batch_perms.rb

#!/usr/bin/env ruby

WORKER_THREADS = 10

require "bundler"
Bundler.require

unless ARGV.size == 3
  puts "USAGE: cmd <s3 key> <s3 secret> <bucket name>"
  exit
end

marker = ""

AWS::S3::Base.establish_connection!(
  :access_key_id => ARGV[0],
  :secret_access_key => ARGV[1]
)

bucket = ARGV[2]

threads = []
queue = Queue.new

# Consumer
threads << Thread.new do
  loop do
    objects = Bucket.objects(bucket_name, :marker=>marker, :max_keys=>1000)
    break if objects.size == 0
    marker = objects.last.key
    
    objects.each do |obj|
      queue << obj.key
      # puts "#{obj.key}"
    end
  end
end

# worker
(1..WORKER_THREADS).each do |i|
  threads << Thread.new do
    item = queue.pop
    puts "Updating permissions for obj: " + item
    policy = S3Object.acl(item, bucket)
    policy.grants << ACL::Grant.grant(:public_read)
    S3Object.acl(item, bucket, policy)
    # SET PERMS
  end
end

threads.each {|t| t.join}

Gemfile

source :rubygems

gem "aws-s3", :require => 'aws/s3'