txt2num: convert a 'telephone word' into raw numbers

gistfile1.rb

#!/usr/bin/env ruby

def txt2num str
  letters = {'a' => 2, 'b' => 2, 'c' => 2,
             'd' => 3, 'e' => 3, 'f' => 3,
             'g' => 4, 'h' => 4, 'i' => 4,
             'j' => 5, 'k' => 5, 'l' => 5,
             'm' => 6, 'n' => 6, 'o' => 6,
             'p' => 7, 'q' => 7, 'r' => 7, 's' => 7,
             't' => 8, 'u' => 8, 'v' => 8,
             'w' => 9, 'x' => 9, 'y' => 9, 'z' => 9}
  str.chars.map do |char|
    letters[char.downcase] || char
  end.join
end

if ARGV.empty?
  while gets
    print txt2num $_
  end
else
  ARGV.each {|word| puts txt2num word }
end