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Config::Grammar(3)    User Contributed Perl Documentation   Config::Grammar(3)

NAME
       Config::Grammar - A grammar-based, user-friendly config parser

SYNOPSIS
	use Config::Grammar;

	my $parser = Config::Grammar->new(\%grammar);
	my $cfg = $parser->parse('app.cfg') or die "ERROR: $parser->{err}\n";
	my $pod = $parser->makepod();
	my $ex = $parser->maketmpl('TOP','SubNode');
	my $minex = $parser->maketmplmin('TOP','SubNode');

DESCRIPTION
       Config::Grammar is a module to parse configuration files. The
       configuration may consist of multiple-level sections with assignments
       and tabular data. The parsed data will be returned as a hash containing
       the whole configuration. Config::Grammar uses a grammar that is
       supplied upon creation of a Config::Grammar object to parse the
       configuration file and return helpful error messages in case of syntax
       errors. Using the makepod method you can generate documentation of the
       configuration file format.

       The maketmpl method can generate a template configuration file.	If
       your grammar contains regexp matches, the template will not be all that
       helpful as Config::Grammar is not smart enough to give you sensible
       template data based in regular expressions. The related function
       maketmplmin generates a minimal configuration template without
       examples, regexps or comments and thus allows an experienced user to
       fill in the configuration data more efficiently.

   Grammar Definition
       The grammar is a multiple-level hash of hashes, which follows the
       structure of the configuration. Each section or variable is represented
       by a hash with the same structure.  Each hash contains special keys
       starting with an underscore such as '_sections', '_vars', '_sub' or
       '_re' to denote meta data with information about that section or
       variable. Other keys are used to structure the hash according to the
       same nesting structure of the configuration itself. The starting hash
       given as parameter to 'new' contains the "root section".

       Special Section Keys

       _sections   Array containing the list of sub-sections of this section.
		   Each sub-section must then be represented by a sub-hash in
		   this hash with the same name of the sub-section.

		   The sub-section can also be a regular expression denoted by
		   the syntax '/re/', where re is the regular-expression. In
		   case a regular expression is used, a sub-hash named with
		   the same '/re/' must be included in this hash.

       _vars	   Array containing the list of variables (assignments) in
		   this section.  Analogous to sections, regular expressions
		   can be used.

       _mandatory  Array containing the list of mandatory sections and
		   variables.

       _inherited  Array containing the list of the variables that should be
		   assigned the same value as in the parent section if nothing
		   is specified here.

       _table	   Hash containing the table grammar (see Special Table Keys).
		   If not specified, no table is allowed in this section. The
		   grammar of the columns if specified by sub-hashes named
		   with the column number.

       _text	   Section contains free-form text. Only sections and
		   @includes statements will be interpreted, the rest will be
		   added in the returned hash under '_text' as string.

		   _text is a hash reference which can contain a _re and a
		   _re_error key which will be used to scrutanize the text ...
		   if the hash is empty, all text will be accepted.

       _order	   If defined, a '_order' element will be put in every hash
		   containing the sections with a number that determines the
		   order in which the sections were defined.

       _doc	   Describes what this section is about

       _sub	   A function pointer. It is called for every instance of this
		   section, with the real name of the section passed as its
		   first argument. This is probably only useful for the regexp
		   sections. If the function returns a defined value it is
		   assumed that the test was not successful and an error is
		   generated with the returned string as content.

       Special Variable Keys

       _re	   Regular expression upon which the value will be checked.

       _re_error   String containing the returned error in case the regular
		   expression doesn't match (if not specified, a generic
		   'syntax error' message will be returned).

       _sub	   A function pointer. It called for every value, with the
		   value passed as its first argument. If the function returns
		   a defined value it is assumed that the test was not
		   successful and an error is generated with the returned
		   string as content.

		   If the '_varlist' key (see above) is defined in this
		   section, the '_sub' function will also receive an array
		   reference as the second argument. The array contains a list
		   of those variables already defined in the same section.
		   This can be used to enforce the order of the variables.

       _default	   A default value that will be assigned to the variable if
		   none is specified or inherited.

       _doc	   Description of the variable.

       _example	   A one line example for the content of this variable.

       Special Table Keys

       _columns	   Number of columns. If not specified, it will not be
		   enforced.

       _key	   If defined, the specified column number will be used as key
		   in a hash in the returned hash. If not defined, the
		   returned hash will contain a '_table' element with the
		   contents of the table as array. The rows of the tables are
		   stored as arrays.

       _sub	   they work analog to the description in the previous
		   section.

       _doc	   describes the content of the column.

       _example	   example for the content of this column

       Special Text Keys

       _re	   Regular expression upon which the text will be checked
		   (everything as a single line).

       _re_error   String containing the returned error in case the regular
		   expression doesn't match (if not specified, a generic
		   'syntax error' message will be returned).

       _sub	   they work analog to the description in the previous
		   section.

       _doc	   Ditto.

