Apache HTTP Server Version 2.4

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# Apache Module mod_macro

Description: | Provides macros within apache httpd runtime configuration files
Status: | Base
Module Identifier: | macro_module
Source File: | mod_macro.c

### Summary

Provides macros within Apache httpd runtime configuration files, to ease the process of creating numerous similar configuration blocks. When the server starts up, the macros are expanded using the provided parameters, and the result is processed as along with the rest of the configuration file.

### Topics

- Usage
- Tips
- Examples

### Directives

### Bugfix checklist

- httpd changelog
- Known issues
- Report a bug

## Usage

Macros are defined using `<Macro>` blocks, which contain the portion of your configuration that needs to be repeated, complete with variables for those parts that will need to be substituted.

For example, you might use a macro to define a `<VirtualHost>` block, in order to define multiple similar virtual hosts:

    <Macro VHost $name $domain>
    <VirtualHost *:80>
        ServerName $domain
        ServerAlias www.$domain

        DocumentRoot "/var/www/vhosts/$name"
        ErrorLog "/var/log/httpd/$name.error_log"
        CustomLog "/var/log/httpd/$name.access_log" combined
    </VirtualHost>
    </Macro>

Macro names are case-insensitive, like httpd configuration directives. However, variable names are case sensitive.

You would then invoke this macro several times to create virtual hosts:

    Use VHost example example.com
    Use VHost myhost hostname.org
    Use VHost apache apache.org

    UndefMacro VHost

At server startup time, each of these `Use` invocations would be expanded into a full virtualhost, as described by the `<Macro>` definition.

The `UndefMacro` directive is used so that later macros using the same variable names don't result in conflicting definitions.

A more elaborate version of this example may be seen below in the Examples section.

## Tips

Parameter names should begin with a sigil such as `$`, `%`, or `@`, so that they are clearly identifiable, and also in order to help deal with interactions with other directives, such as the core `Define` directive. Failure to do so will result in a warning. Nevertheless, you are encouraged to have a good knowledge of your entire server configuration in order to avoid reusing the same variables in different scopes, which can cause confusion.

Parameters prefixed with either `$` or `%` are not escaped. Parameters prefixes with `@` are escaped in quotes.

Avoid using a parameter which contains another parameter as a prefix, (For example, `$win` and `$winter`) as this may cause confusion at expression evaluation time. In the event of such confusion, the longest possible parameter name is used.

If you want to use a value within another string, it is useful to surround the parameter in braces, to avoid confusion:

    <Macro DocRoot ${docroot}>
        DocumentRoot "/var/www/${docroot}/htdocs"
    </Macro>

## Examples

### Virtual Host Definition

A common usage of `mod_macro` is for the creation of dynamically-generated virtual hosts.

    ## Define a VHost Macro for repetitive configurations

    <Macro VHost $host $port $dir>
      Listen $port
      <VirtualHost *:$port>

        ServerName $host
        DocumentRoot "$dir"

        # Public document root
        <Directory "$dir">
            Require all granted
        </Directory>

        # limit access to intranet subdir.
        <Directory "$dir/intranet">
          Require ip 10.0.0.0/8
        </Directory>
      </VirtualHost>
    </Macro>

    ## 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

### Removal of a macro definition

It's recommended that you undefine a macro once you've used it. This avoids confusion in a complex configuration file where there may be conflicts in variable names.

    <Macro DirGroup $dir $group>
      <Directory "$dir">
        Require group $group
      </Directory>
    </Macro>

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

    UndefMacro DirGroup

## <Macro> Directive

Description: | Define a configuration file macro
Syntax: | `<Macro name [par1 .. parN]> ... </Macro>`
Context: | server config, virtual host, directory
Status: | Base
Module: | mod_macro

The `<Macro>` 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 '`$%@`', and not macro names with such characters.

    <Macro LocalAccessPolicy>
        Require ip 10.2.16.0/24
    </Macro>

    <Macro RestrictedAccessPolicy $ipnumbers>
        Require ip $ipnumbers
    </Macro>

## UndefMacro Directive

Description: | Undefine a macro
Syntax: | `UndefMacro name`
Context: | server config, virtual host, directory
Status: | Base
Module: | mod_macro

The `UndefMacro` directive undefines a macro which has been defined before hand.

    UndefMacro LocalAccessPolicy
    UndefMacro RestrictedAccessPolicy

## Use Directive

Description: | Use a macro
Syntax: | `Use name [value1 ... valueN]`
Context: | server config, virtual host, directory
Status: | Base
Module: | mod_macro

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

    Use LocalAccessPolicy
    ...
    Use RestrictedAccessPolicy "192.54.172.0/24 192.54.148.0/24"

is equivalent, with the macros defined above, to:

    Require ip 10.2.16.0/24
    ...
    Require ip 192.54.172.0/24 192.54.148.0/24