Andrew Wilcox > ConfigReader > ConfigReader::DirectiveStyle

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NAME ^

ConfigReader::DirectiveStyle

Reads a configuration file of directives and values.

CONFIGURATION FILE SYNOPSIS ^

    # comments start with a #, and blank lines are ignored
    
    Input     /etc/data_source      # the value follows the directive name
    HomePage  http://www.w3.org/
    
    # values can be quoted
    Comment   "here is a value with trailing spaces   "

CODE SYNOPSIS ^

    my $c = new ConfigReader::DirectiveStyle;
    
    directive $c 'Input', undef, '~/input';  # specify default value,
                                             #   but no parsing needed
    required  $c 'HomePage', 'new URI::URL'; # create URI::URL object
    ignore    $c 'Comment';                  # Ignore this directive.
    
    
    $c->load('my.config');
    open(IN, $c->value("Input"));
    
    $c->define_accessors();                  # creates Input() and HomePage()
    retrieve(HomePage());

DESCRIPTION ^

This class reads a common style of configuration files, where directive names are followed by a value. For each directive you can specify whether it has a default value or is required, and a function or method to use to parse the value. Errors and warnings are caught while parsing, and the location where the offending value came from (either from the configuration file, or your Perl source for default values) is reported.

DirectiveStyle is a subclass of ConfigReader::Values. The methods to define the directives in the configuration file are documented there.

Comments are introduced by the "#" character, and continue until the end of line. Like in Perl, the backslash character "\" may be used in the directive values for the various standard sequences:

     \t          tab
     \n          newline
     \r          return
     \f          form feed
     \v          vertical tab, whatever that is
     \b          backspace
     \a          alarm (bell)
     \e          escape
     \033        octal char
     \x1b        hex char

The value may also be quoted, which lets you include leading or trailing spaces. The quotes are stripped off before the value is returned.

DirectiveStyle itself only reads the configuration file. Most of the hard work of defining the directives and parsing the values is done in its superclass, ConfigReader::Values. You should be able to easily modify or subclass DirectiveStyle to read a different style of configuration file.

PUBLIC METHODS ^

new( [$spec] )

This static method creates and returns a new DirectiveStyle object. For information about the optional $spec argument, see DirectiveStyle::new().

load($file, [$untaint])

Before calling load(), you'll want to define the directives using the methods described in ConfigReader::Values.

Reads a configuration from $file. The default values for any directives not present in the file are assigned.

Normally configuration values are tainted like any data read from a file. If the configuration file comes from a trusted source, you can untaint all the values by setting the optional $untaint argument to a true value (such as 'UNTAINT').

SUBCLASSABLE METHODS ^

You can stop reading here if you just want to use DirectiveStyle. The following methods could be overridden in a subclass to provide additional or alternate functionality.

parse_line($line, $whence, $untaint)

Parses $line. $whence is a string describing the source of the line. Returns a two-element array of the directive and the value string, or the empty array () if the line is blank or only contains a comment.

parse_value_string($str, $whence)

Interprets quotes, backslashes, and comments in the value part. (Note that after the value string is returned, it will still get passed to the directive's parsing function of method if one is defined).

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