       _example	   Potential multi line example for the content of this text
		   section

   Configuration Syntax
       General Syntax

       '#' denotes a comment up to the end-of-line, empty lines are allowed
       and space at the beginning and end of lines is trimmed.

       '\' at the end of the line marks a continued line on the next line. A
       single space will be inserted between the concatenated lines.

       '@include filename' is used to include another file. Include works
       relative to the directory where the parent file is in.

       '@define a some value' will replace all occurences of 'a' in the
       following text with 'some value'.

       Fields in tables that contain white space can be enclosed in either "'"
       or """.	Whitespace can also be escaped with "\". Quotes inside quotes
       are allowed but must be escaped with a backslash as well.

       Sections

       Config::Grammar supports hierarchical configurations through sections,
       whose syntax is as follows:

       Level 1	      *** section name ***

       Level 2	      + section name

       Level 3	      ++ section name

       Level n, n>1   +..+ section name (number of '+' determines level)

       Assignments

       Assignements take the form: 'variable = value', where value can be any
       string (can contain whitespaces and special characters). The spaces
       before and after the equal sign are optional.

       Tabular Data

       The data is interpreted as one or more columns separated by spaces.

   Example
       Code

	use Data::Dumper;
	use Config::Grammar;

	my $RE_IP	= '\d+\.\d+\.\d+\.\d+';
	my $RE_MAC	= '[0-9a-f]{2}(?::[0-9a-f]{2}){5}';
	my $RE_HOST	= '\S+';

	my $parser = Config::Grammar->new({
	  _sections => [ 'network', 'hosts' ],
	  network => {
	     _vars     => [ 'dns' ],
	     _sections => [ "/$RE_IP/" ],
	     dns       => {
		_doc => "address of the dns server",
		_example => "ns1.oetiker.xs",
		_re => $RE_HOST,
		_re_error =>
		   'dns must be an host name or ip address',
		},
	     "/$RE_IP/" => {
		_doc	=> "Ip Adress",
		_example => '10.2.3.2',
		_vars	=> [ 'netmask', 'gateway' ],
		netmask => {
		   _doc => "Netmask",
		   _example => "255.255.255.0",
		   _re => $RE_IP,
		   _re_error =>
		      'netmask must be a dotted ip address'
		   },
		gateway => {
		   _doc => "Default Gateway address in IP notation",
		   _example => "10.22.12.1",
		   _re => $RE_IP,
		   _re_error =>
		      'gateway must be a dotted ip address' },
		},
	     },
	  hosts => {
	     _doc => "Details about the hosts",
	     _table  => {
		 _doc => "Description of all the Hosts",
		_key => 0,
		_columns => 3,
		0 => {
		   _doc => "Ethernet Address",
		   _example => "0:3:3:d:a:3:dd:a:cd",
		   _re => $RE_MAC,
		   _re_error =>
		      'first column must be an ethernet mac address',
		   },
		1 => {
		   _doc => "IP Address",
		   _example => "10.11.23.1",
		   _re => $RE_IP,
		   _re_error =>
		      'second column must be a dotted ip address',
		   },
		2 => {
		   _doc => "Host Name",
		   _example => "tardis",
		    },
		},
	     },
	  });

	my $cfg = $parser->parse('test.cfg') or
	  die "ERROR: $parser->{err}\n";
	print Dumper($cfg);
	print $parser->makepod;

       Configuration

	*** network ***

	  dns	   = 192.168.7.87

	+ 192.168.7.64

	  netmask  = 255.255.255.192
	  gateway  = 192.168.7.65

	*** hosts ***

	  00:50:fe:bc:65:11	192.168.7.97	plain.hades
	  00:50:fe:bc:65:12	192.168.7.98	isg.ee.hades
	  00:50:fe:bc:65:14	192.168.7.99	isg.ee.hades

       Result

	{
	  'hosts' => {
		       '00:50:fe:bc:65:11' => [
						'00:50:fe:bc:65:11',
						'192.168.7.97',
						'plain.hades'
					      ],
		       '00:50:fe:bc:65:12' => [
						'00:50:fe:bc:65:12',
						'192.168.7.98',
						'isg.ee.hades'
					      ],
		       '00:50:fe:bc:65:14' => [
						'00:50:fe:bc:65:14',
						'192.168.7.99',
						'isg.ee.hades'
					      ]
		     },
	  'network' => {
			 '192.168.7.64' => {
					     'netmask' => '255.255.255.192',
					     'gateway' => '192.168.7.65'
					   },
			 'dns' => '192.168.7.87'
		       }
	};

SEE ALSO
       Config::Grammar::Dynamic

COPYRIGHT
       Copyright (c) 2000-2005 by ETH Zurich. All rights reserved.  Copyright
       (c) 2007 by David Schweikert. All rights reserved.

LICENSE
       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

AUTHORS
       David Schweikert, Tobias Oetiker, Niko Tyni

perl v5.14.0			  2007-09-25		    Config::Grammar(3)
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