How to Calculate sum of all the digits in text file

I am having text file t.txt,I want to calculate sum of all the digits in text file Example

    --- t.txt ---
The rahul  jumped in 2 the well. The water was cold at 1 degree Centigrade. There were 3 grip holes on the walls.  The well was 17 feet deep.
--- EOF --

sum 2+1+3+1+7 My ruby code to calculate sum is

ruby -e "File.read('t.txt').split.inject(0){|mem, obj| mem += obj.to_f}"

But i am not getting any answer??