Grep in files

grep.rb

DEBUG = false

if ARGV.size < 2
  puts "Usage: #$0 pattern file_pattern"
  puts "Example: #$0 '\\d+' '*.rb'"
  exit
end

dirname = File.dirname(ARGV[1])
file_pattern = File.basename(ARGV[1])
files = File.join(dirname, "**", file_pattern)
puts files if DEBUG
pattern = /#{ARGV[0]}/
Dir.glob(files) do |file|
  puts file if DEBUG
  if File.file?(file)
    lineno = 0
    File.open(file).each do |line|
      lineno += 1
      if line =~ pattern
        puts "#{file} (#{lineno}): #{line}"
      end
    end
  end
end