File Chopper

chop.rb

require "optparse"
require "ostruct"

class FileChopper
	Usage = "Usage:
  chop.rb FILE[S] [options]

Options:
  -f, [--front]                # Chop from the front
  -l, [--lines]                # Chop from each line
  -N, [--no-newlines]          # Do not preserve newlines in line mode
  -n, [--number=NUMBER]        # Number of characters to chop

  -p, [--pretend]              # Run but do not make any changes
  -q, [--quiet]                # Supress status output
  -V, [--verbose]              # Show extra output

  -h, [--help]                 # Show this help message and quit
  -v, [--version]              # Show chop.rb version number and quit

Description:
    This script will chop bytes from a file. The default is to chop one
    character from the end of the file. Any number of characters can be
    chopped from the beginning or end of the file or from each line.

Example:
    chop.rb myfile.txt -f -n 4

    This chops the first four characters from the file."

	Version = "0.1.0"

	def initialize
		@options = OpenStruct.new
		@file_list = []

		@options.files = []
		@options.back = true
		@options.front = false
		@options.lines = false
		@options.no_newlines = false
		@options.number = 1
		@options.pretend = false
		@options.quiet = false
		@options.verbose = false
		@options.help = false
		@options.version = false
	end

	def parse_options(argv)
		if argv.length == 0
			puts "Error: no file(s) given\n\n"
			puts Usage
			exit
		end

		begin
			op = OptionParser.new do |ops|
				ops.banner = Usage
				ops.separator ""

				ops.on("-f", "--front", "Chop from the front") do |front|
					@options.front = front
				end

				ops.on("-l", "--lines", "Chop from each line") do |lines|
					@options.lines = lines
				end

				ops.on("-N", "--no-newlines", "Do not preserve newlines in line mode") do |no_newlines|
					#no idea why this was coming through as false
					@options.no_newlines = true
				end

				ops.on("-n", "--number NUMBER", "Number of characters to chop") do |number|
					@options.number = number.to_i

					if @options.number < 1
						raise OptionParser::InvalidArgument, "number of characters must be >= 1"
					end
				end

				ops.on("-p", "--pretend", "Run but do not make any changes") do |pretend|
					@options.pretend = pretend
				end

				ops.on("-q", "--quiet", "Supress status output") do |quiet|
					@options.quiet = quiet
				end

				ops.on("-V", "--verbose", "Show extra output") do |verbose|
					@options.verbose = verbose
				end

				ops.on("-h", "--help", "Show this help message and quit") do |help|
					puts Usage
					exit
				end

				ops.on("-v", "--version", "Show chop.rb version number and quit") do |version|
					puts "chop.rb #{Version}"
					exit
				end
			end

			op.parse!(argv)
		rescue Exception => exception
			puts "Error: #{exception.message}\n\n"
			puts Usage
			exit
		end

		if argv.length == 0
			puts "Error: no file name given.\n\n"
			puts Usage
			exit
		end

		@file_list = argv
	end

	def chop
		@file_list.each do |file_name|
			print_message "Debug", file_name

			if @options.lines
				content = IO.readlines(file_name)
			else
				content = [open(file_name, "rb") { |file| file.read }]
			end

			result = ""

			content.each do |line|
				newline = false

				if @options.lines
					if line[-1, 1] == "\n"
						newline = true

						line = line[0, line.length - 1]
					end
				end

				print_message "Debug", line.gsub(/[[:cntrl:]]|[[:space:]]/, "_")

				if @options.number > line.length
					@options.number = line.length
				end

				if @options.front
					result << line[@options.number, line.length]
				else
					result << line[0, line.length - @options.number]
				end

				if @options.lines && !@options.no_newlines
					if result.length == 0
						result = "\n"
					else
						#if line[-1, 1] == "\n" && result[-1, 1] != "\n"
						if newline && result[-1, 1] != "\n"
							result << "\n"
						end
					end
				end
			end

			print_message "Debug", result.gsub(/[[:cntrl:]]|[[:space:]]/, "_")

			unless @options.pretend
				File.open(file_name, "wb") do |output|
					result.each_byte do |byte|
						output.print byte.chr
					end
				end
			end
		end
	end

	def print_message(type, message)
		if (type == "Error" || @options.verbose) && !@options.quiet
			puts "#{type}: #{message}"
		end
	end
end

file_chopper = FileChopper.new

file_chopper.parse_options(ARGV)

file_chopper.chop