Count the files and lines of code in a directory tree.

gistfile1.rb

# Shell out to the fast and reliable `wc` utility.
def lines(path)
  # output of wc (returned by backticks) is formatted like this:
  # "     111 filename.ext"
  `wc -l #{path}`.strip.split(' ').first.to_i
end

# **/* gets all files and directories in all subdirectories.
files = Dir["/path/to/directory/**/*"]

# remove directories from the list (wc complains when you give it directories)
files.select! { |f| File.file?(f) }

# transform array of filepaths to an array of line counts, then sum them all up
total_lines_of_code = files.map { |f| lines(f) }.inject(:+)

number_of_files = files.size
average_lines_per_file = total_lines_of_code / number_of_files

puts "#{number_of_files} files"
puts "#{total_lines_of_code} total lines of code"
puts "#{average_lines_per_file} average lines of code per file"

If you want to pass the directory per parameter, replace line 9 by files = Dir[ARGV[0]], and - important - encapsulate the argument into strings (e.g. ./loc "/home/me/project/**/*.rb").