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@ -1,20 +1,21 @@
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org">
<meta name="generator" content="HTML Tidy, see www.w3.org" />
<title>Authentication</title>
<link rev="made" href="mailto:rbowen@rcbowen.com">
<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">
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#000080" alink="#FF0000">
<!--#include virtual="header.html" -->
<h1 align="CENTER">Authentication</h1>
<a name="__index__"></a> <!-- INDEX BEGIN -->
<a id="__index__" name="__index__"></a> <!-- INDEX BEGIN -->
<ul>
@ -22,8 +23,7 @@
<li><a href="#the prerequisites">The prerequisites</a></li>
<li><a href="#getting it working">Getting it
working</a></li>
<li><a href="#getting it working">Getting it working</a></li>
<li><a href="#letting more than one person in">Letting more
than one person in</a></li>
@ -36,94 +36,99 @@
<li><a href="#more information">More information</a></li>
</ul>
<!-- INDEX END -->
<hr>
<hr />
<table border="1">
<tr>
<td valign="top"><strong>Related Modules</strong><br>
<br>
<a href="../mod/mod_auth.html">mod_auth</a><br>
<a href="../mod/mod_access.html">mod_access</a><br>
</td>
<td valign="top"><strong>Related Directives</strong><br>
<br>
<a href="../mod/mod_access.html#allow">Allow</a><br>
<a href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a><br>
<a href="../mod/core.html#authname">AuthName</a><br>
<a href="../mod/core.html#authtype">AuthType</a><br>
<a href="../mod/mod_auth.html#authuserfile">AuthUserFile</a><br>
<a href="../mod/mod_access.html#deny">Deny</a><br>
<a href="../mod/core.html#options">Options</a><br>
<a href="../mod/core.html#require">Require</a><br>
<table border="1">
<tr>
<td valign="top"><strong>Related Modules</strong><br />
<br />
<a href="../mod/mod_auth.html">mod_auth</a><br />
<a href="../mod/mod_access.html">mod_access</a><br />
</td>
</td>
</tr>
</table>
<td valign="top"><strong>Related Directives</strong><br />
<br />
<a href="../mod/mod_access.html#allow">Allow</a><br />
<a
href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a><br />
<a href="../mod/core.html#authname">AuthName</a><br />
<a href="../mod/core.html#authtype">AuthType</a><br />
<a
href="../mod/mod_auth.html#authuserfile">AuthUserFile</a><br />
<a href="../mod/mod_access.html#deny">Deny</a><br />
<a href="../mod/core.html#options">Options</a><br />
<a href="../mod/core.html#require">Require</a><br />
</td>
</tr>
</table>
<h1><a name="authentication">Authentication</a></h1>
<h1><a id="authentication"
name="authentication">Authentication</a></h1>
<p>Authentication is any process by which you verify that
someone is who they claim they are. Authorization is any
process by which someone is allowed to be where they want to
go, or to have information that they want to have.</p>
<h2><a name="introduction">Introduction</a></h2>
<h2><a id="introduction"
name="introduction">Introduction</a></h2>
<p>If you have information on your web site that is sensitive
or intended for only a small group of people, the techniques in
this article will help you make sure that the people that see
those pages are the people that you wanted to see them.</p>
<p>This article covers the "standard" way of protecting parts of your
web site that most of you are going to use.</p>
<p>This article covers the "standard" way of protecting parts
of your web site that most of you are going to use.</p>
<h2><a name="the prerequisites">The prerequisites</a></h2>
<h2><a id="the prerequisites" name="the prerequisites">The
prerequisites</a></h2>
<p>The directives discussed in this article will need to go either
in your main server configuration file (typically in a
<p>The directives discussed in this article will need to go
either in your main server configuration file (typically in a
&lt;Directory&gt; section), or in per-directory configuration
files (<code>.htaccess</code> files).</p>
<p>If you plan to use <code>.htaccess</code> files, you will need to
have a server configuration that permits putting authentication
directives in these files. This is done with the
<code><a href="../mod/core.html#allowoverride">AllowOverride</a></code>
directive, which specifies which directives, if any, may be put in
per-directory configuration files.</p>
<p>Since we're talking here about authentication, you will need an
<code>AllowOverride</code> directive like the following:</p>
<p>If you plan to use <code>.htaccess</code> files, you will
need to have a server configuration that permits putting
authentication directives in these files. This is done with the
<code><a
href="../mod/core.html#allowoverride">AllowOverride</a></code>
directive, which specifies which directives, if any, may be put
in per-directory configuration files.</p>
<p>Since we're talking here about authentication, you will need
an <code>AllowOverride</code> directive like the following:</p>
<pre>
AllowOverride AuthConfig
</pre>
<p>Or, if you are just going to put the directives directly in your
main server configuration file, you will of course need to have
write permission to that file.</p>
<p>Or, if you are just going to put the directives directly in
your main server configuration file, you will of course need to
have write permission to that file.</p>
<p>And you'll need to know a little bit about the directory
structure of your server, in order to know where some files are
kept. This should not be terribly difficult, and I'll try to
make this clear when we come to that point.</p>
<h2><a name="getting it working">Getting it working</a></h2>
<h2><a id="getting it working"
name="getting it working">Getting it working</a></h2>
<p>Here's the basics of password protecting a directory on your
server.</p>
<p>You'll need to create a password file. This file should be
placed somewhere not accessible from the web. This is so
that folks cannot download the password file. For example, if
your documents are served out of
placed somewhere not accessible from the web. This is so that
folks cannot download the password file. For example, if your
documents are served out of
<code>/usr/local/apache/htdocs</code> you might want to put the
password file(s) in <code>/usr/local/apache/passwd</code>.</p>
<p>To create the file, use the <a
href="../programs/htpasswd.html">htpasswd</a> utility that came
with Apache. This be located in the <code>bin</code> directory of
wherever you installed Apache. To create the file, type:</p>
with Apache. This be located in the <code>bin</code> directory
of wherever you installed Apache. To create the file, type:</p>
<pre>
htpasswd -c /usr/local/apache/passwd/password rbowen
</pre>
@ -142,15 +147,15 @@
On my server, it's located at
<code>/usr/local/apache/bin/htpasswd</code></p>
<p>Next, you'll need to configure the server to request a password
and tell the server which users are allowed access. You can do
this either by editing the <code>httpd.conf</code> file or using
an <code>.htaccess</code> file. For example, if you wish to
protect the directory
<p>Next, you'll need to configure the server to request a
password and tell the server which users are allowed access.
You can do this either by editing the <code>httpd.conf</code>
file or using an <code>.htaccess</code> file. For example, if
you wish to protect the directory
<code>/usr/local/apache/htdocs/secret</code>, you can use the
following directives, either placed in the file
<code>/usr/local/apache/htdocs/secret/.htaccess</code>, or placed
in httpd.conf inside a &lt;Directory
<code>/usr/local/apache/htdocs/secret/.htaccess</code>, or
placed in httpd.conf inside a &lt;Directory
/usr/local/apache/apache/htdocs/secret&gt; section.</p>
<pre>
AuthType Basic
@ -159,70 +164,73 @@
require user rbowen
</pre>
<p>Let's examine each of those directives individually. The <a
<p>Let's examine each of those directives individually. The <a
href="../mod/core.html#authtype">AuthType</a> directive selects
that method that is used to authenticate the user. The most
that method that is used to authenticate the user. The most
common method is <code>Basic</code>, and this is the method
implemented by <a href="../mod/mod_auth.html">mod_auth</a>. It is
important to be aware, however, that Basic authentication sends
the password from the client to the browser unencrypted. This
method should therefore not be used for highly sensitive data.
Apache supports one other authentication method: <code>AuthType
Digest</code>. This method is implemented by <a
href="../mod/mod_auth_digest.html">mod_auth_digest</a> and is much
more secure. Only the most recent versions of clients are known
to support Digest authentication.</p>
implemented by <a href="../mod/mod_auth.html">mod_auth</a>. It
is important to be aware, however, that Basic authentication
sends the password from the client to the browser unencrypted.
