Update a configuration file: Difference between revisions

=={{header|Ruby}}==

<lang ruby>require 'stringio'

class ConfigFile

# create a ConfigFile object from a file

def self.file(filename)

fh = File.open(filename)

obj = self.new(fh)

obj.filename = filename

fh.close

obj

end

# create a ConfigFile object from a string

def self.data(string)

fh = StringIO.new(string)

obj = self.new(fh)

fh.close

obj

end

def initialize(filehandle)

@lines = filehandle.readlines

@filename = nil

tidy_file

end

attr :filename

def save()

if @filename

File.open(@filename, "w") {|f| f.write(self)}

end

end

def tidy_file()

@lines.map! do |line|

# remove leading whitespace

line.lstrip!

if line.match(/^#/)

# Lines beginning with hash symbols should not be manipulated and left

# unchanged in the revised file.

line

else

# replace double semicolon prefixes with just a single semicolon

line.sub!(/^;+\s+/, "; ")

if line.match(/^; \s*$/)

# Any lines beginning with a semicolon or groups of semicolons, but no

# following option should be removed

line = ""

else

# remove ... any trailing whitespace on the lines

line = line.rstrip + "\n"

# Whitespace between the option and paramters should consist only of a

# single space

if m = line.match(/^(; )?([[:upper:]]+)\s+(.*)/)

line = (m[1].nil? ? "" : m[1]) + format_line(m[2], m[3])

end

end

line

end

end

end

def format_line(option, value)

"%s%s\n" % [option.upcase.strip, value.nil? ? "" : " " + value.to_s.strip]

end

# returns the index of the option, or nil if not found

def find_option(option)

@lines.find_index {|line| line.match(/^#{option.upcase.strip}\b/)}

end

# uncomments a disabled option

def enable_option(option)

if idx = find_option("; " + option)

@lines[idx][/^; /] = ""

end

end

# comment a line with a semi-colon

def disable_option(option)

if idx = find_option(option)

@lines[idx][/^/] = "; "

end

end

# add an option, or change the value of an existing option.

# use nil for the value to set a boolean option

def set_value(option, value)

if idx = find_option(option)

@lines[idx] = format_line(option, value)

else

@lines << format_line(option, value)

end

end

def to_s

@lines.join('')

end

end

config = ConfigFile.data(DATA.read)

config.disable_option('needspeeling')

config.enable_option('seedsremoved')

config.set_value('numberofbananas', 1024)

config.set_value('numberofstrawberries', 62000)

puts config

__END__

# This is a configuration file in standard configuration file format

#

# Lines begininning with a hash or a semicolon are ignored by the application

# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.

# Remaining words or numbers on the line are configuration parameter

# data fields.

# Note that configuration option names are not case sensitive. However,

# configuration parameter data is case sensitive and the lettercase must

# be preserved.

# This is a favourite fruit

FAVOURITEFRUIT banana

# This is a boolean that should be set

NEEDSPEELING

# This boolean is commented out

;;; SEEDSREMOVED

;;;

# How many bananas we have

NUMBEROFBANANAS 48</lang>

outputs

<pre># This is a configuration file in standard configuration file format

#

# Lines begininning with a hash or a semicolon are ignored by the application

# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.

# Remaining words or numbers on the line are configuration parameter

# data fields.

# Note that configuration option names are not case sensitive. However,

# configuration parameter data is case sensitive and the lettercase must

# be preserved.

# This is a favourite fruit

FAVOURITEFRUIT banana

# This is a boolean that should be set

; NEEDSPEELING

# This boolean is commented out

SEEDSREMOVED

# How many bananas we have

NUMBEROFBANANAS 1024

NUMBEROFSTRAWBERRIES 62000</pre>