Apache Module mod_macro

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

Summary

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.

Topics

Features
Examples

Comments

Features

Definition of a macro:

macro definition within a <Macro> section, following the httpd configuration style.
user defined names for the macro and its parameters.
macro names are case-insensitive, like httpd directives.
macro parameter names are case sensitive.
macro parameters must have distinct names.
error on empty parameter names.
redefining a macro generates a warning.
macro definitions can be nested... (but what for?)
warn about unused macro parameters.
warn about macro parameter names which prefix one another.
warn if a parameter is not prefixed by any of '$%@' (good practice).
the available prefixes help deal with interactions with other directives such as Define.
tip: it may be useful to define a macro parameter with surrounding braces, say ${foo} so that the name can appear with surrounding characters such as bla${foo}bla.
warn about empty macro contents.
warns if sections are not properly nested within a macro. (if it is detected so).
the lexical scope of macro parameters is restricted to the macro text, it is not forwarded to includes for instance.
arbitrary contents in macros.
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.

Use of a macro:

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

Removal of a macro definition:

the macro must be already defined.

<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

Examples

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

    <Directory $dir>
      # do something here...
    </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

<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 than 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