This method should therefore not be used for highly sensitive
data. Apache supports one other authentication method:
<code>AuthType Digest</code>. This method is implemented by <a
href="../mod/mod_auth_digest.html">mod_auth_digest</a> and is
much more secure. Only the most recent versions of clients are
known to support Digest authentication.</p>
<p>The <a href="../mod/core.html#authname">AuthName</a> directive
sets the <em>Realm</em> to be used in the authentication. The
realm serves two major functions. First, the client often
presents this information to the user as part of the password
dialog box. Second, it is used by the client to determine what
password to send for a given authenticated area. So, for example,
once a client has authenticated in the <code>"Restricted
Files"</code> area, it will automatically retry the same password
for any area on the same server that is marked with the
<code>"Restricted Files"</code> Realm. Therefore, you can prevent
a user from being prompted more than once for a password by
letting multiple restricted areas share the same realm. Of
course, for security reasons, the client will always need to ask
again for the password whenever the hostname of the server
changes.</p>
<p>The <a href="../mod/core.html#authname">AuthName</a>
directive sets the <em>Realm</em> to be used in the
authentication. The realm serves two major functions. First,
the client often presents this information to the user as part
of the password dialog box. Second, it is used by the client to
determine what password to send for a given authenticated area.
So, for example, once a client has authenticated in the
<code>"Restricted Files"</code> area, it will automatically
retry the same password for any area on the same server that is
marked with the <code>"Restricted Files"</code> Realm.
Therefore, you can prevent a user from being prompted more than
once for a password by letting multiple restricted areas share
the same realm. Of course, for security reasons, the client
will always need to ask again for the password whenever the
hostname of the server changes.</p>
<p>The <a
href="../mod/mod_auth.html#authuserfile">AuthUserFile</a>
directive sets the path to the password file that we just created
with <code>htpasswd</code>. If you have a large number of users,
it can be quite slow to search through a plain text file to
authenticate the user on each request. Apache also has the
ability to store user information in fast database files. The
modules <a href="../mod/mod_auth_db.html">mod_auth_db</a> and <a
href="../mod/mod_auth_dbm.html">mod_auth_dbm</a> provide the <a
directive sets the path to the password file that we just
created with <code>htpasswd</code>. If you have a large number
of users, it can be quite slow to search through a plain text
file to authenticate the user on each request. Apache also has
the ability to store user information in fast database files.
The modules <a href="../mod/mod_auth_db.html">mod_auth_db</a>
and <a href="../mod/mod_auth_dbm.html">mod_auth_dbm</a> provide
the <a
href="../mod/mod_auth_db.html#authdbuserfile">AuthDBUserFile</a>
and <a
href="../mod/mod_auth_dbm.html#authdbmuserfile">AuthDBMUserFile</a>
directives respectively. These files can be created and
directives respectively. These files can be created and
manipulated with the <a
href="../programs/dbmmanage.html">dbmmanage</a> program. Many
href="../programs/dbmmanage.html">dbmmanage</a> program. Many
other types of authentication options are available from third
party modules in the <a href="http://modules.apache.org/">Apache
Modules Database</a>.</p>
party modules in the <a
href="http://modules.apache.org/">Apache Modules
Database</a>.</p>
<p>Finally, the <a href="../mod/core.html#require">require</a>
directive provides the authorization part of the process by
setting the user that is allowed to access this region of the
server. In the next section, we discuss various ways to
use the <code>require</code> directive.</p>
server. In the next section, we discuss various ways to use the
<code>require</code> directive.</p>
<h2><a name="letting more than one person in">Letting more than
one person in</a></h2>
<h2><a id="letting more than one person in"
name="letting more than one person in">Letting more than one
person in</a></h2>
<p>The directives above only let one person (specifically someone
with a username of <code>rbowen</code>) into the directory. In
most cases, you'll want to let more than one person in. This is
where the <a
href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a> comes
in.</p>
<p>The directives above only let one person (specifically
someone with a username of <code>rbowen</code>) into the
directory. In most cases, you'll want to let more than one
person in. This is where the <a
href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a>
comes in.</p>
<p>If you want to let more than one person in, you'll need to
create a group file that associates group names with a list of
@ -279,7 +287,8 @@
files, and remember to reference th right one in the
<code>AuthUserFile</code> directive.</p>
<h2><a name="possible problems">Possible problems</a></h2>
<h2><a id="possible problems" name="possible problems">Possible
problems</a></h2>
<p>Because of the way that Basic authentication is specified,
your username and password must be verified every time you
@ -292,15 +301,16 @@
until it gets to your name. And it has to do this every time a
page is loaded.</p>
<p>A consequence of this is that there's a practical limit to how many
users you can put in one password file. This limit will vary
depending on the performance of your particular server machine, but
you can expect to see slowdowns once you get above a few hundred
entries, and may wish to consider a different authentication method
at that time.</p>
<p>A consequence of this is that there's a practical limit to
how many users you can put in one password file. This limit
will vary depending on the performance of your particular
server machine, but you can expect to see slowdowns once you
get above a few hundred entries, and may wish to consider a
different authentication method at that time.</p>
<h2><a name="what other neat stuff can i do">What other neat
stuff can I do?</a></h2>
<h2><a id="what other neat stuff can i do"
name="what other neat stuff can i do">What other neat stuff can
I do?</a></h2>
<p>Authentication by username and password is only part of the
story. Frequently you want to let people in based on something
@ -360,12 +370,13 @@
addition to letting everyone in. What you want is to let
<em>only</em> those folks in.</p>
<h2><a name="more information">More information</a></h2>
<h2><a id="more information" name="more information">More
information</a></h2>
<p>You should also read the documentation for
<code><a href="../mod/mod_auth.html">mod_auth</a></code> and
<code><a href="../mod/mod_access.html">mod_access</a></code>
which contain some more information about how this all works.</p>
<p>You should also read the documentation for <code><a
href="../mod/mod_auth.html">mod_auth</a></code> and <code><a
href="../mod/mod_access.html">mod_access</a></code> which
contain some more information about how this all works.</p>
</body>
</html>

259
docs/manual/howto/auth.html.en
View File

@ -1,20 +1,21 @@
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org">
<meta name="generator" content="HTML Tidy, see www.w3.org" />
<title>Authentication</title>
<link rev="made" href="mailto:rbowen@rcbowen.com">
<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">
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#000080" alink="#FF0000">
<!--#include virtual="header.html" -->
<h1 align="CENTER">Authentication</h1>
<a name="__index__"></a> <!-- INDEX BEGIN -->
<a id="__index__" name="__index__"></a> <!-- INDEX BEGIN -->
<ul>
@ -22,8 +23,7 @@
<li><a href="#the prerequisites">The prerequisites</a></li>
<li><a href="#getting it working">Getting it
working</a></li>
<li><a href="#getting it working">Getting it working</a></li>
<li><a href="#letting more than one person in">Letting more
than one person in</a></li>
@ -36,94 +36,99 @@
<li><a href="#more information">More information</a></li>
</ul>
<!-- INDEX END -->
<hr>
<hr />
<table border="1">
<tr>
<td valign="top"><strong>Related Modules</strong><br>
<br>
<a href="../mod/mod_auth.html">mod_auth</a><br>
<a href="../mod/mod_access.html">mod_access</a><br>
</td>
<td valign="top"><strong>Related Directives</strong><br>
<br>
<a href="../mod/mod_access.html#allow">Allow</a><br>
<a href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a><br>
<a href="../mod/core.html#authname">AuthName</a><br>
<a href="../mod/core.html#authtype">AuthType</a><br>
<a href="../mod/mod_auth.html#authuserfile">AuthUserFile</a><br>
<a href="../mod/mod_access.html#deny">Deny</a><br>
<a href="../mod/core.html#options">Options</a><br>
<a href="../mod/core.html#require">Require</a><br>
<table border="1">
<tr>
<td valign="top"><strong>Related Modules</strong><br />
<br />
<a href="../mod/mod_auth.html">mod_auth</a><br />
<a href="../mod/mod_access.html">mod_access</a><br />
</td>
</td>
</tr>
</table>
<td valign="top"><strong>Related Directives</strong><br />
<br />
<a href="../mod/mod_access.html#allow">Allow</a><br />
<a
href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a><br />
<a href="../mod/core.html#authname">AuthName</a><br />
<a href="../mod/core.html#authtype">AuthType</a><br />
<a
href="../mod/mod_auth.html#authuserfile">AuthUserFile</a><br />
