box-o-sand/ex20.rb

input_file = ARGV.first

def print_all(f)
  puts f.read
end

def rewind(f)
  f.seek(0, IO::SEEK_SET)
end

def print_a_line(line_count, f)
  puts "#{line_count} #{f.readline}"
end

current_file = File.open(input_file)

puts "First let's print the whole file:"
puts # a blank line

print_all(current_file)

puts "Now let's rewind, kind of like a tape."

rewind(current_file)

puts "Let's print three lines:"

current_line = 1
print_a_line(current_line, current_file)

current_line += 1
print_a_line(current_line, current_file)

current_line += 1
print_a_line(current_line, current_file)