purpose,
containing particular HTML or graphic files.
The Apache configuration file is very much like an HTML document.
Sections are started with <TT>
<FONT COLOR="#0000ff">&lt;</FONT></TT><I>section</I><TT>
<FONT COLOR="#0000ff">&nbsp;</FONT></TT><I>parameter</I><TT>
<FONT COLOR="#0000ff">&gt;</FONT></TT>
and ended with <TT>
<FONT COLOR="#0000ff">&lt;/</FONT></TT><I>section</I><TT>
<FONT COLOR="#0000ff">&gt;</FONT></TT>. The most common directive
of this sort is <TT>
<FONT COLOR="#0000ff">&lt;Directory&nbsp;/</FONT></TT><I>directory</I><TT>
<FONT COLOR="#0000ff">&gt;</FONT></TT>
which does such
directory definition. Before defining any directories, we need to limit
access to the root directory. This control is critical for security.

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;Directory&nbsp;/&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;FollowSymLinks</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Deny&nbsp;from&nbsp;All</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;Deny,Allow</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;None</code><br>
<code>&#060;/Directory&#062;</code><br>
</FONT></TD></TR></TABLE><P>
This configuration tells Apache about the root directory, giving clients
very restrictive access to it. The directives are <FONT COLOR="#ffa500">[Some of these
are extracted from the Apache manual.]</FONT>:
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Options</FONT></TT></STRONG></DT>
<DD>The <TT>
<FONT COLOR="#0000ff">Options</FONT></TT> directive controls which server features are available in
a particular directory. There is also the syntax <TT>
<FONT COLOR="#0000ff">+</FONT></TT><I>option</I> or
<TT>
<FONT COLOR="#0000ff">-</FONT></TT><I>option</I> to include the options of the parent directory,
for example, <TT>
<FONT COLOR="#0000ff">Options&nbsp;+FollowSymLinks&nbsp;-Indexes</FONT></TT>.
<DL>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">FollowSymLinks</FONT></TT></STRONG></DT>
<DD>The server will follow any symbolic links beneath the directory. Be careful
about what symbolic links you have beneath directories with <TT>
<FONT COLOR="#0000ff">FollowSymLinks</FONT></TT>.
You can, for example, give everyone access to the root directory by having 
a link <TT>
<FONT COLOR="#0000ff">../../../</FONT></TT> under <TT>
<FONT COLOR="#0000ff">htdocs</FONT></TT>--not what you want.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">ExecCGI</FONT></TT></STRONG></DT>
<DD>Execution of CGI scripts is permitted.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Includes</FONT></TT></STRONG></DT>
<DD>Server-side includes are permitted (more on this later).
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">IncludesNOEXEC</FONT></TT></STRONG></DT>
<DD>Server-side includes are permitted, but the <TT>
<FONT COLOR="#0000ff">#exec</FONT></TT> command and
<TT>
<FONT COLOR="#0000ff">#include</FONT></TT> of CGI scripts are disabled.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Indexes</FONT></TT></STRONG></DT>
<DD>If a client asks for a directory by name and no <TT>
<FONT COLOR="#0000ff">index.html</FONT></TT>
file (or whatever <TT>
<FONT COLOR="#0000ff">DirectoryIndex</FONT></TT> file you specified) is present,
then a pretty listing of the contents of that directory is created and
returned. For security you may want to turn this option off.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">MultiViews</FONT></TT></STRONG></DT>
<DD>Content-negotiated MultiViews are allowed (more on this later).
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">SymLinksIfOwnerMatch</FONT></TT></STRONG></DT>
<DD>The server will only follow symbolic links for which the target
file or directory is owned by the same user ID as the link
(more on this later).
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">All</FONT></TT></STRONG></DT>
<DD>All options except for <TT>
<FONT COLOR="#0000ff">MultiViews</FONT></TT>. This is the default setting.
</DD>
</DL>
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Deny</FONT></TT></STRONG></DT>
<DD>Hosts that are not allowed to connect.
You can specify a host name or IP address, for example, as:
</DD>
</DL>

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>Deny&nbsp;from&nbsp;10.1.2.3</code><br>
<code>Deny&nbsp;from&nbsp;192.168.5.0/24</code><br>
<code>Deny&nbsp;from&nbsp;cranzgot.co.za</code><br>
</FONT></TD></TR></TABLE><P>
<DL>
<DT></DT>
<DD>which will deny access
to <TT>
<FONT COLOR="#0000ff">10.1.2.3</FONT></TT>, all hosts beginning with <TT>
<FONT COLOR="#0000ff">192.168.5.</FONT></TT>,
and all hosts ending in <TT>
<FONT COLOR="#0000ff">.cranzgot.co.za</FONT></TT>, including the host <TT>
<FONT COLOR="#0000ff">cranzgot.co.za</FONT></TT>.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Allow</FONT></TT></STRONG></DT>
<DD>Hosts that are allowed to connect. This directive uses the same
syntax as <TT>
<FONT COLOR="#0000ff">Deny</FONT></TT>.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">Order</FONT></TT></STRONG></DT>
<DD>If order is <TT>
<FONT COLOR="#0000ff">Deny,Allow</FONT></TT>, then the <TT>
<FONT COLOR="#0000ff">Deny</FONT></TT> directives
are checked first and any client that does not match a
<TT>
<FONT COLOR="#0000ff">Deny</FONT></TT> directive or does match an <TT>
<FONT COLOR="#0000ff">Allow</FONT></TT> directive
will be <I>allowed</I> access to the server.

