ファイル操作のメモ

1)

input	= File.open(input_filename, "r")
unless input.nil?
	output	= File.open(output_filename, "w")
	unless output.nil?
		# do something
		output.close
	end
	input.close
end

2)

File.open(input_filename, "r") { |input|
	File.open(output_filename, "w") { |output|
		# do something
	}
}

3)

begin
	input	= File.open(input_filename, "r")
	output	= File.open(output_filename, "w")
	# do something
rescue
	printf "error(#{$!})\n"
	exit 1
ensure
	unless output.nil?
		output.close
	end
	unless input.nil?
		input.close
	end
end