Making write to a file thread safe

Question

I have a function in a ruby file that writes to a file like this

File.open("myfile", 'a') { |f| f.puts("#{sometext}") }

This function is called in different threads, making file write such as the above not thread safe. Does anyone have any idea how to make this file write thread safe in the simplest way?

More Info: If it matters, I am using the rspec framework.

Answer 1

You could give a lock by File#flock

File.open("myfile", 'a') { |f| 
  f.flock(File::LOCK_EX)
  f.puts("#{sometext}") 
}

Answer 2

Referring to: http://blog.douglasfshearer.com/post/17547062422/threadsafe-file-consistency-in-ruby

def lock(path)
  # We need to check the file exists before we lock it.
  if File.exist?(path)
    File.open(path).flock(File::LOCK_EX)
  end

  # Carry out the operations.
  yield

  # Unlock the file.
  File.open(path).flock(File::LOCK_UN)
end

lock("myfile") do
  File.open("myfile", 'a') { |f| f.puts("#{sometext}") }
end