<P>
If order is <TT>
<FONT COLOR="#0000ff">Allow,Deny</FONT></TT>, then the <TT>
<FONT COLOR="#0000ff">Allow</FONT></TT> directives
are checked first and any client that does not match an
<TT>
<FONT COLOR="#0000ff">Allow</FONT></TT> directive or does match a <TT>
<FONT COLOR="#0000ff">Deny</FONT></TT> directive
will be <I>denied</I> access to the server.
</DD>
<DT><STRONG><TT>
<FONT COLOR="#0000ff">AllowOverride</FONT></TT></STRONG></DT>
<DD>In addition to the directives specified
here, additional directives will be read from the file specified by
<TT>
<FONT COLOR="#0000ff">AccessFileName</FONT></TT>, usually called <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT>. This file would
usually exist alongside your <TT>
<FONT COLOR="#0000ff">.html</FONT></TT> files or otherwise in a
parent directory. If the file exists, its contents are read into the
current <TT>
<FONT COLOR="#0000ff">&lt;Directory</FONT></TT><I>&nbsp;...</I><TT>
<FONT COLOR="#0000ff">&gt;</FONT></TT> directive.
<TT>
<FONT COLOR="#0000ff">AllowOverride</FONT></TT> says what directives the <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT> file is
allowed to squash. The complete list can be found in
<TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/manual/mod/core.html</FONT></TT>.
</DD>
</DL>

<P>
You can see that we give very restrictive <TT>
<FONT COLOR="#0000ff">Options</FONT></TT>
to the root directory, as well as very restrictive access. The only server
feature we allow is <TT>
<FONT COLOR="#0000ff">FollowSymLinks</FONT></TT>, then we <TT>
<FONT COLOR="#0000ff">Deny</FONT></TT>
any access, and then we remove the possibility that a <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT>
file could override our restrictions.

<P>
The <TT>
<FONT COLOR="#0000ff">&lt;Files&nbsp;</FONT></TT><I>...</I><TT>
<FONT COLOR="#0000ff">&gt;</FONT></TT> directive sets restrictions
on all files matching a particular regular expression. As a security measure,
we use it to prevent access to all <TT>
<FONT COLOR="#0000ff">.htaccess</FONT></TT> files as follows:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;Files&nbsp;~&nbsp;"^\.ht"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Deny&nbsp;from&nbsp;all</code><br>
<code>&#060;/Files&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>
We are now finally ready to add actual web page directories.
These take a less restrictive set of access controls:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;Directory&nbsp;"/opt/apache/htdocs"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;Indexes&nbsp;FollowSymLinks&nbsp;MultiViews</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;All</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>

<H2><A NAME="SECTION003923000000000000000">
36.2.3 User HTML directories</A>
</H2>

<P>
Our users may require that Apache know about their
private web page directories <TT>
<FONT COLOR="#0000ff">~/www/</FONT></TT>. This is easy to support
with the special <TT>
<FONT COLOR="#0000ff">UserDir</FONT></TT> directive:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;Directory&nbsp;"/opt/apache/htdocs/home/*/www"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;Indexes&nbsp;MultiViews</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;None</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
<code>UserDir&nbsp;/opt/apache/htdocs/home/*/www</code><br>
</FONT></TD></TR></TABLE><P>
For this feature to work, you must symlink <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/home</FONT></TT> to <TT>
<FONT COLOR="#0000ff">/home</FONT></TT>,
and create a directory <TT>
<FONT COLOR="#0000ff">www/</FONT></TT> under each user's home directory.
Hitting the URL <I><TT><A NAME="tex2html54"
  HREF="http://localhost/~jack/index.html">http://localhost/~jack/index.html</A></TT></I> will then retrieve
the file <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/home/jack/www/index.html</FONT></TT>.
You will find that Apache gives a <TT>
<FONT COLOR="#0000ff">Forbidden</FONT></TT> error message when
you try to do this. This is probably because <TT>
<FONT COLOR="#0000ff">jack</FONT></TT>'s
home directory's permissions are too restrictive. Your choices
vary between now making <TT>
<FONT COLOR="#0000ff">jack</FONT></TT>'s home directory less restricted
or increasing the privileges of Apache. Running Apache under the <TT>
<FONT COLOR="#0000ff">www</FONT></TT>
group by using <TT>
<FONT COLOR="#0000ff">Group&nbsp;www</FONT></TT>, and then running

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>groupadd&nbsp;-g&nbsp;65&nbsp;www</code><br>
<code>chown&nbsp;jack:www&nbsp;/home/jack&nbsp;/home/jack/www</code><br>
<code>chmod&nbsp;0750&nbsp;/home/jack&nbsp;/home/jack/www</code><br>
</FONT></TD></TR></TABLE><P>
is a reasonable compromise.

