Config::Grammar(3pm) User Contributed Perl Documentation Config::Grammar(3pm)
NAME
Config::Grammar - A grammar-based, user-friendly config parser
SYNOPSIS
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');
DESCRIPTION
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.
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 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.
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 $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'
}
};
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 v5.34.0 2022-05-26 Config::Grammar(3pm)
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