Makes a big file.

mkbigfile.rb

#!/usr/bin/env ruby
require 'optparse'
require 'ostruct'
require 'pp'

class MkBigFile
        attr_reader :name, :version, :options
        TYPES = %w[zero sparse]

        def initialize()
                @name = 'mkbigfile'
                @version = [0, 0, 1]
        end

        def parse(args)
                @options = OpenStruct.new
                @options.verbose = false
                @options.type = "sparse"

                type_list = TYPES.join(", ")
                opts = OptionParser.new do |opts|
                        opts.banner = @name + " " + @version.join('.') + "\nusage: mkbigfile.rb [options] -f <filename> -s <size>"
                        opts.separator ""
                        opts.separator "Specific options:"

                        opts.on("-v" , "--[no-]verbose", "Run in verbose mode") do |v|
                                @options.verbose = v
                        end
                        opts.on("-f", "--filename FILENAME", "Specify output filename") do |f|
                                @options.filename = f
                        end
                        opts.on("-s", "--size SIZE", Integer, "Specify file size (GB)") do |s|
                                @options.size = s
                                @options.sizeBytes = s * 1024 * 1024 * 1024
                        end
                        opts.on("-t", "--type TYPE", TYPES, "Set creation type (#{type_list})") do |type|
                                @options.type = type
                        end
                        opts.on("-h", "--help", "Show this message") do
                                puts opts
                                exit
                        end
                        opts.on_tail("--version", "Show version") do
                                puts @name + " " + @version.join('.')
                                exit
                        end
                end

                opts.parse!(args)
                opts

        end

        def info(message)
                if @options.verbose
                        puts message
                end
        end
end

# Get command line arguments
mbf = MkBigFile.new
mbf.parse(ARGV)

# Write a whole lotta 0s
File.open(mbf.options.filename, "wb+") do |file|
        mbf.info "Creating file"
        mbf.info "  Filename:  " + mbf.options.filename
        mbf.info "  Size:      " + mbf.options.size.to_s + " GB"
        mbf.info "  Size:      " + mbf.options.sizeBytes.to_s + " B"

        if mbf.options.type == "sparse"
                mbf.info "  Type:      Sparse"

                file.truncate(mbf.options.sizeBytes-1)
                file.putc 00
        elsif mbf.options.type == "zero"
                mbf.info "  Type:      Zeros"

                mbf.options.sizeBytes.times do
                        file.putc 00
                end
        else
                puts "error: unknown file type \"" + mbf.options.type + "\""
                exit
        end

        mbf.info "Done"
end