<P>

<H2><A NAME="SECTION003924000000000000000">
36.2.4 Aliasing</A>
</H2>

<P>
Sometimes, HTML documents will want to refer to a file or graphic
by using a simple prefix, rather than a long directory name. Other
times, you want two different references to source the same file.
The <TT>
<FONT COLOR="#0000ff">Alias</FONT></TT> directive creates virtual links between directories.
For example, adding the following line, means that a URL <TT>
<FONT COLOR="#0000ff">/icons/bomb.gif</FONT></TT>
will serve the file <TT>
<FONT COLOR="#0000ff">/opt/apache/icons/bomb.gif</FONT></TT>:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>Alias&nbsp;/icons/&nbsp;"/opt/apache/icons/"</code><br>
</FONT></TD></TR></TABLE><P>
We do, of course, need to tell Apache about this directory:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;Directory&nbsp;"/opt/apache/icons"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;None</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;None</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>

<H2><A NAME="SECTION003925000000000000000">
36.2.5 Fancy indexes</A>
</H2>

<P>
You will find the directory lists generated by the preceding
configuration rather bland. The directive

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>IndexOptions&nbsp;FancyIndexing</code><br>
</FONT></TD></TR></TABLE><P>
causes nice descriptive icons to be printed to the left of the file name.
What icons match what file types is a trick issue. You can start with:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>AddIconByEncoding&nbsp;(CMP,/icons/compressed.gif)&nbsp;x-compress&nbsp;x-gzip</code><br>
<code>AddIconByType&nbsp;(TXT,/icons/text.gif)&nbsp;text/*</code><br>
<code>AddIconByType&nbsp;(IMG,/icons/image2.gif)&nbsp;image/*</code><br>
<code>AddIconByType&nbsp;(SND,/icons/sound2.gif)&nbsp;audio/*</code><br>
<code>AddIconByType&nbsp;(VID,/icons/movie.gif)&nbsp;video/*</code><br>
<code>AddIcon&nbsp;/icons/compressed.gif&nbsp;.Z&nbsp;.z&nbsp;.tgz&nbsp;.gz&nbsp;.zip</code><br>
<code>AddIcon&nbsp;/icons/a.gif&nbsp;.ps&nbsp;.eps</code><br>
<code>AddIcon&nbsp;/icons/layout.gif&nbsp;.html&nbsp;.shtml&nbsp;.htm</code><br>
</FONT></TD></TR></TABLE><P>
This requires the <TT>
<FONT COLOR="#0000ff">Alias</FONT></TT> directive above to be present.
The default Apache configuration contains a far more extensive
map of file types.

<P>

<H2><A NAME="SECTION003926000000000000000">
36.2.6 Encoding and language negotiation</A>
</H2>

<P>
You can get Apache to serve
<TT>
<FONT COLOR="#0000ff">gzip</FONT></TT>ped files
with this:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>AddEncoding&nbsp;x-compress&nbsp;Z</code><br>
<code>AddEncoding&nbsp;x-gzip&nbsp;gz</code><br>
</FONT></TD></TR></TABLE><P>
Now if a client requests a file <TT>
<FONT COLOR="#0000ff">index.html</FONT></TT>, but only a file
<TT>
<FONT COLOR="#0000ff">index.html.gz</FONT></TT> exists, Apache decompresses it on-the-fly.
Note that you must have the <TT>
<FONT COLOR="#0000ff">MultiViews</FONT></TT> options enabled.

<P>
The next options cause Apache to serve <TT>
<FONT COLOR="#0000ff">index.html.</FONT></TT><I>language-code</I>
when <TT>
<FONT COLOR="#0000ff">index.html</FONT></TT> is requested, filling in the preferred language code
sent by the web browser. Adding these directives causes your Apache manual
to display correctly and will properly show documents that have non-English
translations. Here also, the <TT>
<FONT COLOR="#0000ff">MultiViews</FONT></TT> must be present.

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>AddLanguage&nbsp;en&nbsp;.en</code><br>
<code>AddLanguage&nbsp;da&nbsp;.dk</code><br>
<code>AddLanguage&nbsp;nl&nbsp;.nl</code><br>
<code>AddLanguage&nbsp;et&nbsp;.ee</code><br>
<code>AddLanguage&nbsp;fr&nbsp;.fr</code><br>
<code>AddLanguage&nbsp;de&nbsp;.de</code><br>
<code>AddLanguage&nbsp;el&nbsp;.el</code><br>
<code>AddLanguage&nbsp;ja&nbsp;.ja</code><br>
<code>AddLanguage&nbsp;ru&nbsp;.ru</code><br>
<code>LanguagePriority&nbsp;en&nbsp;da&nbsp;nl&nbsp;et&nbsp;fr&nbsp;de&nbsp;el&nbsp;ja&nbsp;ru</code><br>
</FONT></TD></TR></TABLE><P>
The <TT>
<FONT COLOR="#0000ff">LanguagePriority</FONT></TT> directive indicates the preferred language
if the browser did not specify any.

<P>
Some files might contain a <TT>
<FONT COLOR="#0000ff">.koi8-r</FONT></TT> extension,
indicating a Russian character set encoding for this file. Many
languages have such custom character sets. Russian files are named
<I>webpage</I><TT>
<FONT COLOR="#0000ff">.html.ru.koi8-r</FONT></TT>. Apache must tell the web browser
about the encoding type, based on the extension. Here are directives
for Japanese, Russian, and UTF-8 <FONT COLOR="#ffa500">[UTF-8 is a Unicode character set
encoding useful for any language.]</FONT>, as follows:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>AddCharset&nbsp;ISO-2022-JP&nbsp;&nbsp;.jis</code><br>
<code>AddCharset&nbsp;KOI8-R&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.koi8-r</code><br>
<code>AddCharset&nbsp;UTF-8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;.utf8</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Once again, the default Apache configuration contains a far
more extensive map of languages and character sets.