<a href="../mod/mod_access.html#deny">Deny</a><br />
<a href="../mod/core.html#options">Options</a><br />
<a href="../mod/core.html#require">Require</a><br />
</td>
</tr>
</table>
<h1><a name="authentication">Authentication</a></h1>
<h1><a id="authentication"
name="authentication">Authentication</a></h1>
<p>Authentication is any process by which you verify that
someone is who they claim they are. Authorization is any
process by which someone is allowed to be where they want to
go, or to have information that they want to have.</p>
<h2><a name="introduction">Introduction</a></h2>
<h2><a id="introduction"
name="introduction">Introduction</a></h2>
<p>If you have information on your web site that is sensitive
or intended for only a small group of people, the techniques in
this article will help you make sure that the people that see
those pages are the people that you wanted to see them.</p>
<p>This article covers the "standard" way of protecting parts of your
web site that most of you are going to use.</p>
<p>This article covers the "standard" way of protecting parts
of your web site that most of you are going to use.</p>
<h2><a name="the prerequisites">The prerequisites</a></h2>
<h2><a id="the prerequisites" name="the prerequisites">The
prerequisites</a></h2>
<p>The directives discussed in this article will need to go either
in your main server configuration file (typically in a
<p>The directives discussed in this article will need to go
either in your main server configuration file (typically in a
&lt;Directory&gt; section), or in per-directory configuration
files (<code>.htaccess</code> files).</p>
<p>If you plan to use <code>.htaccess</code> files, you will need to
have a server configuration that permits putting authentication
directives in these files. This is done with the
<code><a href="../mod/core.html#allowoverride">AllowOverride</a></code>
directive, which specifies which directives, if any, may be put in
per-directory configuration files.</p>
<p>Since we're talking here about authentication, you will need an
<code>AllowOverride</code> directive like the following:</p>
<p>If you plan to use <code>.htaccess</code> files, you will
need to have a server configuration that permits putting
authentication directives in these files. This is done with the
<code><a
href="../mod/core.html#allowoverride">AllowOverride</a></code>
directive, which specifies which directives, if any, may be put
in per-directory configuration files.</p>
<p>Since we're talking here about authentication, you will need
an <code>AllowOverride</code> directive like the following:</p>
<pre>
AllowOverride AuthConfig
</pre>
<p>Or, if you are just going to put the directives directly in your
main server configuration file, you will of course need to have
write permission to that file.</p>
<p>Or, if you are just going to put the directives directly in
your main server configuration file, you will of course need to
have write permission to that file.</p>
<p>And you'll need to know a little bit about the directory
structure of your server, in order to know where some files are
kept. This should not be terribly difficult, and I'll try to
make this clear when we come to that point.</p>
<h2><a name="getting it working">Getting it working</a></h2>
<h2><a id="getting it working"
name="getting it working">Getting it working</a></h2>
<p>Here's the basics of password protecting a directory on your
server.</p>
<p>You'll need to create a password file. This file should be
placed somewhere not accessible from the web. This is so
that folks cannot download the password file. For example, if
your documents are served out of
placed somewhere not accessible from the web. This is so that
folks cannot download the password file. For example, if your
documents are served out of
<code>/usr/local/apache/htdocs</code> you might want to put the
password file(s) in <code>/usr/local/apache/passwd</code>.</p>
<p>To create the file, use the <a
href="../programs/htpasswd.html">htpasswd</a> utility that came
with Apache. This be located in the <code>bin</code> directory of
wherever you installed Apache. To create the file, type:</p>
with Apache. This be located in the <code>bin</code> directory
of wherever you installed Apache. To create the file, type:</p>
<pre>
htpasswd -c /usr/local/apache/passwd/password rbowen
</pre>
@ -142,15 +147,15 @@
On my server, it's located at
<code>/usr/local/apache/bin/htpasswd</code></p>
<p>Next, you'll need to configure the server to request a password
and tell the server which users are allowed access. You can do
this either by editing the <code>httpd.conf</code> file or using
an <code>.htaccess</code> file. For example, if you wish to
protect the directory
<p>Next, you'll need to configure the server to request a
password and tell the server which users are allowed access.
You can do this either by editing the <code>httpd.conf</code>
file or using an <code>.htaccess</code> file. For example, if
you wish to protect the directory
<code>/usr/local/apache/htdocs/secret</code>, you can use the
following directives, either placed in the file
<code>/usr/local/apache/htdocs/secret/.htaccess</code>, or placed
in httpd.conf inside a &lt;Directory
<code>/usr/local/apache/htdocs/secret/.htaccess</code>, or
placed in httpd.conf inside a &lt;Directory
/usr/local/apache/apache/htdocs/secret&gt; section.</p>
<pre>
AuthType Basic
@ -159,70 +164,73 @@
require user rbowen
</pre>
<p>Let's examine each of those directives individually. The <a
<p>Let's examine each of those directives individually. The <a
href="../mod/core.html#authtype">AuthType</a> directive selects
that method that is used to authenticate the user. The most
that method that is used to authenticate the user. The most
common method is <code>Basic</code>, and this is the method
implemented by <a href="../mod/mod_auth.html">mod_auth</a>. It is
important to be aware, however, that Basic authentication sends
the password from the client to the browser unencrypted. This
method should therefore not be used for highly sensitive data.
Apache supports one other authentication method: <code>AuthType
Digest</code>. This method is implemented by <a
href="../mod/mod_auth_digest.html">mod_auth_digest</a> and is much
more secure. Only the most recent versions of clients are known
to support Digest authentication.</p>
implemented by <a href="../mod/mod_auth.html">mod_auth</a>. It
is important to be aware, however, that Basic authentication
sends the password from the client to the browser unencrypted.
This method should therefore not be used for highly sensitive
data. Apache supports one other authentication method:
<code>AuthType Digest</code>. This method is implemented by <a
href="../mod/mod_auth_digest.html">mod_auth_digest</a> and is
much more secure. Only the most recent versions of clients are
known to support Digest authentication.</p>
<p>The <a href="../mod/core.html#authname">AuthName</a> directive
sets the <em>Realm</em> to be used in the authentication. The
realm serves two major functions. First, the client often
presents this information to the user as part of the password
dialog box. Second, it is used by the client to determine what
password to send for a given authenticated area. So, for example,
once a client has authenticated in the <code>"Restricted
Files"</code> area, it will automatically retry the same password
for any area on the same server that is marked with the
<code>"Restricted Files"</code> Realm. Therefore, you can prevent
a user from being prompted more than once for a password by
letting multiple restricted areas share the same realm. Of
course, for security reasons, the client will always need to ask
again for the password whenever the hostname of the server
changes.</p>
<p>The <a href="../mod/core.html#authname">AuthName</a>
directive sets the <em>Realm</em> to be used in the
authentication. The realm serves two major functions. First,
the client often presents this information to the user as part
of the password dialog box. Second, it is used by the client to
determine what password to send for a given authenticated area.
So, for example, once a client has authenticated in the
<code>"Restricted Files"</code> area, it will automatically
retry the same password for any area on the same server that is
marked with the <code>"Restricted Files"</code> Realm.
Therefore, you can prevent a user from being prompted more than
once for a password by letting multiple restricted areas share
the same realm. Of course, for security reasons, the client
will always need to ask again for the password whenever the
hostname of the server changes.</p>
<p>The <a
href="../mod/mod_auth.html#authuserfile">AuthUserFile</a>
directive sets the path to the password file that we just created
with <code>htpasswd</code>. If you have a large number of users,
it can be quite slow to search through a plain text file to
authenticate the user on each request. Apache also has the
ability to store user information in fast database files. The
modules <a href="../mod/mod_auth_db.html">mod_auth_db</a> and <a
href="../mod/mod_auth_dbm.html">mod_auth_dbm</a> provide the <a
directive sets the path to the password file that we just
created with <code>htpasswd</code>. If you have a large number
of users, it can be quite slow to search through a plain text
file to authenticate the user on each request. Apache also has
the ability to store user information in fast database files.
