Read and write file atomically

Question

I\'d like to read and write a file atomically in Ruby between multiple independent Ruby processes (not threads).

• I found atomic_write from ActiveSupport. This

Answer 1

Take a look at transaction and open_and_lock_file methods in "pstore.rb" (Ruby stdlib).

YAML::Store works fine for me. So when I need to read/write atomically I (ab)use it to store data as a Hash.

Answer 2

You want to use File#flock in exclusive mode. Here's a little demo. Run this in two different terminal windows.

filename = 'test.txt'

File.open(filename, File::RDWR) do |file|
  file.flock(File::LOCK_EX)

  puts "content: #{file.read}"
  puts 'doing some heavy-lifting now'
  sleep(10)
end