<P>

<H2><A NAME="SECTION003927000000000000000">
36.2.7 Server-side includes -- SSI</A>
</H2>

<P>
Apache actually has a built-in programming language that interprets <TT>
<FONT COLOR="#0000ff">.shtml</FONT></TT>
files as scripts. The output of such a script is returned to the client.
Most of a typical <TT>
<FONT COLOR="#0000ff">.shtml</FONT></TT> file will be ordinary HTML, which will
be served unmodified. However, lines like

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;!--#echo&nbsp;var="DATE_LOCAL"&nbsp;--&#062;</code><br>
</FONT></TD></TR></TABLE><P>
will be interpreted, and their output <I>included</I> into the
HTML--hence the name <I>server-side includes</I>. Server-side includes are ideal
for HTML pages that contain mostly static HTML with small bits of dynamic
content. To demonstrate, add the following to your <TT>
<FONT COLOR="#0000ff">httpd.conf</FONT></TT>:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>AddType&nbsp;text/html&nbsp;.shtml</code><br>
<code>AddHandler&nbsp;server-parsed&nbsp;.shtml</code><br>
<code>&#060;Directory&nbsp;"/opt/apache/htdocs/ssi"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;Includes</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;None</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
</FONT></TD></TR></TABLE><P>
Create a directory <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/ssi</FONT></TT> with the index
file <TT>
<FONT COLOR="#0000ff">index.shtml</FONT></TT>:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;HTML&#062;</code><br>
<code>The&nbsp;date&nbsp;today&nbsp;is&nbsp;&#060;!--#echo&nbsp;var="DATE_LOCAL"&nbsp;--&#062;.&#060;P&#062;</code><br>
<code>Here&nbsp;is&nbsp;a&nbsp;directory&nbsp;listing:&#060;br&#062;</code><br>
<code>&nbsp;&#060;PRE&#062;</code><br>
<code>&nbsp;&nbsp;&#060;!--#exec&nbsp;cmd="ls&nbsp;-al"&nbsp;--&#062;</code><br>
<code>&nbsp;&#060;/PRE&#062;</code><br>
<code>&#060;!--#include&nbsp;virtual="footer.html"&nbsp;--&#062;</code><br>
<code>&#060;/HTML&#062;</code><br>
</FONT></TD></TR></TABLE><P>
and then a file <TT>
<FONT COLOR="#0000ff">footer.html</FONT></TT> containing anything you
like. It is obvious how useful this procedure is for creating many documents with
the same banner by means of a <TT>
<FONT COLOR="#0000ff">#include</FONT></TT> statement. If you are wondering
what other variables you can print besides <TT>
<FONT COLOR="#0000ff">DATE_LOCAL</FONT></TT>, try the
following:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;HTML&#062;</code><br>
<code>&nbsp;&#060;PRE&#062;</code><br>
<code>&nbsp;&nbsp;&#060;!--#printenv&nbsp;--&#062;</code><br>
<code>&nbsp;&#060;/PRE&#062;</code><br>
<code>&#060;/HTML&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>
You can also goto <I><TT><A NAME="tex2html55"
  HREF="http://localhost/manual/howto/ssi.html">http://localhost/manual/howto/ssi.html</A></TT></I>
to see some other examples.

<P>

<H2><A NAME="SECTION003928000000000000000">
36.2.8 CGI -- Common Gateway Interface</A>
</H2>

<P>

(I have actually never managed to figure out why CGI is called CGI.) CGI is
where a URL points to a script. What comes up in your browser is the
output of the script (were it to be executed) instead of the contents
of the script itself. To try this, create a file <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/test.cgi</FONT></TT>:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>&nbsp;</code><br>
<code>echo&nbsp;'Content-type:&nbsp;text/html'</code><br>
<code>echo</code><br>
<code>echo&nbsp;'&#060;HTML&#062;'</code><br>
<code>echo&nbsp;'&nbsp;&#060;HEAD&#062;'</code><br>
<code>echo&nbsp;'&nbsp;&nbsp;&#060;TITLE&#062;My&nbsp;First&nbsp;CGI&#060;/TITLE&#062;'</code><br>
<code>echo&nbsp;'&nbsp;&#060;/HEAD&#062;'</code><br>
<code>echo&nbsp;'&nbsp;&#060;BODY&nbsp;bgcolor=#CCCCCC&nbsp;text="#000000"&#062;'</code><br>
<code>echo&nbsp;'This&nbsp;is&nbsp;my&nbsp;first&nbsp;CGI&#060;P&#062;'</code><br>
<code>echo&nbsp;'Please&nbsp;visit'</code><br>
<code>echo&nbsp;'&nbsp;&nbsp;&#060;A&nbsp;HREF="http://rute.sourceforge.net/"&#062;'</code><br>
<code>echo&nbsp;'&nbsp;&nbsp;&nbsp;The&nbsp;Rute&nbsp;Home&nbsp;Page'</code><br>
<code>echo&nbsp;'&nbsp;&nbsp;&#060;/A&#062;'</code><br>
<code>echo&nbsp;'for&nbsp;more&nbsp;info.&#060;/P&#062;'</code><br>
<code>echo&nbsp;'&nbsp;&#060;/BODY&#062;'</code><br>
<code>echo&nbsp;'&#060;/HTML&#062;'</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Make this script executable with <TT>
<FONT COLOR="#0000ff">chmod&nbsp;a+x&nbsp;test.cgi</FONT></TT> and
test the output by running it on the command-line. Add the line

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>AddHandler&nbsp;cgi-script&nbsp;.cgi</code><br>
</FONT></TD></TR></TABLE><P>
to your <TT>
<FONT COLOR="#0000ff">httpd.conf</FONT></TT> file. Next, modify your <TT>
<FONT COLOR="#0000ff">Options</FONT></TT>
for the directory <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs</FONT></TT> to include <TT>
<FONT COLOR="#0000ff">ExecCGI</FONT></TT>,
like this:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;Directory&nbsp;"/opt/apache/htdocs"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Options&nbsp;Indexes&nbsp;FollowSymLinks&nbsp;MultiViews&nbsp;ExecCGI</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;AllowOverride&nbsp;All</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Order&nbsp;allow,deny</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;Allow&nbsp;from&nbsp;all</code><br>
<code>&#060;/Directory&#062;</code><br>
</FONT></TD></TR></TABLE><P>

<P>
After restarting Apache you should be able to visit the URL
<I><TT><A NAME="tex2html56"
  HREF="http://localhost/test.cgi">http://localhost/test.cgi</A></TT></I>. If you run into problems, don't forget
to run <TT>
<FONT COLOR="#0000ff">tail&nbsp;/opt/apache/logs/error_log</FONT></TT> to get a full report.

