Configuration 4 GNU (CFG)
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Backend | | |
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The backend consists primarily of parsers which are responsible for
the translation between XML and the native config files. The
parsers may be written in any language, however it is strongly
encouraged to use Perl because nearly all *nix systems have Perl,
and a useful Perl module exists which handles many common tasks in a
uniform way. To add support for a new configuration entity, an
existing parser can often be extended with minimal effort, leaving
only the task of creating type definitions for your parser's XML.
![[Note]](/docbook-images/note.png) | Note |
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When referring to parsers, often the
CFGXML::Parser:: beginning of
the parser's full module name is omitted for readability.
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Extending the Parser Backend
The existing CFGXML::Parser,
config4gnu::CfgObject, and related Perl
modules provide many functions and options which handle most of
the work for you. For reference, if your parser is more than 200
lines at most then you're probably either not using the libraries
to the extent you could be, or you should put some of your code
into functions and submit them for inclusion in the standard
CFGXML::Parser module.
To create a new parser, one of two approaches can be used.
Either subclass an existing Perl parser using Perl's inheritance
system or write a completely new parser from scratch. Generally,
you should use the first approach if a parser for the
configuration file format that you're adding
already exists, for example the
App::Samba::Default parser was created by
extending the Common::Ini parser which handles the
INI-style formatted configuration files.
If no parser for the format you need exists create
two parsers, the generic parser for the
format (i.e., INI), and the parser for the particular application
which you are adding support for. Generally the generic parser
goes in CFGXML::Parser::Common::YourFormat
and the specific parser goes in either
CFGXML::Parser::App or
CFGXML::Parser::Distro. Doing this takes
little extra work but allows others to extend your base parser for
other applications.
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