Ruby: output not saved to file

I'm trying to give a file as input, have it changed within the program, and save the result to a file that is output. But the output file is the same as the input file. :/ Total n00b question, but what am I doing wrong?:

puts "Reading Celsius temperature value from data file..."
num = File.read("temperature.dat")
celsius = n开发者_如何学编程um.to_i
farenheit = (celsius * 9/5) + 32
puts "Saving result to output file 'faren_temp.out'"
fh = File.new("faren_temp.out", "w")
fh.puts farenheit
fh.close

I have tested the code on my machine and I have correctly the "faren_temp.out" file. Nothing is wrong ?

Temperature.dat

23

faren_temp.out

73

You just have a problem in the result. "celsius" must be a float variable in order to do a float division (not an int division).

puts "Reading Celsius temperature value from data file..."
num = File.read("temperature.dat")
celsius = num.to_f # modification here
farenheit = (celsius * 9/5) + 32
puts "Saving result to output file 'faren_temp.out'"
fh = File.new("faren_temp.out", "w")
fh.puts farenheit
fh.close

faren_temp.out

73.4

How about:

puts "Reading Celsius temperature value from data file..."
farenheit = 0.0
File.open("temperature.dat","r"){|f| farenheit = (f.read.to_f * 9/5) + 32}
puts "Saving result to output file 'faren_temp.out'"
File.open("faren_temp.out","w"){|f|f.write "#{farenheit}\n"}