Using grep from Ruby

find_num.rb

# original slow method to find a number plus a divider (|)
# at the start of a line
def find_num(file, num)
  found = false
  File.read(file).each do |line|
  if line.chomp.split('|', -1)[0] == num
    found = true
    break
  end
end

# new method that uses the system's grep
# since this calls the system, make sure that you trust the values
# of file and num
def find_num(file, num)
  found = false
  found = true if %x[grep -cm1 "^#{num}|" "#{file}"].chomp == '1'
  found
end