apache/docs/manual/mod/mod_macro.xml

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<modulesynopsis metafile="mod_macro.xml.meta">

<name>mod_macro</name>
<description>Provides macros within apache httpd runtime configuration files</description>
<status>Base</status>
<sourcefile>mod_macro.c</sourcefile>
<identifier>macro_module</identifier>

<summary>

    <p>This modules provides macros within apache httpd runtime configuration files.
    These macros may have parameters. They are expanded when used (parameters are
    substituted by their values given as an argument), and the result is
    processed normally.</p>
</summary>

<section id="features"><title>Features</title>

<p>Definition of a macro:</p>

    <ul>
    <li> macro definition within a <directive type="section">Macro</directive> section, following
         the httpd configuration style.</li>
    <li> user defined names for the macro and its parameters.</li>
    <li> macro names are case-insensitive, like httpd directives.</li>
    <li> macro parameter names are case sensitive.</li>
    <li> macro parameters must have distinct names.</li>
    <li> error on empty parameter names.</li>
    <li> redefining a macro generates a warning.</li>
    <li> macro definitions can be nested... (but what for?)</li>
    <li> warn about unused macro parameters.</li>
    <li> warn about macro parameter names which prefix one another.</li>
    <li> warn if a parameter is not prefixed by any of '<code>$%@</code>'
         (good practice).</li>
    <li> the available prefixes help deal with interactions with other
         directives such as <directive module="core">Define</directive>.</li>
    <li> tip: it may be useful to define a macro parameter with surrounding
         braces, say <code>${foo}</code> so that the name can appear with
	 surrounding characters such as <code>bla${foo}bla</code>.</li>
    <li> warn about empty macro contents.</li>
    <li> warns if sections are not properly nested within a macro.
         (if it is detected so).</li>
    <li> the lexical scope of macro parameters is restricted to the macro text,
         it is not forwarded to includes for instance.</li>
    <li> arbitrary contents in macros.
         <p>It means you can put perl sections or whatever you like in a macro.
	 No assumption is made about the lexical structure (quotes, spaces or
         whatever) within the macro contents but to expect a set of
         backslash-continued independent lines.</p></li>
    </ul>

<p>Use of a macro:</p>

    <ul>
    <li> number of arguments must match the definition.</li>
    <li> all occurences of macro parameters are substituted by their values.</li>
    <li> in case of conflicts, the longest parameter name is chosen.</li>
    <li> macro expansion recursion is detected and stopped (error).</li>
    <li> warn about empty arguments when used.</li>
    <li> on errors, try to describe precisely where the error occured.</li>
    <li> <code>$</code> and <code>%</code>-prefixed parameters are not
          escaped.</li>
    <li> <code>@</code>-prefixed parameters are escaped in quotes.</li>
    </ul>

<p>Removal of a macro definition:</p>

   <ul>
   <li> the macro must be already defined.</li>
   </ul>

<highlight language="config">
&lt;Macro DirGroup $dir $group&gt;
  &lt;Directory $dir&gt;
    require group $group
  &lt;/Directory&gt;
&lt;/Macro&gt;

Use DirGroup /www/apache/private private
Use DirGroup /www/apache/server  admin

UndefMacro DirGroup
</highlight>

</section>

<section id="examples"><title>Examples</title>

<p>A common usage of <module>mod_macro</module> is for the creation of
dynamically-generated virtual hosts.</p>

<highlight language="config">
## Define a VHost Macro for repetitive configurations

&lt;Macro VHost $host $port $dir&gt;
  Listen $port
  &lt;VirtualHost *:$port&gt;

    ServerName $host
    DocumentRoot $dir

    &lt;Directory $dir&gt;
      # do something here...
    &lt;/Directory&gt;

    # limit access to intranet subdir.
    &lt;Directory $dir/intranet&gt;
      Require ip 10.0.0.0/8
    &lt;/Directory&gt;
  &lt;/VirtualHost&gt;
&lt;/Macro&gt;

## Use of VHost with different arguments.

Use VHost www.apache.org 80 /vhosts/apache/htdocs
Use VHost example.org 8080 /vhosts/example/htdocs
Use VHost www.example.fr 1234 /vhosts/example.fr/htdocs
</highlight>

</section>

<!-- Macro -->
<directivesynopsis type="section">
<name>Macro</name>
<description>Define a configuration file macro</description>
<syntax>
&lt;Macro <var>name</var> [<var>par1</var> .. <var>parN</var>]&gt;
... &lt;/Macro&gt;</syntax>
<contextlist>
<context>server config</context>
<context>virtual host</context>
<context>directory</context>
</contextlist>

<usage>
    <p>The <directive>Macro</directive> directive controls the definition of
    a macro within the server runtime configuration files.
    The first argument is the name of the macro.
    Other arguments are parameters to the macro. It is good practice to prefix
    parameter names with any of '<code>$%@</code>', and not macro names
    with such characters.
    </p>

    <highlight language="config">
&lt;Macro LocalAccessPolicy&gt;
    Require ip 10.2.16.0/24
&lt;/Macro&gt;

&lt;Macro RestrictedAccessPolicy $ipnumbers&gt;
    Require ip $ipnumbers
&lt;/Macro&gt;
    </highlight>
</usage>
</directivesynopsis>

<!-- Use -->
<directivesynopsis>
<name>Use</name>
<description>Use a macro</description>
<syntax>Use <var>name</var> [<var>value1</var> ... <var>valueN</var>]
</syntax>
<contextlist>
<context>server config</context>
<context>virtual host</context>
<context>directory</context>
</contextlist>

<usage>
    <p>The <directive>Use</directive> directive controls the use of a macro.
    The specified macro is expanded. It must be given the same number of
    arguments than in the  macro definition. The provided values are
    associated to their corresponding initial parameters and are substituted
    before processing.</p>

    <highlight language="config">
Use LocalAccessPolicy
...
Use RestrictedAccessPolicy "192.54.172.0/24 192.54.148.0/24"
    </highlight>

    <p>is equivalent, with the macros defined above, to:</p>

    <highlight language="config">
Require ip 10.2.16.0/24
...
Require ip 192.54.172.0/24 192.54.148.0/24
    </highlight>
</usage>

</directivesynopsis>

<!-- UndefMacro -->
<directivesynopsis>
<name>UndefMacro</name>
<description>Undefine a macro</description>

<syntax>UndefMacro <var>name</var></syntax>
<contextlist>
<context>server config</context>
<context>virtual host</context>
<context>directory</context>
</contextlist>

<usage>
    <p>The <directive>UndefMacro</directive> directive undefines a macro
    which has been defined before hand.</p>

    <highlight language="config">
UndefMacro LocalAccessPolicy
UndefMacro RestrictedAccessPolicy
    </highlight>
</usage>
</directivesynopsis>
</modulesynopsis>