The modules <a href="../mod/mod_auth_db.html">mod_auth_db</a>
and <a href="../mod/mod_auth_dbm.html">mod_auth_dbm</a> provide
the <a
href="../mod/mod_auth_db.html#authdbuserfile">AuthDBUserFile</a>
and <a
href="../mod/mod_auth_dbm.html#authdbmuserfile">AuthDBMUserFile</a>
directives respectively. These files can be created and
directives respectively. These files can be created and
manipulated with the <a
href="../programs/dbmmanage.html">dbmmanage</a> program. Many
href="../programs/dbmmanage.html">dbmmanage</a> program. Many
other types of authentication options are available from third
party modules in the <a href="http://modules.apache.org/">Apache
Modules Database</a>.</p>
party modules in the <a
href="http://modules.apache.org/">Apache Modules
Database</a>.</p>
<p>Finally, the <a href="../mod/core.html#require">require</a>
directive provides the authorization part of the process by
setting the user that is allowed to access this region of the
server. In the next section, we discuss various ways to
use the <code>require</code> directive.</p>
server. In the next section, we discuss various ways to use the
<code>require</code> directive.</p>
<h2><a name="letting more than one person in">Letting more than
one person in</a></h2>
<h2><a id="letting more than one person in"
name="letting more than one person in">Letting more than one
person in</a></h2>
<p>The directives above only let one person (specifically someone
with a username of <code>rbowen</code>) into the directory. In
most cases, you'll want to let more than one person in. This is
where the <a
href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a> comes
in.</p>
<p>The directives above only let one person (specifically
someone with a username of <code>rbowen</code>) into the
directory. In most cases, you'll want to let more than one
person in. This is where the <a
href="../mod/mod_auth.html#authgroupfile">AuthGroupFile</a>
comes in.</p>
<p>If you want to let more than one person in, you'll need to
create a group file that associates group names with a list of
@ -279,7 +287,8 @@
files, and remember to reference th right one in the
<code>AuthUserFile</code> directive.</p>
<h2><a name="possible problems">Possible problems</a></h2>
<h2><a id="possible problems" name="possible problems">Possible
problems</a></h2>
<p>Because of the way that Basic authentication is specified,
your username and password must be verified every time you
@ -292,15 +301,16 @@
until it gets to your name. And it has to do this every time a
page is loaded.</p>
<p>A consequence of this is that there's a practical limit to how many
users you can put in one password file. This limit will vary
depending on the performance of your particular server machine, but
you can expect to see slowdowns once you get above a few hundred
entries, and may wish to consider a different authentication method
at that time.</p>
<p>A consequence of this is that there's a practical limit to
how many users you can put in one password file. This limit
will vary depending on the performance of your particular
server machine, but you can expect to see slowdowns once you
get above a few hundred entries, and may wish to consider a
different authentication method at that time.</p>
<h2><a name="what other neat stuff can i do">What other neat
stuff can I do?</a></h2>
<h2><a id="what other neat stuff can i do"
name="what other neat stuff can i do">What other neat stuff can
I do?</a></h2>
<p>Authentication by username and password is only part of the
story. Frequently you want to let people in based on something
@ -360,12 +370,13 @@
addition to letting everyone in. What you want is to let
<em>only</em> those folks in.</p>
<h2><a name="more information">More information</a></h2>
<h2><a id="more information" name="more information">More
information</a></h2>
<p>You should also read the documentation for
<code><a href="../mod/mod_auth.html">mod_auth</a></code> and
<code><a href="../mod/mod_access.html">mod_access</a></code>
which contain some more information about how this all works.</p>
<p>You should also read the documentation for <code><a
href="../mod/mod_auth.html">mod_auth</a></code> and <code><a
href="../mod/mod_access.html">mod_access</a></code> which
contain some more information about how this all works.</p>
</body>
</html>

769
docs/manual/howto/cgi.html.en
View File

@ -1,405 +1,454 @@
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<head>
<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>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<a name="__index__"></a> <!-- INDEX BEGIN -->
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org" />
<ul>
<li><a href="#dynamiccontentwithcgi">Dynamic Content with
CGI</a></li>
<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) -->
<li><a href="#configuringapachetopermitcgi">Configuring Apache to
permit CGI</a>
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#000080" alink="#FF0000">
<!--#include virtual="header.html" -->
<ul>
<li><a href="#scriptalias">ScriptAlias</a></li>
<h1 align="CENTER">Dynamic Content with CGI</h1>
<a id="__index__" name="__index__"></a> <!-- INDEX BEGIN -->
<li><a href="#cgioutsideofscriptaliasdirectories">CGI outside of
ScriptAlias directories</a>
<ul>
<li><a href="#dynamiccontentwithcgi">Dynamic Content with
CGI</a></li>
<ul>
<li><a href="#explicitlyusingoptionstopermitcgiexecution">Explicitly using
Options to permit CGI execution</a></li>
<li>
<a href="#configuringapachetopermitcgi">Configuring Apache
to permit CGI</a>
<li><a href="#htaccessfiles">.htaccess files</a></li>
</ul>
</li>
</ul>
</li>
<ul>
<li><a href="#scriptalias">ScriptAlias</a></li>
<li><a href="#writingacgiprogram">Writing a CGI program</a>
<li>
<a href="#cgioutsideofscriptaliasdirectories">CGI
outside of ScriptAlias directories</a>
<ul>
<li><a href="#yourfirstcgiprogram">Your first CGI program</a></li>
</ul>
</li>
<ul>
<li><a
href="#explicitlyusingoptionstopermitcgiexecution">Explicitly
using Options to permit CGI execution</a></li>
<li><a href="#butitsstillnotworking">But it's still not
working!</a>
<li><a href="#htaccessfiles">.htaccess files</a></li>
</ul>
</li>
</ul>
</li>
<ul>
<li><a href="#filepermissions">File permissions</a></li>
<li>
<a href="#writingacgiprogram">Writing a CGI program</a>
<li><a href="#pathinformation">Path information</a></li>
<ul>
<li><a href="#yourfirstcgiprogram">Your first CGI
program</a></li>
</ul>
</li>
<li><a href="#syntaxerrors">Syntax errors</a></li>
<li>
<a href="#butitsstillnotworking">But it's still not
working!</a>
<li><a href="#errorlogs">Error logs</a></li>
</ul>
</li>
<ul>
<li><a href="#filepermissions">File permissions</a></li>
<li><a href="#whatsgoingonbehindthescenes">What's going on behind
the scenes?</a>
<li><a href="#pathinformation">Path information</a></li>
<ul>
<li><a href="#environmentvariables">Environment variables</a></li>
<li><a href="#syntaxerrors">Syntax errors</a></li>
<li><a href="#stdinandstdout">STDIN and STDOUT</a></li>
</ul>
</li>
<li><a href="#errorlogs">Error logs</a></li>
</ul>
</li>
<li><a href="#cgimoduleslibraries">CGI modules/libraries</a></li>
<li>
<a href="#whatsgoingonbehindthescenes">What's going on
behind the scenes?</a>
<li><a href="#formoreinformation">For more information</a></li>
</ul>
<ul>
<li><a href="#environmentvariables">Environment
variables</a></li>
<!-- INDEX END -->
<hr>
<h2><a name="dynamiccontentwithcgi">Dynamic Content with
CGI</a></h2>
<li><a href="#stdinandstdout">STDIN and STDOUT</a></li>
</ul>
</li>
<table border="1">
<tr><td valign="top">
<strong>Related Modules</strong><br><br>
<li><a href="#cgimoduleslibraries">CGI
modules/libraries</a></li>
<a href="../mod/mod_alias.html">mod_alias</a><br>
<a href="../mod/mod_cgi.html">mod_cgi</a><br>
<li><a href="#formoreinformation">For more
information</a></li>
</ul>
<!-- INDEX END -->
<hr />
</td><td valign="top">
<strong>Related Directives</strong><br><br>
<h2><a id="dynamiccontentwithcgi"
name="dynamiccontentwithcgi">Dynamic Content with CGI</a></h2>
<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>
<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></tr></table>
<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>
<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 />
<hr>
<h2><a name="configuringapachetopermitcgi">Configuring Apache to
permit CGI</a></h2>
<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>
<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 name="scriptalias">ScriptAlias</a></h3>
<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>
<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>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>
<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 name="cgioutsideofscriptaliasdirectories">CGI outside of
ScriptAlias directories</a></h3>
<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>
<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 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>
<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>
&lt;Directory /usr/local/apache/htdocs/somedir&gt;
Options +ExecCGI
&lt;/Directory&gt;
</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>
<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 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>
<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>
<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>
<p>which tells Apache that execution of CGI programs is
permitted in this directory.</p>
<hr />
<hr>
<h2><a name="writingacgiprogram">Writing a CGI program</a></h2>
<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>
<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>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>
<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 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>
<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>
<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>
<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 />
<hr>
<h2><a name="butitsstillnotworking">But it's still not
working!</a></h2>
<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>
<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>
<dl>
<dt>The output of your CGI program</dt>
<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>
<dd>Great! That means everything worked fine.<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>The source code of your CGI program or a "POST Method Not
Allowed" message</dt>
<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>
<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>
<h3><a name="filepermissions">File permissions</a></h3>
<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>
<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>
<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>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>
<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 name="pathinformation">Path information</a></h3>
<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 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>
<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>
<p>Make sure that this is in fact the path to the
interpreter.</p>
<h3><a name="syntaxerrors">Syntax errors</a></h3>
<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>
<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 name="errorlogs">Error logs</a></h3>
<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>
<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 />
<hr>
<h2><a name="whatsgoingonbehindthescenes">What's going on behind
the scenes?</a></h2>
<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>
<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 name="environmentvariables">Environment variables</a></h3>
<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>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>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>
<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";
@ -408,92 +457,96 @@ the basic ones provided by default.</p>
}
</pre>
<h3><a name="stdinandstdout">STDIN and STDOUT</a></h3>
<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>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 (&amp;). 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>
<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 (&amp;).