<P>
To get a full list of environment variables available to your
CGI program, try the following script:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>&nbsp;</code><br>
<code>echo&nbsp;'Content-type:&nbsp;text/html'</code><br>
<code>echo</code><br>
<code>echo&nbsp;'&#060;HTML&#062;'</code><br>
<code>echo&nbsp;'&#060;PRE&#062;'</code><br>
<code>set</code><br>
<code>echo&nbsp;'&#060;/PRE&#062;'</code><br>
<code>echo&nbsp;'&#060;/HTML&#062;'</code><br>
</FONT></TD></TR></TABLE><P>
The script will show ordinary <TT>
<FONT COLOR="#0000ff">bash</FONT></TT> environment variables as well
as more interesting variables like
<TT>
<FONT COLOR="#0000ff">QUERY_STRING</FONT></TT>: Change your script to

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>&nbsp;</code><br>
<code>echo&nbsp;'Content-type:&nbsp;text/html'</code><br>
<code>echo</code><br>
<code>echo&nbsp;'&#060;HTML&#062;'</code><br>
<code>echo&nbsp;'&#060;PRE&#062;'</code><br>
<code>echo&nbsp;$QUERY_STRING</code><br>
<code>echo&nbsp;'&#060;/PRE&#062;'</code><br>
<code>echo&nbsp;'&#060;/HTML&#062;'</code><br>
</FONT></TD></TR></TABLE><P>
and then go to the URL <I><TT><A NAME="tex2html57"
  HREF="http://localhost/test/test.cgi?xxx=2&amp;yyy=3">http://localhost/test/test.cgi?xxx=2&amp;yyy=3</A></TT></I>.
It is easy to see how variables can be passed to the shell script.

<P>
The preceding example is not very interesting. However, it gets useful
when scripts have complex logic or can access information that Apache
can't access on its own. In Chapter <A HREF="node41.html#chap:postgres">38</A> we see how to deploy
an SQL database. When you
have covered SQL, you can come back here and
replace your CGI script with,

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>&nbsp;</code><br>
<code>echo&nbsp;'Content-type:&nbsp;text/html'</code><br>
<code>echo</code><br>
<code>&nbsp;</code><br>
<code>psql&nbsp;-d&nbsp;template1&nbsp;-H&nbsp;-c&nbsp;"SELECT&nbsp;*&nbsp;FROM&nbsp;pg_tables&#059;"</code><br>
</FONT></TD></TR></TABLE><P>
This script will dump the table list of the <TT>
<FONT COLOR="#0000ff">template1</FONT></TT>
database if it exists. Apache will have to run as a user that can
access this database, which means changing <TT>
<FONT COLOR="#0000ff">User&nbsp;nobody</FONT></TT> to
<TT>
<FONT COLOR="#0000ff">User&nbsp;postgres</FONT></TT>. <FONT COLOR="#ffa500">[Note that for security you should <I>really</I>
limit who can connect to the <TT>
<FONT COLOR="#0000ff">postgres</FONT></TT> database. See
Section <A HREF="node41.html#sec:instinitpostgres">38.4</A>.]</FONT>
<P>

<H2><A NAME="SECTION003929000000000000000">
36.2.9 Forms and CGI</A>
</H2>

<P>
To create a functional form, use the HTTP <TT>
<FONT COLOR="#0000ff">&lt;FORM&gt;</FONT></TT> tag as follows.
A file <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/test/form.html</FONT></TT> could contain:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;HTML&#062;</code><br>
<code>&nbsp;&nbsp;&#060;FORM&nbsp;name="myform"&nbsp;action="test.cgi"&nbsp;method="get"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&#060;TABLE&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TD&nbsp;colspan="2"&nbsp;align="center"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Please&nbsp;enter&nbsp;your&nbsp;personal&nbsp;details:</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TD&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TD&#062;Name:&#060;/TD&#062;&#060;TD&#062;&#060;INPUT&nbsp;type="text"&nbsp;name="name"&#062;&#060;/TD&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TD&#062;Email:&#060;/TD&#062;&#060;TD&#062;&#060;INPUT&nbsp;type="text"&nbsp;name="email"&#062;&#060;/TD&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TD&#062;Tel:&#060;/TD&#062;&#060;TD&#062;&#060;INPUT&nbsp;type="text"&nbsp;name="tel"&#062;&#060;/TD&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;TD&nbsp;colspan="2"&nbsp;align="center"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;INPUT&nbsp;type="submit"&nbsp;value="Submit"&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TD&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TR&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&#060;/TABLE&#062;</code><br>
<code>&nbsp;&nbsp;&#060;/FORM&#062;</code><br>
<code>&#060;/HTML&#062;</code><br>
</FONT></TD></TR></TABLE><P>
which looks like:
<DIV ALIGN="CENTER">
<!-- MATH
 $\epsfbox{form.ps}$
 -->
<IMG
 WIDTH="201" HEIGHT="192" ALIGN="BOTTOM" BORDER="0"
 SRC="img69.png"
 ALT="\epsfbox{form.ps}">
</DIV>

