デシベルと比を変換する簡易スクリプト

dBconv.rb

#!/usr/bin/env ruby
#-*- encoding:utf-8 -*-

# 1.9じゃないとちゃんと動かないようだよ。

if ARGV.size != 2 then
	puts "dBconv -{n|v|w} n[dB|x]"
	exit 0
end

dB = 0
nx = 0

todB = false

m = 'n' # or v or w

ARGV.each do |x|
	if x =~ /dB$/ then
		dB = x[0..(x.size() - 3)].to_f
		if dB <= 0 then
			puts "input number is invalid."
			exit 1
		end
		todB = false
	end
	if x=~ /x$/ then
		nx = x[0..(x.size() -2)].to_f
		todB = true
	end

	if x=~ /^-/ then
		m = 'n' if x[1] == 'n'
		m = 'v' if x[1] == 'v'
		m = 'w' if x[1] == 'w'
	end
end

if todB == true then
	dB = Math::log10 nx
	if m == 'n' then
		puts "=#{dB}"
	elsif m == 'v' then
		puts "=#{dB*20}"
	elsif m == 'w' then
		puts "=#{dB*10}"
	end
else
	if m == 'n' then
		nx = 10.0 ** dB
	elsif m == 'v' then
		nx = 10.0 ** (dB / 20)
	elsif m == 'w' then
		nx = 10.0 ** (dB / 10)
	end
	puts "=#{nx}"
end