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&amp;city=Lexington&amp;state=KY&amp;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>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>
<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 />
<hr>
<h2><a name="cgimoduleslibraries">CGI modules/libraries</a></h2>
<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>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 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>
<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 />
<hr>
<h2><a name="formoreinformation">For more information</a></h2>
<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>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>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>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>
<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>

23
docs/manual/howto/footer.html
View File

@ -1,8 +1,19 @@
<HR>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<H3 ALIGN="CENTER">
Apache HTTP Server Version 2.0
</H3>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org" />
<title></title>
</head>
<body>
<hr />
<h3 align="CENTER">Apache HTTP Server Version 2.0</h3>
<a href="./"><img src="../images/index.gif" alt="Index" /></a>
<a href="../"><img src="../images/home.gif" alt="Home" /></a>
</body>
</html>
<A HREF="./"><IMG SRC="../images/index.gif" ALT="Index"></A>
<A HREF="../"><IMG SRC="../images/home.gif" ALT="Home"></A>

25
docs/manual/howto/header.html
View File

@ -1,6 +1,19 @@
<DIV ALIGN="CENTER">
<IMG SRC="../images/sub.gif" ALT="[APACHE DOCUMENTATION]">
<H3>
Apache HTTP Server Version 2.0
</H3>
</DIV>
<!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></title>
</head>
<body>
<div align="CENTER">
<img src="../images/sub.gif" alt="[APACHE DOCUMENTATION]" />
<h3>Apache HTTP Server Version 2.0</h3>
</div>
</body>
</html>

707
docs/manual/howto/ssi.html.en
View File

@ -1,142 +1,159 @@
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<head>
<title>Apache Tutorial: Introduction to Server Side Includes</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">Apache Tutorial: Introduction to Server Side
Includes</h1>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<a name="__index__"></a> <!-- INDEX BEGIN -->
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="generator" content="HTML Tidy, see www.w3.org" />
<ul>
<li><a href=
"#apachetutorial:introductiontoserversideincludes">Apache
Tutorial: Introduction to Server Side Includes</a></li>
<title>Apache Tutorial: Introduction to Server Side
Includes</title>
<link rev="made" href="mailto:rbowen@rcbowen.com" />
</head>
<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
<li><a href="#whataressi">What are SSI?</a></li>
<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
vlink="#000080" alink="#FF0000">
<!--#include virtual="header.html" -->
<li><a href="#configuringyourservertopermitssi">Configuring your
server to permit SSI</a></li>
<h1 align="CENTER">Apache Tutorial: Introduction to Server Side
Includes</h1>
<a id="__index__" name="__index__"></a> <!-- INDEX BEGIN -->
<li><a href="#basicssidirectives">Basic SSI directives</a>
<ul>
<li><a
href="#apachetutorial:introductiontoserversideincludes">Apache
Tutorial: Introduction to Server Side Includes</a></li>
<ul>
<li><a href="#today'sdate">Today's date</a></li>
<li><a href="#whataressi">What are SSI?</a></li>
<li><a href="#modificationdateofthefile">Modification date of the
file</a></li>
<li><a href="#configuringyourservertopermitssi">Configuring
your server to permit SSI</a></li>
<li><a href="#includingtheresultsofacgiprogram">Including the
results of a CGI program</a></li>
</ul>
</li>
<li>
<a href="#basicssidirectives">Basic SSI directives</a>
<li><a href="#additionalexamples">Additional examples</a>
<ul>
<li><a href="#today'sdate">Today's date</a></li>
<ul>
<li><a href="#whenwasthisdocumentmodified">When was this document
modified?</a></li>
<li><a href="#modificationdateofthefile">Modification
date of the file</a></li>
<li><a href="#includingastandardfooter">Including a standard
footer</a></li>
<li><a href="#includingtheresultsofacgiprogram">Including
the results of a CGI program</a></li>
</ul>
</li>
<li><a href="#whatelsecaniconfig">What else can I config?</a></li>
<li>
<a href="#additionalexamples">Additional examples</a>
<li><a href="#executingcommands">Executing commands</a></li>
</ul>
</li>
<ul>
<li><a href="#whenwasthisdocumentmodified">When was this
document modified?</a></li>
<li><a href="#advancedssitechniques">Advanced SSI techniques</a>
<li><a href="#includingastandardfooter">Including a
standard footer</a></li>
<ul>
<li><a href="#settingvariables">Setting variables</a></li>
<li><a href="#whatelsecaniconfig">What else can I
config?</a></li>
<li><a href="#conditionalexpressions">Conditional expressions</a></li>
</ul>
</li>
<li><a href="#executingcommands">Executing
commands</a></li>
</ul>
</li>
<li><a href="#conclusion">Conclusion</a></li>
</ul>
<li>
<a href="#advancedssitechniques">Advanced SSI
techniques</a>
<!-- INDEX END -->
<hr>
<h2><a name=
"apachetutorial:introductiontoserversideincludes">Apache
Tutorial: Introduction to Server Side Includes</a></h2>
<ul>
<li><a href="#settingvariables">Setting
variables</a></li>
<table border="1">
<tr>
<td valign="top"><strong>Related Modules</strong><br>
<br>
<a href="../mod/mod_include.html">mod_include</a><br>
<a href="../mod/mod_cgi.html">mod_cgi</a><br>
<a href="../mod/mod_expires.html">mod_expires</a><br>
</td>
<td valign="top"><strong>Related Directives</strong><br>
<br>
<a href="../mod/core.html#options">Options</a><br>
<a href="../mod/mod_include.html#xbithack">XBitHack</a><br>
<a href="../mod/mod_mime.html#addtype">AddType</a><br>
<a href="../mod/core.html.html#setoutputfilter">SetOutputFilter</a><br>
<a href=
"../mod/mod_setenvif.html#BrowserMatchNoCase">BrowserMatchNoCase</a><br>
<li><a href="#conditionalexpressions">Conditional
expressions</a></li>
</ul>
</li>
</td>
</tr>
</table>
<li><a href="#conclusion">Conclusion</a></li>
</ul>
<!-- INDEX END -->
<hr />
<p>This article deals with Server Side Includes, usually called simply
SSI. In this article, I'll talk about configuring your server to permit
SSI, and introduce some basic SSI techniques for adding dynamic content
to your existing HTML pages.</p>
<h2><a id="apachetutorial:introductiontoserversideincludes"
name="apachetutorial:introductiontoserversideincludes">Apache
Tutorial: Introduction to Server Side Includes</a></h2>
<p>In the latter part of the article, we'll talk about some of the
somewhat more advanced things that can be done with SSI, such as
conditional statements in your SSI directives.</p>
<table border="1">
<tr>
<td valign="top"><strong>Related Modules</strong><br />
<br />
<a href="../mod/mod_include.html">mod_include</a><br />
<a href="../mod/mod_cgi.html">mod_cgi</a><br />
<a href="../mod/mod_expires.html">mod_expires</a><br />
</td>
<hr>
<h2><a name="whataressi">What are SSI?</a></h2>
<td valign="top"><strong>Related Directives</strong><br />
<br />
<a href="../mod/core.html#options">Options</a><br />
<a
href="../mod/mod_include.html#xbithack">XBitHack</a><br />
<a href="../mod/mod_mime.html#addtype">AddType</a><br />
<a
href="../mod/core.html.html#setoutputfilter">SetOutputFilter</a><br />
<a
href="../mod/mod_setenvif.html#BrowserMatchNoCase">BrowserMatchNoCase</a><br />
</td>
</tr>
</table>
<p>SSI (Server Side Includes) are directives that are placed in HTML
pages, and evaluated on the server while the pages are being served.