<P>
Note how this form calls our existing <TT>
<FONT COLOR="#0000ff">test.cgi</FONT></TT> script.
Here is a script that adds the entered data to a <TT>
<FONT COLOR="#0000ff">postgres</FONT></TT> SQL table:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>20</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>25</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>30</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#!/bin/sh</code><br>
<code>&nbsp;</code><br>
<code>echo&nbsp;'Content-type:&nbsp;text/html'</code><br>
<code>echo</code><br>
<code>&nbsp;</code><br>
<code>opts=`echo&nbsp;"$QUERY_STRING"&nbsp;|&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;sed&nbsp;-e&nbsp;'s/[^A-Za-z0-9&nbsp;%&#038;+,.\/:=@_~-]//g'&nbsp;-e&nbsp;'s/&#038;/&nbsp;/g'&nbsp;-e&nbsp;q`</code><br>
<code>&nbsp;</code><br>
<code>for&nbsp;opt&nbsp;in&nbsp;$opts&nbsp;&#059;&nbsp;do</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;case&nbsp;$opt&nbsp;in</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;name=*)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;name=${opt/name=/}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;email=*)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;email=${opt/email=/}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tel=*)</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tel=${opt/tel=/}</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&#059;&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;esac</code><br>
<code>done</code><br>
<code>&nbsp;</code><br>
<code>if&nbsp;psql&nbsp;-d&nbsp;template1&nbsp;-H&nbsp;-c&nbsp;"\</code><br>
<code>INSERT&nbsp;INTO&nbsp;people&nbsp;(name,&nbsp;email,&nbsp;tel)&nbsp;\</code><br>
<code>VALUES&nbsp;('$name',&nbsp;'$email',&nbsp;'$tel')"&nbsp;2&#062;&#038;1&nbsp;|&nbsp;grep&nbsp;-q&nbsp;'^INSERT&nbsp;'&nbsp;&#059;&nbsp;then</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;"&#060;HTML&#062;Your&nbsp;details&nbsp;\"$name\",&nbsp;\"$email\"&nbsp;and&nbsp;\"$tel\"&#060;BR&#062;"</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;"have&nbsp;been&nbsp;succesfully&nbsp;recorded.&#060;/HTML&#062;"</code><br>
<code>else</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;"&#060;HTML&#062;Database&nbsp;error,&nbsp;please&nbsp;contact&nbsp;our&nbsp;webmaster.&#060;/HTML&#062;"</code><br>
<code>fi</code><br>
<code>&nbsp;</code><br>
<code>exit&nbsp;0</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Note how the first lines of script remove all unwanted
characters from <TT>
<FONT COLOR="#0000ff">QUERY_STRING</FONT></TT>. Such processing is imperative for
security because shell scripts can easily execute commands should
characters like <TT>
<FONT COLOR="#0000ff">$</FONT></TT> and <TT>
<FONT COLOR="#0000ff">&#96;</FONT></TT> be present in a string.

<P>
To use the alternative ``POST'' method, change your <TT>
<FONT COLOR="#0000ff">FORM</FONT></TT>
tag to

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&nbsp;&nbsp;&#060;FORM&nbsp;name="myform"&nbsp;action="test.cgi"&nbsp;method="post"&#062;</code><br>
</FONT></TD></TR></TABLE><P>
The POST method sends the query text through stdin of the
CGI script. Hence, you need to also change your <TT>
<FONT COLOR="#0000ff">opts=</FONT></TT> line to

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>opts=`cat&nbsp;|&nbsp;\</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;sed&nbsp;-e&nbsp;'s/[^A-Za-z0-9&nbsp;%&#038;+,.\/:=@_~-]//g'&nbsp;-e&nbsp;'s/&#038;/&nbsp;/g'&nbsp;-e&nbsp;q`</code><br>
</FONT></TD></TR></TABLE><P>

<P>

<H2><A NAME="SECTION0039210000000000000000">
36.2.10 Setuid CGIs</A>
</H2>

<P>
<A NAME="sec:setuidcgiwrapper"></A>
<P>
Running Apache as a privileged user has security implications. Another
way to get this script to execute as user <TT>
<FONT COLOR="#0000ff">postgres</FONT></TT> is to create a
setuid binary. To do this, create a file <TT>
<FONT COLOR="#0000ff">test.cgi</FONT></TT> by compiling the
following <B>C</B> program similar to that in Section <A HREF="node36.html#sec:faxsetuidbin">33.2</A>.

