Config::Grammar - A grammar-based, user-friendly config parser
use Config::Grammar;
my $args = { encoding => 'utf8' }; # the second parameter to parse() is optional
my $parser = Config::Grammar->new(\%grammar);
my $cfg = $parser->parse('app.cfg', $args) or die "ERROR: $parser->{err}\n";
my $pod = $parser->makepod();
my $ex = $parser->maketmpl('TOP','SubNode');
my $minex = $parser->maketmplmin('TOP','SubNode');
Config::Grammar is a module to parse configuration files. The optional second
parameter to the
parse() method can be used to specify the file
encoding to use for opening the file (see documentation for Perl's use open
pragma).
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.
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
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 occurrences 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
Assignments 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.
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 $args = { encoding => 'utf8' }; # the second parameter to parse() is optional
my $cfg = $parser->parse('test.cfg', $args) 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'
}
};
Config::Grammar::Dynamic
Copyright (c) 2000-2005 by ETH Zurich. All rights reserved. Copyright (c) 2007
by David Schweikert. All rights reserved.
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
David Schweikert, Tobias Oetiker, Niko Tyni