They let you add dynamically generated content to an existing HTML
page, without having to serve the entire page via a CGI program, or
other dynamic technology.</p>
<p>This article deals with Server Side Includes, usually called
simply SSI. In this article, I'll talk about configuring your
server to permit SSI, and introduce some basic SSI techniques
for adding dynamic content to your existing HTML pages.</p>
<p>The decision of when to use SSI, and when to have your page entirely
generated by some program, is usually a matter of how much of the page
is static, and how much needs to be recalculated every time the page is
served. SSI is a great way to add small pieces of information, such as
the current time. But if a majority of your page is being generated at
the time that it is served, you need to look for some other
solution.</p>
<p>In the latter part of the article, we'll talk about some of
the somewhat more advanced things that can be done with SSI,
such as conditional statements in your SSI directives.</p>
<hr />
<hr>
<h2><a name="configuringyourservertopermitssi">Configuring your
server to permit SSI</a></h2>
<h2><a id="whataressi" name="whataressi">What are SSI?</a></h2>
<p>To permit SSI on your server, you must have the following directive
either in your <code>httpd.conf</code> file, or in a
<code>.htaccess</code> file:</p>
<p>SSI (Server Side Includes) are directives that are placed in
HTML pages, and evaluated on the server while the pages are
being served. They let you add dynamically generated content to
an existing HTML page, without having to serve the entire page
via a CGI program, or other dynamic technology.</p>
<p>The decision of when to use SSI, and when to have your page
entirely generated by some program, is usually a matter of how
much of the page is static, and how much needs to be
recalculated every time the page is served. SSI is a great way
to add small pieces of information, such as the current time.
But if a majority of your page is being generated at the time
that it is served, you need to look for some other
solution.</p>
<hr />
<h2><a id="configuringyourservertopermitssi"
name="configuringyourservertopermitssi">Configuring your server
to permit SSI</a></h2>
<p>To permit SSI on your server, you must have the following
directive either in your <code>httpd.conf</code> file, or in a
<code>.htaccess</code> file:</p>
<pre>
Options +Includes
</pre>
<p>This tells Apache that you want to permit files to be parsed for SSI
directives.</p>
<p>Not just any file is parsed for SSI directives. You have to tell
Apache which files should be parsed. There are two ways to do this. You
can tell Apache to parse any file with a particular file extension,
such as <code>.shtml</code>, with the following directives:</p>
<p>This tells Apache that you want to permit files to be parsed
for SSI directives.</p>
<p>Not just any file is parsed for SSI directives. You have to
tell Apache which files should be parsed. There are two ways to
do this. You can tell Apache to parse any file with a
particular file extension, such as <code>.shtml</code>, with
the following directives:</p>
<pre>
AddType text/html .shtml
&lt;FilesMatch "\.shtml(\..+)?$"&gt;
@ -144,321 +161,330 @@ such as <code>.shtml</code>, with the following directives:</p>
&lt;/FilesMatch&gt;
</pre>
<p>One disadvantage to this approach is that if you wanted to add SSI
directives to an existing page, you would have to change the name of
that page, and all links to that page, in order to give it a
<code>.shtml</code> extension, so that those directives would be
executed.</p>
<p>The other method is to use the <code>XBitHack</code> directive:</p>
<p>One disadvantage to this approach is that if you wanted to
add SSI directives to an existing page, you would have to
change the name of that page, and all links to that page, in
order to give it a <code>.shtml</code> extension, so that those
directives would be executed.</p>
<p>The other method is to use the <code>XBitHack</code>
directive:</p>
<pre>
XBitHack on
</pre>
<p><code>XBitHack</code> tells Apache to parse files for SSI directives
if they have the execute bit set. So, to add SSI directives to an
existing page, rather than having to change the file name, you would
just need to make the file executable using <code>chmod</code>.</p>
<p><code>XBitHack</code> tells Apache to parse files for SSI
directives if they have the execute bit set. So, to add SSI
directives to an existing page, rather than having to change
the file name, you would just need to make the file executable
using <code>chmod</code>.</p>
<pre>
chmod +x pagename.html
</pre>
<p>A brief comment about what not to do. You'll occasionally see people
recommending that you just tell Apache to parse all <code>.html</code>
files for SSI, so that you don't have to mess with <code>.shtml</code>
file names. These folks have perhaps not heard about
<code>XBitHack</code>. The thing to keep in mind is that, by doing
this, you're requiring that Apache read through every single file that
it sends out to clients, even if they don't contain any SSI directives.
This can slow things down quite a bit, and is not a good idea.</p>
<p>A brief comment about what not to do. You'll occasionally
see people recommending that you just tell Apache to parse all
<code>.html</code> files for SSI, so that you don't have to
mess with <code>.shtml</code> file names. These folks have
perhaps not heard about <code>XBitHack</code>. The thing to
keep in mind is that, by doing this, you're requiring that
Apache read through every single file that it sends out to
clients, even if they don't contain any SSI directives. This
can slow things down quite a bit, and is not a good idea.</p>
<p>Of course, on Windows, there is no such thing as an execute bit to
set, so that limits your options a little.</p>
<p>Of course, on Windows, there is no such thing as an execute
bit to set, so that limits your options a little.</p>
<p>In its default configuration, Apache does not send the last modified
date or content length HTTP headers on SSI pages, because these values are
difficult to calculate for dynamic content. This can prevent your
document from being cached, and result in slower perceived client
performance. There are two ways to solve this:</p>
<p>In its default configuration, Apache does not send the last
modified date or content length HTTP headers on SSI pages,
because these values are difficult to calculate for dynamic
content. This can prevent your document from being cached, and
result in slower perceived client performance. There are two
ways to solve this:</p>
<ol>
<ol>
<li>Use the <code>XBitHack Full</code> configuration. This
tells Apache to determine the last modified date by looking
only at the date of the originally requested file, ignoring
the modification date of any included files.</li>
<li>Use the <code>XBitHack Full</code> configuration. This tells
Apache to determine the last modified date by looking only at the date
of the originally requested file, ignoring the modification date of
any included files. </li>
<li>Use the directives provided by <a
href="../mod/mod_expires.html">mod_expires</a> to set an
explicit expiration time on your files, thereby letting
browsers and proxies know that it is acceptable to cache
them.</li>
</ol>
<hr />
<li>Use the directives provided by <a
href="../mod/mod_expires.html">mod_expires</a> to set an explicit
expiration time on your files, thereby letting browsers and proxies
know that it is acceptable to cache them. </li>
</ol>
<hr>
<h2><a name="basicssidirectives">Basic SSI directives</a></h2>
<p>SSI directives have the following syntax:</p>
<h2><a id="basicssidirectives" name="basicssidirectives">Basic
SSI directives</a></h2>
<p>SSI directives have the following syntax:</p>
<pre>
&lt;!--#element attribute=value attribute=value ... --&gt;
</pre>
<p>It is formatted like an HTML comment, so if you don't have SSI
correctly enabled, the browser will ignore it, but it will still be
visible in the HTML source. If you have SSI correctly configured, the
directive will be replaced with its results.</p>
<p>It is formatted like an HTML comment, so if you don't have
SSI correctly enabled, the browser will ignore it, but it will
still be visible in the HTML source. If you have SSI correctly
configured, the directive will be replaced with its
results.</p>
<p>The element can be one of a number of things, and we'll talk some
more about most of these in the next installment of this series. For
now, here are some examples of what you can do with SSI</p>
<h3><a name="today'sdate">Today's date</a></h3>
<p>The element can be one of a number of things, and we'll talk
some more about most of these in the next installment of this
series. For now, here are some examples of what you can do with
SSI</p>
<h3><a id="today'sdate" name="today'sdate">Today's
date</a></h3>
<pre>
&lt;!--#echo var="DATE_LOCAL" --&gt;
</pre>
<p>The <code>echo</code> element just spits out the value of a
variable. There are a number of standard variables, which include the
whole set of environment variables that are available to CGI programs.