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#include&nbsp;&#060;unistd.h&#062;</code><br>
<code>&nbsp;</code><br>
<code>int&nbsp;main&nbsp;(int&nbsp;argc,&nbsp;char&nbsp;*argv[])</code><br>
<code>{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;setreuid&nbsp;(geteuid&nbsp;(),&nbsp;geteuid&nbsp;())&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;execl&nbsp;("/opt/apache/htdocs/test/test.sh",&nbsp;"test.sh",&nbsp;0)&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;0&#059;</code><br>
<code>}</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Then run <TT>
<FONT COLOR="#0000ff">chown postgres:www test.cgi</FONT></TT> and
<TT>
<FONT COLOR="#0000ff">chmod a-w,o-rx,u+s test.cgi</FONT></TT> (or <TT>
<FONT COLOR="#0000ff">chmod 4550 test.cgi</FONT></TT>).
Recreate your shell script as <TT>
<FONT COLOR="#0000ff">test.sh</FONT></TT> and go to the URL again.
Apache runs <TT>
<FONT COLOR="#0000ff">test.cgi</FONT></TT>, which becomes user <TT>
<FONT COLOR="#0000ff">postgres</FONT></TT>, and then
executes the script as the <TT>
<FONT COLOR="#0000ff">postgres</FONT></TT> user. Even with Apache as
<TT>
<FONT COLOR="#0000ff">User&nbsp;nobody</FONT></TT> your script will still work. Note how your setuid
program is insecure: it takes no arguments and performs only a single
function, but it takes environment variables (or input from stdin)
that could influence its functionality. If a login user could execute
the script, that user could send data via these variables that could cause
the script to behave in an unforeseen way. An alternative is:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>#include&nbsp;&#060;unistd.h&#062;</code><br>
<code>&nbsp;</code><br>
<code>int&nbsp;main&nbsp;(int&nbsp;argc,&nbsp;char&nbsp;*argv[])</code><br>
<code>{</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;char&nbsp;*envir[]&nbsp;=&nbsp;{0}&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;setreuid&nbsp;(geteuid&nbsp;(),&nbsp;geteuid&nbsp;())&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;execle&nbsp;("/opt/apache/htdocs/test/test.sh",&nbsp;"test.sh",&nbsp;0,&nbsp;envir)&#059;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;0&#059;</code><br>
<code>}</code><br>
</FONT></TD></TR></TABLE><P>
This script nullifies the environment before starting the CGI, thus
forcing you to use the POST method only. Because the only information
that can be passed to the script is a single line of text (through the
<TT>
<FONT COLOR="#0000ff">-e&nbsp;q</FONT></TT> option to <TT>
<FONT COLOR="#0000ff">sed</FONT></TT>) and because that line of text is
carefully stripped of unwanted characters, we can be much more certain
of security.

<P>

<H2><A NAME="SECTION0039211000000000000000">
36.2.11 Apache modules and PHP</A>
</H2>

<P>
CGI execution is extremely slow if Apache has to invoke a shell
script for each hit. Apache has a number of facilities for built-in
interpreters that will parse script files with high efficiency.
A well-known programming language developed specifically for
the Web is PHP. PHP can be downloaded as source from
<EM>The PHP Home Page</EM> <I>&lt;<TT><A NAME="tex2html58"
  HREF="http://www.php.net">http://www.php.net</A></TT>&gt;</I> and contains the
usual GNU installation instructions.

<P>
Apache has the facility for adding functionality at runtime
using what it calls DSO
(<I>Dynamic Shared Object</I>) files. This feature
is for distribution vendors who want to ship split installs of Apache
that enable users to install only the parts of Apache they like. This is
conceptually the same as what we saw in Section <A HREF="node26.html#sec:sharedobj">23.1</A>: To
give your program some extra feature provided by some library, you can
<I>either</I> statically link the library to your program <I>or</I>
compile the library as a shared <TT>
<FONT COLOR="#0000ff">.so</FONT></TT> file to be linked at run
time. The difference here is that the library files are (usually) called
<TT>
<FONT COLOR="#0000ff">mod_</FONT></TT><I>name</I> and are stored in <TT>
<FONT COLOR="#0000ff">/opt/apache/libexec/</FONT></TT>.
They are also only loaded if a
<TT>
<FONT COLOR="#0000ff">LoadModule&nbsp;</FONT></TT><I>name</I><TT>
<FONT COLOR="#0000ff">_module</FONT></TT> appears in
<TT>
<FONT COLOR="#0000ff">httpd.conf</FONT></TT>. To enable DSO support, rebuild and reinstall Apache
starting with:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>./configure&nbsp;--prefix=/opt/apache&nbsp;--enable-module=so</code><br>
</FONT></TD></TR></TABLE><P>

<P>
Any source package that creates an Apache module can now use
the Apache utility <TT>
<FONT COLOR="#0000ff">/opt/apache/bin/apxs</FONT></TT> to tell it about the
current Apache installation, so you should make sure this executable
is in your <TT>
<FONT COLOR="#0000ff">PATH</FONT></TT>.

<P>
You can now follow the instructions for installing PHP,
possibly beginning with
<TT>
<FONT COLOR="#0000ff">./configure &#45;&#45;prefix=/opt/php  &#45;&#45;with-apxs=/opt/apache/bin/apxs &#45;&#45;with-pgsql=/usr</FONT></TT>. (This assumes that
you want to enable support for the <TT>
<FONT COLOR="#0000ff">postgres</FONT></TT> SQL database and have
<TT>
<FONT COLOR="#0000ff">postgres</FONT></TT> previously installed as a package under <TT>
<FONT COLOR="#0000ff">/usr</FONT></TT>.)
Finally, check that a file <TT>
<FONT COLOR="#0000ff">libphp4.so</FONT></TT> eventually ends up in
<TT>
<FONT COLOR="#0000ff">/opt/apache/libexec/</FONT></TT>.

