parse fastq files and filter out base on name

parse_fastq

#!/usr/bin/env ruby
# http://biostar.stackexchange.com/questions/10376/how-to-efficiently-parse-a-huge-fastq-file
# Usage: cat my.fastq | parse_fastq.rb list.txt
h = {} # hash with reads I am looking for
File.open(ARGV[0].to_s).each_line {|l| h["@" + l] = 1}
ln, f = [0, 0] # line number, flag
$stdin.each_line do |l|
  f = h[l] ? 1 : 0 if ln % 4 == 0
  puts l if f == 1
  ln = ln + 1
end