Also, you can define your own variables with the <code>set</code>
element.</p>
<p>If you don't like the format in which the date gets printed, you can
use the <code>config</code> element, with a <code>timefmt</code>
attribute, to modify that formatting.</p>
<p>The <code>echo</code> element just spits out the value of a
variable. There are a number of standard variables, which
include the whole set of environment variables that are
available to CGI programs. Also, you can define your own
variables with the <code>set</code> element.</p>
<p>If you don't like the format in which the date gets printed,
you can use the <code>config</code> element, with a
<code>timefmt</code> attribute, to modify that formatting.</p>
<pre>
&lt;!--#config timefmt="%A %B %d, %Y" --&gt;
Today is &lt;!--#echo var="DATE_LOCAL" --&gt;
</pre>
<h3><a name="modificationdateofthefile">Modification date of the
file</a></h3>
<h3><a id="modificationdateofthefile"
name="modificationdateofthefile">Modification date of the
file</a></h3>
<pre>
This document last modified &lt;!--#flastmod file="index.html" --&gt;
</pre>
<p>This element is also subject to <code>timefmt</code> format
configurations.</p>
<p>This element is also subject to <code>timefmt</code> format
configurations.</p>
<h3><a name="includingtheresultsofacgiprogram">Including the
results of a CGI program</a></h3>
<p>This is one of the more common uses of SSI - to output the results
of a CGI program, such as everybody's favorite, a ``hit counter.''</p>
<h3><a id="includingtheresultsofacgiprogram"
name="includingtheresultsofacgiprogram">Including the results
of a CGI program</a></h3>
<p>This is one of the more common uses of SSI - to output the
results of a CGI program, such as everybody's favorite, a ``hit
counter.''</p>
<pre>
&lt;!--#include virtual="/cgi-bin/counter.pl" --&gt;
</pre>
<hr />
<hr>
<h2><a name="additionalexamples">Additional examples</a></h2>
<h2><a id="additionalexamples"
name="additionalexamples">Additional examples</a></h2>
<p>Following are some specific examples of things you can do in your
HTML documents with SSI.</p>
<p>Following are some specific examples of things you can do in
your HTML documents with SSI.</p>
<hr />
<hr>
<h2><a name="whenwasthisdocumentmodified">When was this document
modified?</a></h2>
<p>Earlier, we mentioned that you could use SSI to inform the user when
the document was most recently modified. However, the actual method for
doing that was left somewhat in question. The following code, placed in
your HTML document, will put such a time stamp on your page. Of course,
you will have to have SSI correctly enabled, as discussed above.</p>
<h2><a id="whenwasthisdocumentmodified"
name="whenwasthisdocumentmodified">When was this document
modified?</a></h2>
<p>Earlier, we mentioned that you could use SSI to inform the
user when the document was most recently modified. However, the
actual method for doing that was left somewhat in question. The
following code, placed in your HTML document, will put such a
time stamp on your page. Of course, you will have to have SSI
correctly enabled, as discussed above.</p>
<pre>
&lt;!--#config timefmt="%A %B %d, %Y" --&gt;
This file last modified &lt;!--#flastmod file="ssi.shtml" --&gt;
</pre>
<p>Of course, you will need to replace the <code>ssi.shtml</code> with
the actual name of the file that you're referring to. This can be
inconvenient if you're just looking for a generic piece of code that
you can paste into any file, so you probably want to use the
<code>LAST_MODIFIED</code> variable instead:</p>
<p>Of course, you will need to replace the
<code>ssi.shtml</code> with the actual name of the file that
you're referring to. This can be inconvenient if you're just
looking for a generic piece of code that you can paste into any
file, so you probably want to use the
<code>LAST_MODIFIED</code> variable instead:</p>
<pre>
&lt;!--#config timefmt="%D" --&gt;
This file last modified &lt;!--#echo var="LAST_MODIFIED" --&gt;
</pre>
<p>For more details on the <code>timefmt</code> format, go to your
favorite search site and look for <code>ctime</code>. The syntax is the
same.</p>
<p>For more details on the <code>timefmt</code> format, go to
your favorite search site and look for <code>ctime</code>. The
syntax is the same.</p>
<hr />
<hr>
<h2><a name="includingastandardfooter">Including a standard
footer</a></h2>
<h2><a id="includingastandardfooter"
name="includingastandardfooter">Including a standard
footer</a></h2>
<p>If you are managing any site that is more than a few pages, you may
find that making changes to all those pages can be a real pain,
particularly if you are trying to maintain some kind of standard look
across all those pages.</p>
<p>Using an include file for a header and/or a footer can reduce the
burden of these updates. You just have to make one footer file, and
then include it into each page with the <code>include</code> SSI
command. The <code>include</code> element can determine what file to
include with either the <code>file</code> attribute, or the
<code>virtual</code> attribute. The <code>file</code> attribute is a
file path, <em>relative to the current directory</em>. That means that
it cannot be an absolute file path (starting with /), nor can it
contain ../ as part of that path. The <code>virtual</code> attribute is
probably more useful, and should specify a URL relative to the document
being served. It can start with a /, but must be on the same server as
the file being served.</p>
<p>If you are managing any site that is more than a few pages,
you may find that making changes to all those pages can be a
real pain, particularly if you are trying to maintain some kind
of standard look across all those pages.</p>
<p>Using an include file for a header and/or a footer can
reduce the burden of these updates. You just have to make one
footer file, and then include it into each page with the
<code>include</code> SSI command. The <code>include</code>
element can determine what file to include with either the
<code>file</code> attribute, or the <code>virtual</code>
attribute. The <code>file</code> attribute is a file path,
<em>relative to the current directory</em>. That means that it
cannot be an absolute file path (starting with /), nor can it
contain ../ as part of that path. The <code>virtual</code>
attribute is probably more useful, and should specify a URL
relative to the document being served. It can start with a /,
but must be on the same server as the file being served.</p>
<pre>
&lt;!--#include virtual="/footer.html" --&gt;
</pre>
<p>I'll frequently combine the last two things, putting a
<code>LAST_MODIFIED</code> directive inside a footer file to be
included. SSI directives can be contained in the included file, and
includes can be nested - that is, the included file can include another
file, and so on.</p>
<p>I'll frequently combine the last two things, putting a
<code>LAST_MODIFIED</code> directive inside a footer file to be
included. SSI directives can be contained in the included file,
and includes can be nested - that is, the included file can
include another file, and so on.</p>
<hr />
<hr>
<h2><a name="whatelsecaniconfig">What else can I config?</a></h2>
<h2><a id="whatelsecaniconfig" name="whatelsecaniconfig">What
else can I config?</a></h2>
<p>In addition to being able to <code>config</code> the time format,
you can also <code>config</code> two other things.</p>
<p>Usually, when something goes wrong with your SSI directive, you get
the message</p>
<p>In addition to being able to <code>config</code> the time
format, you can also <code>config</code> two other things.</p>
<p>Usually, when something goes wrong with your SSI directive,
you get the message</p>
<pre>
[an error occurred while processing this directive]
</pre>
<p>If you want to change that message to something else, you can do so
with the <code>errmsg</code> attribute to the <code>config</code>
element:</p>
<p>If you want to change that message to something else, you
can do so with the <code>errmsg</code> attribute to the
<code>config</code> element:</p>
<pre>
&lt;!--#config errmsg="[It appears that you don't know how to use SSI]" --&gt;
</pre>
<p>Hopefully, end users will never see this message, because you will
have resolved all the problems with your SSI directives before your
site goes live. (Right?)</p>
<p>Hopefully, end users will never see this message, because
you will have resolved all the problems with your SSI
directives before your site goes live. (Right?)</p>
<p>And you can <code>config</code> the format in which file sizes are
returned with the <code>sizefmt</code> attribute. You can specify
<code>bytes</code> for a full count in bytes, or <code>abbrev</code>
for an abbreviated number in Kb or Mb, as appropriate.</p>
<p>And you can <code>config</code> the format in which file
sizes are returned with the <code>sizefmt</code> attribute. You
can specify <code>bytes</code> for a full count in bytes, or
<code>abbrev</code> for an abbreviated number in Kb or Mb, as
appropriate.</p>
<hr />
<hr>
<h2><a name="executingcommands">Executing commands</a></h2>
<p>I expect that I'll have an article some time in the coming months
about using SSI with small CGI programs. For now, here's something else
that you can do with the <code>exec</code> element. You can actually
have SSI execute a command using the shell (<code>/bin/sh</code>, to be
precise - or the DOS shell, if you're on Win32). The following, for
example, will give you a directory listing.</p>
<h2><a id="executingcommands"
name="executingcommands">Executing commands</a></h2>
<p>I expect that I'll have an article some time in the coming
months about using SSI with small CGI programs. For now, here's
something else that you can do with the <code>exec</code>
element. You can actually have SSI execute a command using the
shell (<code>/bin/sh</code>, to be precise - or the DOS shell,
if you're on Win32). The following, for example, will give you