<P>
Your <TT>
<FONT COLOR="#0000ff">httpd.conf</FONT></TT> then needs
to know about PHP scripts. Add the
following lines

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>LoadModule&nbsp;php4_module&nbsp;/opt/apache/libexec/libphp4.so</code><br>
<code>AddModule&nbsp;mod_php4.c</code><br>
<code>AddType&nbsp;application/x-httpd-php&nbsp;.php</code><br>
</FONT></TD></TR></TABLE><P>
and then create a file <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/hello.php</FONT></TT> containing

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>&#060;html&#062;</code><br>
<code>&#060;head&#062;</code><br>
<code>&#060;title&#062;Example&#060;/title&#062;</code><br>
<code>&#060;/head&#062;</code><br>
<code>&#060;body&#062;</code><br>
<code>&#060;?php&nbsp;echo&nbsp;"Hi,&nbsp;I'm&nbsp;a&nbsp;PHP&nbsp;script!"&#059;&nbsp;?&#062;</code><br>
<code>&#060;/body&#062;</code><br>
<code>&#060;/html&#062;</code><br>
</FONT></TD></TR></TABLE><P>
and test by visiting the URL <I><TT><A NAME="tex2html59"
  HREF="http://localhost/hello.php">http://localhost/hello.php</A></TT></I>.

<P>
Programming in the PHP language is beyond the scope of this book.

<P>

<H2><A NAME="SECTION0039212000000000000000">
36.2.12 Virtual hosts</A>
</H2>

<P>
Virtual hosting is the use of a single web server to serve the web pages of
multiple domains. Although the web browser seems to be connecting to
a web site that is an isolated entity, that web site may in fact be
hosted alongside many others on the same machine.

<P>
Virtual hosting is rather trivial to configure. Let us say that we have
three domains: <TT>
<FONT COLOR="#0000ff">www.domain1.com</FONT></TT>, <TT>
<FONT COLOR="#0000ff">www.domain2.com</FONT></TT>,
and <TT>
<FONT COLOR="#0000ff">www.domain3.com</FONT></TT>. We want domains <TT>
<FONT COLOR="#0000ff">www.domain1.com</FONT></TT> and
<TT>
<FONT COLOR="#0000ff">www.domain2.com</FONT></TT> to share IP address <TT>
<FONT COLOR="#0000ff">196.123.45.1</FONT></TT>, while
<TT>
<FONT COLOR="#0000ff">www.domain3.com</FONT></TT> has its own IP address of <TT>
<FONT COLOR="#0000ff">196.123.45.2</FONT></TT>.
The sharing of a single IP address is called <I>name-based virtual hosting</I>,
and
the use of a different IP address for each domain is called
<I>IP-based virtual hosting</I>.

<P>
If our machine has one IP address, <TT>
<FONT COLOR="#0000ff">196.123.45.1</FONT></TT>,
we may need to configure a separate IP address on the
same network card as follows (see Section <A HREF="node28.html#ref:interfacealiasing">25.9</A>):

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>ifconfig&nbsp;eth0:1&nbsp;196.123.45.2&nbsp;netmask&nbsp;255.255.255.0&nbsp;up</code><br>
</FONT></TD></TR></TABLE><P>
For each domain <TT>
<FONT COLOR="#0000ff">/opt/apache/htdocs/www.domain</FONT></TT><I>?</I><TT>
<FONT COLOR="#0000ff">.com/</FONT></TT>,
we now create a top-level directory.
We need to tell Apache that we intend to use the IP
address <TT>
<FONT COLOR="#0000ff">196.123.45.1</FONT></TT> for several hosts. We do that
with the <TT>
<FONT COLOR="#0000ff">NameVirtualHost</FONT></TT> directive.
Then for each host, we must specify a top-level directory as follows:

<P><TABLE nowrap="1" width="100%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top" class="source" width="2%"><FONT color=red>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>5</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>10</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<code>&nbsp;</code><br>
<font size="-1"><code>15</code></font><code>&nbsp;</code><br>
<code>&nbsp;</code><br>
</FONT></TD><TD valign="top" class="source" bgcolor="#FFE0C0"><FONT color=blue>
<code>NameVirtualHost&nbsp;196.123.45.1</code><br>
<code>&nbsp;</code><br>
<code>&#060;VirtualHost&nbsp;196.123.45.1&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;ServerName&nbsp;www.domain1.com</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;DocumentRoot&nbsp;/opt/apache/htdocs/www.domain1.com/</code><br>
<code>&#060;/VirtualHost&#062;</code><br>
<code>&nbsp;</code><br>
<code>&#060;VirtualHost&nbsp;196.123.45.1&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;ServerName&nbsp;www.domain2.com</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;DocumentRoot&nbsp;/opt/apache/htdocs/www.domain2.com/</code><br>
<code>&#060;/VirtualHost&#062;</code><br>
<code>&nbsp;</code><br>
<code>&#060;VirtualHost&nbsp;196.123.45.2&#062;</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;ServerName&nbsp;www.domain3.com</code><br>
<code>&nbsp;&nbsp;&nbsp;&nbsp;DocumentRoot&nbsp;/opt/apache/htdocs/www.domain3.com/</code><br>
<code>&#060;/VirtualHost&#062;</code><br>
</FONT></TD></TR></TABLE><P>
All that remains is to configure a correct DNS zone for each
domain so that lookups of <TT>
<FONT COLOR="#0000ff">www.domain1.com</FONT></TT> and
<TT>
<FONT COLOR="#0000ff">www.domain2.com</FONT></TT> return <TT>
<FONT COLOR="#0000ff">196.123.45.1</FONT></TT> while lookups of
<TT>
<FONT COLOR="#0000ff">www.domain3.com</FONT></TT> return <TT>
<FONT COLOR="#0000ff">196.123.45.2</FONT></TT>.

<P>
You can then add <TT>
<FONT COLOR="#0000ff">index.html</FONT></TT> files to
each directory.

<P>

<P>
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