a directory listing.</p>
<pre>
&lt;pre&gt;
&lt;!--#exec cmd="ls" --&gt;
&lt;/pre&gt;
</pre>
<p>or, on Windows</p>
<p>or, on Windows</p>
<pre>
&lt;pre&gt;
&lt;!--#exec cmd="dir" --&gt;
&lt;/pre&gt;
</pre>
<p>You might notice some strange formatting with this directive on
Windows, because the output from <code>dir</code> contains the string
``&lt;<code>dir</code>&gt;'' in it, which confuses browsers.</p>
<p>You might notice some strange formatting with this directive
on Windows, because the output from <code>dir</code> contains
the string ``&lt;<code>dir</code>&gt;'' in it, which confuses
browsers.</p>
<p>Note that this feature is exceedingly dangerous, as it will execute
whatever code happens to be embedded in the <code>exec</code> tag. If
you have any situation where users can edit content on your web pages,
such as with a ``guestbook'', for example, make sure that you have this
feature disabled. You can allow SSI, but not the <code>exec</code>
feature, with the <code>IncludesNOEXEC</code> argument to the
<code>Options</code> directive.</p>
<p>Note that this feature is exceedingly dangerous, as it will
execute whatever code happens to be embedded in the
<code>exec</code> tag. If you have any situation where users
can edit content on your web pages, such as with a
``guestbook'', for example, make sure that you have this
feature disabled. You can allow SSI, but not the
<code>exec</code> feature, with the <code>IncludesNOEXEC</code>
argument to the <code>Options</code> directive.</p>
<hr />
<hr>
<h2><a name="advancedssitechniques">Advanced SSI techniques</a></h2>
<h2><a id="advancedssitechniques"
name="advancedssitechniques">Advanced SSI techniques</a></h2>
<p>In addition to spitting out content, Apache SSI gives you the option
of setting variables, and using those variables in comparisons and
conditionals.</p>
<p>In addition to spitting out content, Apache SSI gives you
the option of setting variables, and using those variables in
comparisons and conditionals.</p>
<h3><a name="caveat">Caveat</a></h3>
<h3><a id="caveat" name="caveat">Caveat</a></h3>
<p>Most of the features discussed in this article are only available to
you if you are running Apache 1.2 or later. Of course, if you are not
running Apache 1.2 or later, you need to upgrade immediately, if not
sooner. Go on. Do it now. We'll wait.</p>
<p>Most of the features discussed in this article are only
available to you if you are running Apache 1.2 or later. Of
course, if you are not running Apache 1.2 or later, you need to
upgrade immediately, if not sooner. Go on. Do it now. We'll
wait.</p>
<hr />
<hr>
<h2><a name="settingvariables">Setting variables</a></h2>
<p>Using the <code>set</code> directive, you can set variables for
later use. We'll need this later in the discussion, so we'll talk about
it here. The syntax of this is as follows:</p>
<h2><a id="settingvariables" name="settingvariables">Setting
variables</a></h2>
<p>Using the <code>set</code> directive, you can set variables
for later use. We'll need this later in the discussion, so
we'll talk about it here. The syntax of this is as follows:</p>
<pre>
&lt;!--#set var="name" value="Rich" --&gt;
</pre>
<p>In addition to merely setting values literally like that, you can
use any other variable, including, for example, environment variables,
or some of the variables we discussed in the last article (like
<code>LAST_MODIFIED</code>, for example) to give values to your
variables. You will specify that something is a variable, rather than a
literal string, by using the dollar sign ($) before the name of the
variable.</p>
<p>In addition to merely setting values literally like that,
you can use any other variable, including, for example,
environment variables, or some of the variables we discussed in
the last article (like <code>LAST_MODIFIED</code>, for example)
to give values to your variables. You will specify that
something is a variable, rather than a literal string, by using
the dollar sign ($) before the name of the variable.</p>
<pre>
&lt;!--#set var="modified" value="$LAST_MODIFIED" --&gt;
</pre>
<p>To put a literal dollar sign into the value of your variable, you
need to escape the dollar sign with a backslash.</p>
<p>To put a literal dollar sign into the value of your
variable, you need to escape the dollar sign with a
backslash.</p>
<pre>
&lt;!--#set var="cost" value="\$100" --&gt;
</pre>
<p>Finally, if you want to put a variable in the midst of a longer
string, and there's a chance that the name of the variable will run up
against some other characters, and thus be confused with those
characters, you can place the name of the variable in braces, to remove
this confusion. (It's hard to come up with a really good example of
this, but hopefully you'll get the point.)</p>
<p>Finally, if you want to put a variable in the midst of a
longer string, and there's a chance that the name of the
variable will run up against some other characters, and thus be
confused with those characters, you can place the name of the
variable in braces, to remove this confusion. (It's hard to
come up with a really good example of this, but hopefully
you'll get the point.)</p>
<pre>
&lt;!--#set var="date" value="${DATE_LOCAL}_${DATE_GMT}" --&gt;
</pre>
<hr />
<hr>
<h2><a name="conditionalexpressions">Conditional expressions</a></h2>
<h2><a id="conditionalexpressions"
name="conditionalexpressions">Conditional expressions</a></h2>
<p>Now that we have variables, and are able to set and compare their
values, we can use them to express conditionals. This lets SSI be a
tiny programming language of sorts. <code>mod_include</code> provides
an <code>if</code>, <code>elif</code>, <code>else</code>,
<code>endif</code> structure for building conditional statements. This
allows you to effectively generate multiple logical pages out of one
actual page.</p>
<p>The structure of this conditional construct is:</p>
<p>Now that we have variables, and are able to set and compare
their values, we can use them to express conditionals. This
lets SSI be a tiny programming language of sorts.
<code>mod_include</code> provides an <code>if</code>,
<code>elif</code>, <code>else</code>, <code>endif</code>
structure for building conditional statements. This allows you
to effectively generate multiple logical pages out of one
actual page.</p>
<p>The structure of this conditional construct is:</p>
<pre>
&lt;!--#if expr="test_condition" --&gt;
&lt;!--#elif expr="test_condition" --&gt;
@ -466,25 +492,27 @@ actual page.</p>
&lt;!--#endif --&gt;
</pre>
<p>A <em>test_condition</em> can be any sort of logical comparison -
either comparing values to one another, or testing the ``truth'' of a
particular value. (A given string is true if it is nonempty.) For a
full list of the comparison operators available to you, see the
<code>mod_include</code> documentation. Here are some examples of how
one might use this construct.</p>
<p>In your configuration file, you could put the following line:</p>
<p>A <em>test_condition</em> can be any sort of logical
comparison - either comparing values to one another, or testing
the ``truth'' of a particular value. (A given string is true if
it is nonempty.) For a full list of the comparison operators
available to you, see the <code>mod_include</code>
documentation. Here are some examples of how one might use this
construct.</p>
<p>In your configuration file, you could put the following
line:</p>
<pre>
BrowserMatchNoCase macintosh Mac
BrowserMatchNoCase MSIE InternetExplorer
</pre>
<p>This will set environment variables ``Mac'' and ``InternetExplorer''
to true, if the client is running Internet Explorer on a Macintosh.</p>
<p>Then, in your SSI-enabled document, you might do the following:</p>
<p>This will set environment variables ``Mac'' and
``InternetExplorer'' to true, if the client is running Internet
Explorer on a Macintosh.</p>
<p>Then, in your SSI-enabled document, you might do the
following:</p>
<pre>
&lt;!--#if expr="${Mac} &amp;&amp; ${InternetExplorer}" --&gt;
Apologetic text goes here
@ -493,27 +521,26 @@ to true, if the client is running Internet Explorer on a Macintosh.</p>
&lt;!--#endif --&gt;
</pre>
<p>Not that I have anything against IE on Macs - I just struggled for a
few hours last week trying to get some JavaScript working on IE on a
Mac, when it was working everywhere else. The above was the interim
workaround.</p>
<p>Not that I have anything against IE on Macs - I just
struggled for a few hours last week trying to get some
JavaScript working on IE on a Mac, when it was working
everywhere else. The above was the interim workaround.</p>
<p>Any other variable (either ones that you define, or normal
environment variables) can be used in conditional statements. With
Apache's ability to set environment variables with the
<code>SetEnvIf</code> directives, and other related directives, this
functionality can let you do some pretty involved dynamic stuff without
ever resorting to CGI.</p>
<p>Any other variable (either ones that you define, or normal
environment variables) can be used in conditional statements.
With Apache's ability to set environment variables with the
<code>SetEnvIf</code> directives, and other related directives,
this functionality can let you do some pretty involved dynamic
stuff without ever resorting to CGI.</p>
<hr />
<hr>
<h2><a name="conclusion">Conclusion</a></h2>
<h2><a id="conclusion" name="conclusion">Conclusion</a></h2>
<p>SSI is certainly not a replacement for CGI, or other technologies
used for generating dynamic web pages. But it is a great way to add
small amounts of dynamic content to pages, without doing a lot of extra
work.</p>
<!--#include virtual="footer.html" -->
</body>
<p>SSI is certainly not a replacement for CGI, or other
technologies used for generating dynamic web pages. But it is a
great way to add small amounts of dynamic content to pages,
without doing a lot of extra work.</p>
<!--#include virtual="footer.html" -->
</body>
</html>